Eek!<\/h1>\r\n<\/div>\r\nBeing bitten on the nose by an eel certainly qualifies as a frightening experience! The fear this man is experiencing produces the same physiological responses in most people\u00a0\u2014\u00a0racing heart, rapid breathing, clammy hands. These and other [pb_glossary id=\"6013\"]fight-or-flight responses[\/pb_glossary]\u00a0prepare the body to either defend itself or run away from danger. Why does fear elicit these changes in the body? The responses occur in large part because of hormones secreted by the adrenal glands.\r\n\r\nIntroduction to the Adrenal Glands<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_3477\" align=\"alignleft\" width=\"529\"]![\"Adrenal](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Diagram_showing_where_the_adrenal_glands_are_in_the_body_CRUK_415.svg_-2.png\")
Figure 9.6.2 Each of the two adrenal glands is found above a kidney.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"5869\"]adrenal glands[\/pb_glossary]<\/strong> are endocrine glands that produce a variety of hormones. Adrenal hormones include the fight-or-flight hormone adrenaline and the steroid hormone cortisol. The two adrenal glands are located on both sides of the body, just above the kidneys, as shown in Figure 9.6.2. The right adrenal gland (on the left in the figure) is smaller and has a pyramidal shape. The left adrenal gland (on the right in the figure) is larger and has a half-moon shape.\r\n\r\nEach adrenal gland has two distinct parts, and each part has a different function, although both parts produce hormones. There is an outer layer, called the adrenal cortex, which produces steroid hormones including cortisol. There is also an inner layer, called the adrenal medulla, which produces non-steroid hormones including adrenaline.\r\n\r\nAdrenal Cortex<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"5867\"]adrenal cortex[\/pb_glossary],<\/strong> or outer layer of the adrenal gland, is divided into three additional layers, called zones (see Figure 9.6.3). Each zone has distinct enzymes that produce different hormones from the common precursor molecule cholesterol, which is a lipid.\r\n\r\n \t- [pb_glossary id=\"3480\"]Zona glomerulosa[\/pb_glossary]<\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\r\n \t
- [pb_glossary id=\"3481\"]Zona fasciculata[\/pb_glossary]<\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\r\n \t
- [pb_glossary id=\"3482\"]Zona reticularis[\/pb_glossary]<\/strong>\u00a0is the innermost layer of the adrenal cortex. It is directly adjacent to the medulla of the adrenal gland.<\/li>\r\n<\/ol>\r\n[caption id=\"attachment_3479\" align=\"aligncenter\" width=\"778\"]
![\"Adrenal](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/Adrenal_cortex_labelled-2.jpg\")
Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em>[\/caption]\r\n\r\n \r\n\r\n\r\nTypes of Adrenal Cortex Hormones<\/span>\r\n\r\n<\/div>\r\nHormones produced by the adrenal cortex are\u00a0known\u00a0by the general term\u00a0[pb_glossary id=\"5957\"]corticosteroids[\/pb_glossary].<\/strong> As [pb_glossary id=\"3423\"]steroid hormones[\/pb_glossary], corticosteroids are endocrine hormones that are made of [pb_glossary id=\"5651\"]lipids[\/pb_glossary] and exert their effects on [pb_glossary id=\"3422\"]target cells[\/pb_glossary] by crossing the [pb_glossary id=\"5489\"]plasma membrane[\/pb_glossary] and binding with receptors within the cytoplasm. A steroid hormone and its receptor form a complex that enters the cell [pb_glossary id=\"5797\"]nucleus[\/pb_glossary] and affects [pb_glossary id=\"6031\"]gene expression[\/pb_glossary]. There are three types of corticosteroids synthesized and secreted by the adrenal cortex. Each type is produced by a different zone of the adrenal cortex, as shown in Figure 9.6.4.\r\n\r\n[caption id=\"attachment_3484\" align=\"alignnone\" width=\"1102\"]![\"The](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/The_Adrenal_Glands-2.jpg\")
Figure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em>[\/caption]\r\nMineralocorticoids<\/h3>\r\nMineralocorticoids are produced in the [pb_glossary id=\"3480\"]zona glomerulosa[\/pb_glossary] and include the hormone [pb_glossary id=\"5881\"]aldosterone[\/pb_glossary]. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.\r\nGlucocorticoids<\/h3>\r\nGlucocorticoids are produced in the [pb_glossary id=\"3481\"]zona fasciculata[\/pb_glossary] and include the hormone\u00a0[pb_glossary id=\"5959\"]cortisol[\/pb_glossary],\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of [pb_glossary id=\"5813\"]proteins[\/pb_glossary], fats, and sugars. In general, they increase the level of [pb_glossary id=\"5451\"]glucose[\/pb_glossary] and [pb_glossary id=\"5657\"]fatty acids[\/pb_glossary] circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.\r\nAndrogens<\/h3>\r\n[pb_glossary id=\"3485\"]Androgens[\/pb_glossary]<\/strong>\u00a0are produced in the[pb_glossary id=\"3482\"] zona reticularis[\/pb_glossary] and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as [pb_glossary id=\"3409\"]testosterone[\/pb_glossary] in the male gonads ([pb_glossary id=\"3486\"]testes[\/pb_glossary]). In adult females, they are converted to female sex hormones called [pb_glossary id=\"5995\"]estrogens[\/pb_glossary]\u00a0in the female gonads ([pb_glossary id=\"3487\"]ovaries[\/pb_glossary]).\r\nRegulation of Adrenal Cortex Hormones<\/h2>\r\n[pb_glossary id=\"3423\"]Steroid hormone[\/pb_glossary] production by the three zones of the adrenal cortex is regulated by hormones secreted by the [pb_glossary id=\"5887\"]anterior[\/pb_glossary] lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide [pb_glossary id=\"2955\"]negative feedback[\/pb_glossary] to the [pb_glossary id=\"2937\"]hypothalamus[\/pb_glossary] and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.\r\n\r\n[caption id=\"attachment_3488\" align=\"aligncenter\" width=\"652\"]![\"ACTH](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/ACTH-negative-feedback-loop-2.png\")
Figure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em>[\/caption]\r\n\r\n\r\nAdrenal Medulla<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary]<\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0[pb_glossary id=\"5929\"]catecholamines[\/pb_glossary]<\/strong>, and they include\u00a0[pb_glossary id=\"5875\"]adrenaline[\/pb_glossary]<\/strong>\u00a0(also called epinephrine) and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary] (also called norepinephrine). These water-soluble, [pb_glossary id=\"3425\"]non-steroid hormones[\/pb_glossary]\u00a0are made of [pb_glossary id=\"5707\"]amino acids[\/pb_glossary]. As non-steroid hormones, they cannot cross the [pb_glossary id=\"5489\"]plasma membrane[\/pb_glossary] of [pb_glossary id=\"3422\"]target cells[\/pb_glossary]. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.\r\n\r\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the [pb_glossary id=\"3015\"]sympathetic division[\/pb_glossary] of the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary].\r\n\r\nDisorders of the Adrenal Glands<\/h1>\r\n<\/div>\r\nDisorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.\r\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\r\nHypersecretion of the glucocorticoid hormone [pb_glossary id=\"5959\"]cortisol[\/pb_glossary] leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary].<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.\r\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\r\n[caption id=\"attachment_3494\" align=\"alignleft\" width=\"475\"]![\"Addison's](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/A_69-Year-Old_Female_with_Tiredness_and_a_Persistent_Tan_01-2.png\")
Figure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em>[\/caption]\r\n\r\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary].<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.\r\n\r\nFeature: My Human Body<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_3495\" align=\"aligncenter\" width=\"877\"]![\"\"](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2023\/10\/BASE_Jumping_from_Sapphire_Tower_in_Istanbul-2.jpg\")
Figure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline \"junkie's\" day!\u00a0<\/em>[\/caption]\r\n\r\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.\r\n\r\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.\r\n\r\nAdrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.\r\n\r\nWhile some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.\r\n\r\n\r\n9.6 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5869\"]adrenal glands[\/pb_glossary]\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the [pb_glossary id=\"5867\"]adrenal cortex[\/pb_glossary] and an inner layer called the [pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary].<\/li>\r\n \t
- The adrenal cortex produces steroid hormones called by the general term [pb_glossary id=\"5957\"]corticosteroids[\/pb_glossary], of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and [pb_glossary id=\"3485\"]androgens[\/pb_glossary]\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\r\n \t
- The adrenal medulla produces non-steroid catecholamine hormones, including [pb_glossary id=\"5875\"]adrenaline[\/pb_glossary] and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary]. These hormones stimulate the [pb_glossary id=\"6013\"]fight-or-flight response[\/pb_glossary].<\/li>\r\n \t
- Disorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include [pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary], in which there is hypersecretion of cortisol, and [pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary], in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the structure and location of the adrenal glands.<\/li>\r\n \t
- [h5p id=\"577\"]<\/li>\r\n \t
- Compare and contrast the adrenal cortex and adrenal medulla.<\/li>\r\n \t
- Identify the three layers of the adrenal cortex and the type of hormones each layer produces.<\/li>\r\n \t
- Give an example of each type of corticosteroid and state its function.<\/li>\r\n \t
- Explain how the production of glucocorticoids is regulated.<\/li>\r\n \t
- What is a catecholamine? Give an example of a catecholamine and state its function.<\/li>\r\n \t
- Compare and contrast Cushing\u2019s syndrome and Addison\u2019s disease.<\/li>\r\n \t
- What are two ways in which the nervous system (which includes the brain, spinal cord, and nerves) controls the adrenal gland?<\/li>\r\n \t
- Explain why a pituitary tumor can cause either hypersecretion or hyposecretion of cortisol.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU\r\nHow stress affects your body - Sharon Horesh Bergquist, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=WuyPuH9ojCE&feature=emb_logo\r\n
How stress affects your brain - Madhumita Murgia, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=emb_logo\r\n
Adrenaline: Fight or Flight Response, Henk van 't Klooster, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 9.6.1<\/strong>\r\n\r\nAttack from wikimedia commons<\/a> by Jerry Kirkhart<\/a> from Los Osos, Calif. on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 9.6.2<\/strong>\r\n\r\nDiagram_showing_where_the_adrenal_glands_are_in_the_body_CRUK_415.svg<\/a> by Cancer Research UK uploader<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 9.6.3<\/strong>\r\n\r\nAdrenal_cortex_labelled<\/a> by Jpogi<\/a>\u00a0at\u00a0English Wikipedia<\/a> on Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en) license.\r\n\r\nFigure 9.6.4<\/strong>\r\n\r\nThe_Adrenal_Glands<\/a> by OpenStax College<\/a> is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.5<\/strong>\r\n\r\nACTH negative feedback loop by Christinelmiller is used under a\u00a0CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.6<\/strong>\r\n\r\nA_69-Year-Old_Female_with_Tiredness_and_a_Persistent_Tan_01<\/a>\u00a0by Petros Perros<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.5\/deed.en) license.\r\n\r\nFigure 9.6.7<\/strong>\r\n\r\nBASE_Jumping_from_Sapphire_Tower_in_Istanbul<\/a> by Kontizas Dimitrios on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/3.0) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 17.17 Adrenal glands [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 17.6). OpenStax College. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/17-6-the-adrenal-glands<\/p>\r\nHenk van 't Klooster. (2013). Adrenaline: Fight or flight response. YouTube. https:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=youtu.be<\/p>\r\n
Perros, P. (2005). A 69-year-old female with tiredness and a persistent tan. PLoS Medicine,<\/em> 2(8): e229. https:\/\/doi.org\/10.1371\/journal.pmed.0020229<\/p>\r\nTED-Ed. (2015, October 22). How stress affects your body - Sharon Horesh Bergquist. YouTube. https:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, November 6). How stress affects your brain - Madhumita Murgia. YouTube. https:\/\/www.youtube.com\/watch?v=WuyPuH9ojCE&feature=youtu.be<\/p>\r\n \r\n\r\n ","rendered":"
<\/p>\n![\"9.6.1](\"https:\/\/pressbooks.ccconline.org\/acchumanbio\/wp-content\/uploads\/sites\/152\/2019\/06\/Attack-from-wikimedia-commons-2.jpg\")
Figure 9.6.1 Got your nose!<\/em><\/figcaption><\/figure>\n\nEek!<\/h1>\n<\/div>\n
Being bitten on the nose by an eel certainly qualifies as a frightening experience! The fear this man is experiencing produces the same physiological responses in most people\u00a0\u2014\u00a0racing heart, rapid breathing, clammy hands. These and other fight-or-flight responses<\/a>\u00a0prepare the body to either defend itself or run away from danger. Why does fear elicit these changes in the body? The responses occur in large part because of hormones secreted by the adrenal glands.<\/p>\n\nIntroduction to the Adrenal Glands<\/h1>\n<\/div>\nFigure 9.6.2 Each of the two adrenal glands is found above a kidney.<\/em><\/figcaption><\/figure>\nThe\u00a0adrenal glands<\/a><\/strong> are endocrine glands that produce a variety of hormones. Adrenal hormones include the fight-or-flight hormone adrenaline and the steroid hormone cortisol. The two adrenal glands are located on both sides of the body, just above the kidneys, as shown in Figure 9.6.2. The right adrenal gland (on the left in the figure) is smaller and has a pyramidal shape. The left adrenal gland (on the right in the figure) is larger and has a half-moon shape.<\/p>\nEach adrenal gland has two distinct parts, and each part has a different function, although both parts produce hormones. There is an outer layer, called the adrenal cortex, which produces steroid hormones including cortisol. There is also an inner layer, called the adrenal medulla, which produces non-steroid hormones including adrenaline.<\/p>\n
\nAdrenal Cortex<\/h1>\n<\/div>\n
The\u00a0adrenal cortex<\/a>,<\/strong> or outer layer of the adrenal gland, is divided into three additional layers, called zones (see Figure 9.6.3). Each zone has distinct enzymes that produce different hormones from the common precursor molecule cholesterol, which is a lipid.<\/p>\n\n- Zona glomerulosa<\/a><\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\n
- Zona fasciculata<\/a><\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\n
- Zona reticularis<\/a><\/strong>\u00a0is the innermost layer of the adrenal cortex. It is directly adjacent to the medulla of the adrenal gland.<\/li>\n<\/ol>\n
Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em><\/figcaption><\/figure>\n <\/p>\n
\nTypes of Adrenal Cortex Hormones<\/span><\/p>\n<\/div>\nHormones produced by the adrenal cortex are\u00a0known\u00a0by the general term\u00a0corticosteroids<\/a>.<\/strong> As steroid hormones<\/a>, corticosteroids are endocrine hormones that are made of lipids<\/a> and exert their effects on target cells<\/a> by crossing the plasma membrane<\/a> and binding with receptors within the cytoplasm. A steroid hormone and its receptor form a complex that enters the cell nucleus<\/a> and affects gene expression<\/a>. There are three types of corticosteroids synthesized and secreted by the adrenal cortex. Each type is produced by a different zone of the adrenal cortex, as shown in Figure 9.6.4.<\/p>\nFigure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em><\/figcaption><\/figure>\nMineralocorticoids<\/h3>\n
Mineralocorticoids are produced in the zona glomerulosa<\/a> and include the hormone aldosterone<\/a>. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.<\/p>\nGlucocorticoids<\/h3>\n
Glucocorticoids are produced in the zona fasciculata<\/a> and include the hormone\u00a0cortisol<\/a>,\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of proteins<\/a>, fats, and sugars. In general, they increase the level of glucose<\/a> and fatty acids<\/a> circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.<\/p>\nAndrogens<\/h3>\n
Androgens<\/a><\/strong>\u00a0are produced in the zona reticularis<\/a> and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as testosterone<\/a> in the male gonads (testes<\/a>). In adult females, they are converted to female sex hormones called estrogens<\/a>\u00a0in the female gonads (ovaries<\/a>).<\/p>\nRegulation of Adrenal Cortex Hormones<\/h2>\n
Steroid hormone<\/a> production by the three zones of the adrenal cortex is regulated by hormones secreted by the anterior<\/a> lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide negative feedback<\/a> to the hypothalamus<\/a> and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.<\/p>\nFigure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em><\/figcaption><\/figure>\n\nAdrenal Medulla<\/h1>\n<\/div>\n
The\u00a0adrenal medulla<\/a><\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0catecholamines<\/a><\/strong>, and they include\u00a0adrenaline<\/a><\/strong>\u00a0(also called epinephrine) and noradrenaline<\/a> (also called norepinephrine). These water-soluble, non-steroid hormones<\/a>\u00a0are made of amino acids<\/a>. As non-steroid hormones, they cannot cross the plasma membrane<\/a> of target cells<\/a>. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.<\/p>\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the sympathetic division<\/a> of the autonomic nervous system<\/a>.<\/p>\n\nDisorders of the Adrenal Glands<\/h1>\n<\/div>\n
Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.<\/p>\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\n
Hypersecretion of the glucocorticoid hormone cortisol<\/a> leads to a disorder\u00a0called\u00a0Cushing\u2019s syndrome<\/a>.<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.<\/p>\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\nFigure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em><\/figcaption><\/figure>\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0Addison\u2019s disease<\/a>.<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.<\/p>\n\nFeature: My Human Body<\/h1>\n<\/div>\nFigure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline “junkie’s” day!\u00a0<\/em><\/figcaption><\/figure>\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.<\/p>\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.<\/p>\n
Adrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.<\/p>\n
While some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.<\/p>\n
\n\n\n9.6 Summary<\/span><\/h1>\n<\/header>\n\n\n- The adrenal glands<\/a>\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the adrenal cortex<\/a> and an inner layer called the adrenal medulla<\/a>.<\/li>\n
- The adrenal cortex produces steroid hormones called by the general term corticosteroids<\/a>, of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and androgens<\/a>\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\n
- The adrenal medulla produces non-steroid catecholamine hormones, including adrenaline<\/a> and noradrenaline<\/a>. These hormones stimulate the fight-or-flight response<\/a>.<\/li>\n
- Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include Cushing\u2019s syndrome<\/a>, in which there is hypersecretion of cortisol, and Addison\u2019s disease<\/a>, in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n9.6 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the structure and location of the adrenal glands.<\/li>\n
- \n\n
Introduction to the Adrenal Glands<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_3477\" align=\"alignleft\" width=\"529\"] Figure 9.6.2 Each of the two adrenal glands is found above a kidney.<\/em>[\/caption]\r\n\r\nThe\u00a0[pb_glossary id=\"5869\"]adrenal glands[\/pb_glossary]<\/strong> are endocrine glands that produce a variety of hormones. Adrenal hormones include the fight-or-flight hormone adrenaline and the steroid hormone cortisol. The two adrenal glands are located on both sides of the body, just above the kidneys, as shown in Figure 9.6.2. The right adrenal gland (on the left in the figure) is smaller and has a pyramidal shape. The left adrenal gland (on the right in the figure) is larger and has a half-moon shape.\r\n\r\nEach adrenal gland has two distinct parts, and each part has a different function, although both parts produce hormones. There is an outer layer, called the adrenal cortex, which produces steroid hormones including cortisol. There is also an inner layer, called the adrenal medulla, which produces non-steroid hormones including adrenaline.\r\n\r\nAdrenal Cortex<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"5867\"]adrenal cortex[\/pb_glossary],<\/strong> or outer layer of the adrenal gland, is divided into three additional layers, called zones (see Figure 9.6.3). Each zone has distinct enzymes that produce different hormones from the common precursor molecule cholesterol, which is a lipid.\r\n\r\n \t- [pb_glossary id=\"3480\"]Zona glomerulosa[\/pb_glossary]<\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\r\n \t
- [pb_glossary id=\"3481\"]Zona fasciculata[\/pb_glossary]<\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\r\n \t
- [pb_glossary id=\"3482\"]Zona reticularis[\/pb_glossary]<\/strong>\u00a0is the innermost layer of the adrenal cortex. It is directly adjacent to the medulla of the adrenal gland.<\/li>\r\n<\/ol>\r\n[caption id=\"attachment_3479\" align=\"aligncenter\" width=\"778\"] Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em>[\/caption]\r\n\r\n \r\n\r\n\r\nTypes of Adrenal Cortex Hormones<\/span>\r\n\r\n<\/div>\r\nHormones produced by the adrenal cortex are\u00a0known\u00a0by the general term\u00a0[pb_glossary id=\"5957\"]corticosteroids[\/pb_glossary].<\/strong> As [pb_glossary id=\"3423\"]steroid hormones[\/pb_glossary], corticosteroids are endocrine hormones that are made of [pb_glossary id=\"5651\"]lipids[\/pb_glossary] and exert their effects on [pb_glossary id=\"3422\"]target cells[\/pb_glossary] by crossing the [pb_glossary id=\"5489\"]plasma membrane[\/pb_glossary] and binding with receptors within the cytoplasm. A steroid hormone and its receptor form a complex that enters the cell [pb_glossary id=\"5797\"]nucleus[\/pb_glossary] and affects [pb_glossary id=\"6031\"]gene expression[\/pb_glossary]. There are three types of corticosteroids synthesized and secreted by the adrenal cortex. Each type is produced by a different zone of the adrenal cortex, as shown in Figure 9.6.4.\r\n\r\n[caption id=\"attachment_3484\" align=\"alignnone\" width=\"1102\"] Figure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em>[\/caption]\r\n
Mineralocorticoids<\/h3>\r\nMineralocorticoids are produced in the [pb_glossary id=\"3480\"]zona glomerulosa[\/pb_glossary] and include the hormone [pb_glossary id=\"5881\"]aldosterone[\/pb_glossary]. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.\r\nGlucocorticoids<\/h3>\r\nGlucocorticoids are produced in the [pb_glossary id=\"3481\"]zona fasciculata[\/pb_glossary] and include the hormone\u00a0[pb_glossary id=\"5959\"]cortisol[\/pb_glossary],\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of [pb_glossary id=\"5813\"]proteins[\/pb_glossary], fats, and sugars. In general, they increase the level of [pb_glossary id=\"5451\"]glucose[\/pb_glossary] and [pb_glossary id=\"5657\"]fatty acids[\/pb_glossary] circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.\r\nAndrogens<\/h3>\r\n[pb_glossary id=\"3485\"]Androgens[\/pb_glossary]<\/strong>\u00a0are produced in the[pb_glossary id=\"3482\"] zona reticularis[\/pb_glossary] and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as [pb_glossary id=\"3409\"]testosterone[\/pb_glossary] in the male gonads ([pb_glossary id=\"3486\"]testes[\/pb_glossary]). In adult females, they are converted to female sex hormones called [pb_glossary id=\"5995\"]estrogens[\/pb_glossary]\u00a0in the female gonads ([pb_glossary id=\"3487\"]ovaries[\/pb_glossary]).\r\nRegulation of Adrenal Cortex Hormones<\/h2>\r\n[pb_glossary id=\"3423\"]Steroid hormone[\/pb_glossary] production by the three zones of the adrenal cortex is regulated by hormones secreted by the [pb_glossary id=\"5887\"]anterior[\/pb_glossary] lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide [pb_glossary id=\"2955\"]negative feedback[\/pb_glossary] to the [pb_glossary id=\"2937\"]hypothalamus[\/pb_glossary] and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.\r\n\r\n[caption id=\"attachment_3488\" align=\"aligncenter\" width=\"652\"] Figure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em>[\/caption]\r\n\r\n\r\nAdrenal Medulla<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary]<\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0[pb_glossary id=\"5929\"]catecholamines[\/pb_glossary]<\/strong>, and they include\u00a0[pb_glossary id=\"5875\"]adrenaline[\/pb_glossary]<\/strong>\u00a0(also called epinephrine) and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary] (also called norepinephrine). These water-soluble, [pb_glossary id=\"3425\"]non-steroid hormones[\/pb_glossary]\u00a0are made of [pb_glossary id=\"5707\"]amino acids[\/pb_glossary]. As non-steroid hormones, they cannot cross the [pb_glossary id=\"5489\"]plasma membrane[\/pb_glossary] of [pb_glossary id=\"3422\"]target cells[\/pb_glossary]. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.\r\n\r\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the [pb_glossary id=\"3015\"]sympathetic division[\/pb_glossary] of the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary].\r\n\r\nDisorders of the Adrenal Glands<\/h1>\r\n<\/div>\r\nDisorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.\r\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\r\nHypersecretion of the glucocorticoid hormone [pb_glossary id=\"5959\"]cortisol[\/pb_glossary] leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary].<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.\r\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\r\n[caption id=\"attachment_3494\" align=\"alignleft\" width=\"475\"] Figure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em>[\/caption]\r\n\r\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary].<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.\r\n\r\nFeature: My Human Body<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_3495\" align=\"aligncenter\" width=\"877\"] Figure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline \"junkie's\" day!\u00a0<\/em>[\/caption]\r\n\r\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.\r\n\r\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.\r\n\r\nAdrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.\r\n\r\nWhile some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.\r\n\r\n\r\n9.6 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5869\"]adrenal glands[\/pb_glossary]\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the [pb_glossary id=\"5867\"]adrenal cortex[\/pb_glossary] and an inner layer called the [pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary].<\/li>\r\n \t
- The adrenal cortex produces steroid hormones called by the general term [pb_glossary id=\"5957\"]corticosteroids[\/pb_glossary], of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and [pb_glossary id=\"3485\"]androgens[\/pb_glossary]\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\r\n \t
- The adrenal medulla produces non-steroid catecholamine hormones, including [pb_glossary id=\"5875\"]adrenaline[\/pb_glossary] and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary]. These hormones stimulate the [pb_glossary id=\"6013\"]fight-or-flight response[\/pb_glossary].<\/li>\r\n \t
- Disorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include [pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary], in which there is hypersecretion of cortisol, and [pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary], in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the structure and location of the adrenal glands.<\/li>\r\n \t
- [h5p id=\"577\"]<\/li>\r\n \t
- Compare and contrast the adrenal cortex and adrenal medulla.<\/li>\r\n \t
- Identify the three layers of the adrenal cortex and the type of hormones each layer produces.<\/li>\r\n \t
- Give an example of each type of corticosteroid and state its function.<\/li>\r\n \t
- Explain how the production of glucocorticoids is regulated.<\/li>\r\n \t
- What is a catecholamine? Give an example of a catecholamine and state its function.<\/li>\r\n \t
- Compare and contrast Cushing\u2019s syndrome and Addison\u2019s disease.<\/li>\r\n \t
- What are two ways in which the nervous system (which includes the brain, spinal cord, and nerves) controls the adrenal gland?<\/li>\r\n \t
- Explain why a pituitary tumor can cause either hypersecretion or hyposecretion of cortisol.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU\r\nHow stress affects your body - Sharon Horesh Bergquist, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=WuyPuH9ojCE&feature=emb_logo\r\n
How stress affects your brain - Madhumita Murgia, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=emb_logo\r\n
Adrenaline: Fight or Flight Response, Henk van 't Klooster, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 9.6.1<\/strong>\r\n\r\nAttack from wikimedia commons<\/a> by Jerry Kirkhart<\/a> from Los Osos, Calif. on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 9.6.2<\/strong>\r\n\r\nDiagram_showing_where_the_adrenal_glands_are_in_the_body_CRUK_415.svg<\/a> by Cancer Research UK uploader<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 9.6.3<\/strong>\r\n\r\nAdrenal_cortex_labelled<\/a> by Jpogi<\/a>\u00a0at\u00a0English Wikipedia<\/a> on Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en) license.\r\n\r\nFigure 9.6.4<\/strong>\r\n\r\nThe_Adrenal_Glands<\/a> by OpenStax College<\/a> is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.5<\/strong>\r\n\r\nACTH negative feedback loop by Christinelmiller is used under a\u00a0CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.6<\/strong>\r\n\r\nA_69-Year-Old_Female_with_Tiredness_and_a_Persistent_Tan_01<\/a>\u00a0by Petros Perros<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.5\/deed.en) license.\r\n\r\nFigure 9.6.7<\/strong>\r\n\r\nBASE_Jumping_from_Sapphire_Tower_in_Istanbul<\/a> by Kontizas Dimitrios on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/3.0) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 17.17 Adrenal glands [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 17.6). OpenStax College. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/17-6-the-adrenal-glands<\/p>\r\nHenk van 't Klooster. (2013). Adrenaline: Fight or flight response. YouTube. https:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=youtu.be<\/p>\r\n
Perros, P. (2005). A 69-year-old female with tiredness and a persistent tan. PLoS Medicine,<\/em> 2(8): e229. https:\/\/doi.org\/10.1371\/journal.pmed.0020229<\/p>\r\nTED-Ed. (2015, October 22). How stress affects your body - Sharon Horesh Bergquist. YouTube. https:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, November 6). How stress affects your brain - Madhumita Murgia. YouTube. https:\/\/www.youtube.com\/watch?v=WuyPuH9ojCE&feature=youtu.be<\/p>\r\n \r\n\r\n ","rendered":"
<\/p>\nFigure 9.6.1 Got your nose!<\/em><\/figcaption><\/figure>\n\nEek!<\/h1>\n<\/div>\n
Being bitten on the nose by an eel certainly qualifies as a frightening experience! The fear this man is experiencing produces the same physiological responses in most people\u00a0\u2014\u00a0racing heart, rapid breathing, clammy hands. These and other fight-or-flight responses<\/a>\u00a0prepare the body to either defend itself or run away from danger. Why does fear elicit these changes in the body? The responses occur in large part because of hormones secreted by the adrenal glands.<\/p>\n\nIntroduction to the Adrenal Glands<\/h1>\n<\/div>\nFigure 9.6.2 Each of the two adrenal glands is found above a kidney.<\/em><\/figcaption><\/figure>\nThe\u00a0adrenal glands<\/a><\/strong> are endocrine glands that produce a variety of hormones. Adrenal hormones include the fight-or-flight hormone adrenaline and the steroid hormone cortisol. The two adrenal glands are located on both sides of the body, just above the kidneys, as shown in Figure 9.6.2. The right adrenal gland (on the left in the figure) is smaller and has a pyramidal shape. The left adrenal gland (on the right in the figure) is larger and has a half-moon shape.<\/p>\nEach adrenal gland has two distinct parts, and each part has a different function, although both parts produce hormones. There is an outer layer, called the adrenal cortex, which produces steroid hormones including cortisol. There is also an inner layer, called the adrenal medulla, which produces non-steroid hormones including adrenaline.<\/p>\n
\nAdrenal Cortex<\/h1>\n<\/div>\n
The\u00a0adrenal cortex<\/a>,<\/strong> or outer layer of the adrenal gland, is divided into three additional layers, called zones (see Figure 9.6.3). Each zone has distinct enzymes that produce different hormones from the common precursor molecule cholesterol, which is a lipid.<\/p>\n\n- Zona glomerulosa<\/a><\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\n
- Zona fasciculata<\/a><\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\n
- Zona reticularis<\/a><\/strong>\u00a0is the innermost layer of the adrenal cortex. It is directly adjacent to the medulla of the adrenal gland.<\/li>\n<\/ol>\n
Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em><\/figcaption><\/figure>\n <\/p>\n
\nTypes of Adrenal Cortex Hormones<\/span><\/p>\n<\/div>\nHormones produced by the adrenal cortex are\u00a0known\u00a0by the general term\u00a0corticosteroids<\/a>.<\/strong> As steroid hormones<\/a>, corticosteroids are endocrine hormones that are made of lipids<\/a> and exert their effects on target cells<\/a> by crossing the plasma membrane<\/a> and binding with receptors within the cytoplasm. A steroid hormone and its receptor form a complex that enters the cell nucleus<\/a> and affects gene expression<\/a>. There are three types of corticosteroids synthesized and secreted by the adrenal cortex. Each type is produced by a different zone of the adrenal cortex, as shown in Figure 9.6.4.<\/p>\nFigure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em><\/figcaption><\/figure>\nMineralocorticoids<\/h3>\n
Mineralocorticoids are produced in the zona glomerulosa<\/a> and include the hormone aldosterone<\/a>. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.<\/p>\nGlucocorticoids<\/h3>\n
Glucocorticoids are produced in the zona fasciculata<\/a> and include the hormone\u00a0cortisol<\/a>,\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of proteins<\/a>, fats, and sugars. In general, they increase the level of glucose<\/a> and fatty acids<\/a> circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.<\/p>\nAndrogens<\/h3>\n
Androgens<\/a><\/strong>\u00a0are produced in the zona reticularis<\/a> and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as testosterone<\/a> in the male gonads (testes<\/a>). In adult females, they are converted to female sex hormones called estrogens<\/a>\u00a0in the female gonads (ovaries<\/a>).<\/p>\nRegulation of Adrenal Cortex Hormones<\/h2>\n
Steroid hormone<\/a> production by the three zones of the adrenal cortex is regulated by hormones secreted by the anterior<\/a> lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide negative feedback<\/a> to the hypothalamus<\/a> and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.<\/p>\nFigure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em><\/figcaption><\/figure>\n\nAdrenal Medulla<\/h1>\n<\/div>\n
The\u00a0adrenal medulla<\/a><\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0catecholamines<\/a><\/strong>, and they include\u00a0adrenaline<\/a><\/strong>\u00a0(also called epinephrine) and noradrenaline<\/a> (also called norepinephrine). These water-soluble, non-steroid hormones<\/a>\u00a0are made of amino acids<\/a>. As non-steroid hormones, they cannot cross the plasma membrane<\/a> of target cells<\/a>. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.<\/p>\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the sympathetic division<\/a> of the autonomic nervous system<\/a>.<\/p>\n\nDisorders of the Adrenal Glands<\/h1>\n<\/div>\n
Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.<\/p>\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\n
Hypersecretion of the glucocorticoid hormone cortisol<\/a> leads to a disorder\u00a0called\u00a0Cushing\u2019s syndrome<\/a>.<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.<\/p>\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\nFigure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em><\/figcaption><\/figure>\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0Addison\u2019s disease<\/a>.<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.<\/p>\n\nFeature: My Human Body<\/h1>\n<\/div>\nFigure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline “junkie’s” day!\u00a0<\/em><\/figcaption><\/figure>\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.<\/p>\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.<\/p>\n
Adrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.<\/p>\n
While some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.<\/p>\n
\n\n\n9.6 Summary<\/span><\/h1>\n<\/header>\n\n\n- The adrenal glands<\/a>\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the adrenal cortex<\/a> and an inner layer called the adrenal medulla<\/a>.<\/li>\n
- The adrenal cortex produces steroid hormones called by the general term corticosteroids<\/a>, of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and androgens<\/a>\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\n
- The adrenal medulla produces non-steroid catecholamine hormones, including adrenaline<\/a> and noradrenaline<\/a>. These hormones stimulate the fight-or-flight response<\/a>.<\/li>\n
- Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include Cushing\u2019s syndrome<\/a>, in which there is hypersecretion of cortisol, and Addison\u2019s disease<\/a>, in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n9.6 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the structure and location of the adrenal glands.<\/li>\n
- \n\n
Adrenal Cortex<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"5867\"]adrenal cortex[\/pb_glossary],<\/strong> or outer layer of the adrenal gland, is divided into three additional layers, called zones (see Figure 9.6.3). Each zone has distinct enzymes that produce different hormones from the common precursor molecule cholesterol, which is a lipid.\r\n\r\n \t- [pb_glossary id=\"3480\"]Zona glomerulosa[\/pb_glossary]<\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\r\n \t
- [pb_glossary id=\"3481\"]Zona fasciculata[\/pb_glossary]<\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\r\n \t
- [pb_glossary id=\"3482\"]Zona reticularis[\/pb_glossary]<\/strong>\u00a0is the innermost layer of the adrenal cortex. It is directly adjacent to the medulla of the adrenal gland.<\/li>\r\n<\/ol>\r\n[caption id=\"attachment_3479\" align=\"aligncenter\" width=\"778\"] Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em>[\/caption]\r\n\r\n \r\n\r\n\r\nTypes of Adrenal Cortex Hormones<\/span>\r\n\r\n<\/div>\r\nHormones produced by the adrenal cortex are\u00a0known\u00a0by the general term\u00a0[pb_glossary id=\"5957\"]corticosteroids[\/pb_glossary].<\/strong> As [pb_glossary id=\"3423\"]steroid hormones[\/pb_glossary], corticosteroids are endocrine hormones that are made of [pb_glossary id=\"5651\"]lipids[\/pb_glossary] and exert their effects on [pb_glossary id=\"3422\"]target cells[\/pb_glossary] by crossing the [pb_glossary id=\"5489\"]plasma membrane[\/pb_glossary] and binding with receptors within the cytoplasm. A steroid hormone and its receptor form a complex that enters the cell [pb_glossary id=\"5797\"]nucleus[\/pb_glossary] and affects [pb_glossary id=\"6031\"]gene expression[\/pb_glossary]. There are three types of corticosteroids synthesized and secreted by the adrenal cortex. Each type is produced by a different zone of the adrenal cortex, as shown in Figure 9.6.4.\r\n\r\n[caption id=\"attachment_3484\" align=\"alignnone\" width=\"1102\"] Figure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em>[\/caption]\r\n
Mineralocorticoids<\/h3>\r\nMineralocorticoids are produced in the [pb_glossary id=\"3480\"]zona glomerulosa[\/pb_glossary] and include the hormone [pb_glossary id=\"5881\"]aldosterone[\/pb_glossary]. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.\r\nGlucocorticoids<\/h3>\r\nGlucocorticoids are produced in the [pb_glossary id=\"3481\"]zona fasciculata[\/pb_glossary] and include the hormone\u00a0[pb_glossary id=\"5959\"]cortisol[\/pb_glossary],\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of [pb_glossary id=\"5813\"]proteins[\/pb_glossary], fats, and sugars. In general, they increase the level of [pb_glossary id=\"5451\"]glucose[\/pb_glossary] and [pb_glossary id=\"5657\"]fatty acids[\/pb_glossary] circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.\r\nAndrogens<\/h3>\r\n[pb_glossary id=\"3485\"]Androgens[\/pb_glossary]<\/strong>\u00a0are produced in the[pb_glossary id=\"3482\"] zona reticularis[\/pb_glossary] and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as [pb_glossary id=\"3409\"]testosterone[\/pb_glossary] in the male gonads ([pb_glossary id=\"3486\"]testes[\/pb_glossary]). In adult females, they are converted to female sex hormones called [pb_glossary id=\"5995\"]estrogens[\/pb_glossary]\u00a0in the female gonads ([pb_glossary id=\"3487\"]ovaries[\/pb_glossary]).\r\nRegulation of Adrenal Cortex Hormones<\/h2>\r\n[pb_glossary id=\"3423\"]Steroid hormone[\/pb_glossary] production by the three zones of the adrenal cortex is regulated by hormones secreted by the [pb_glossary id=\"5887\"]anterior[\/pb_glossary] lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide [pb_glossary id=\"2955\"]negative feedback[\/pb_glossary] to the [pb_glossary id=\"2937\"]hypothalamus[\/pb_glossary] and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.\r\n\r\n[caption id=\"attachment_3488\" align=\"aligncenter\" width=\"652\"] Figure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em>[\/caption]\r\n\r\n\r\nAdrenal Medulla<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary]<\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0[pb_glossary id=\"5929\"]catecholamines[\/pb_glossary]<\/strong>, and they include\u00a0[pb_glossary id=\"5875\"]adrenaline[\/pb_glossary]<\/strong>\u00a0(also called epinephrine) and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary] (also called norepinephrine). These water-soluble, [pb_glossary id=\"3425\"]non-steroid hormones[\/pb_glossary]\u00a0are made of [pb_glossary id=\"5707\"]amino acids[\/pb_glossary]. As non-steroid hormones, they cannot cross the [pb_glossary id=\"5489\"]plasma membrane[\/pb_glossary] of [pb_glossary id=\"3422\"]target cells[\/pb_glossary]. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.\r\n\r\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the [pb_glossary id=\"3015\"]sympathetic division[\/pb_glossary] of the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary].\r\n\r\nDisorders of the Adrenal Glands<\/h1>\r\n<\/div>\r\nDisorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.\r\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\r\nHypersecretion of the glucocorticoid hormone [pb_glossary id=\"5959\"]cortisol[\/pb_glossary] leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary].<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.\r\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\r\n[caption id=\"attachment_3494\" align=\"alignleft\" width=\"475\"] Figure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em>[\/caption]\r\n\r\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary].<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.\r\n\r\nFeature: My Human Body<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_3495\" align=\"aligncenter\" width=\"877\"] Figure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline \"junkie's\" day!\u00a0<\/em>[\/caption]\r\n\r\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.\r\n\r\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.\r\n\r\nAdrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.\r\n\r\nWhile some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.\r\n\r\n\r\n9.6 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5869\"]adrenal glands[\/pb_glossary]\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the [pb_glossary id=\"5867\"]adrenal cortex[\/pb_glossary] and an inner layer called the [pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary].<\/li>\r\n \t
- The adrenal cortex produces steroid hormones called by the general term [pb_glossary id=\"5957\"]corticosteroids[\/pb_glossary], of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and [pb_glossary id=\"3485\"]androgens[\/pb_glossary]\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\r\n \t
- The adrenal medulla produces non-steroid catecholamine hormones, including [pb_glossary id=\"5875\"]adrenaline[\/pb_glossary] and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary]. These hormones stimulate the [pb_glossary id=\"6013\"]fight-or-flight response[\/pb_glossary].<\/li>\r\n \t
- Disorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include [pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary], in which there is hypersecretion of cortisol, and [pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary], in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the structure and location of the adrenal glands.<\/li>\r\n \t
- [h5p id=\"577\"]<\/li>\r\n \t
- Compare and contrast the adrenal cortex and adrenal medulla.<\/li>\r\n \t
- Identify the three layers of the adrenal cortex and the type of hormones each layer produces.<\/li>\r\n \t
- Give an example of each type of corticosteroid and state its function.<\/li>\r\n \t
- Explain how the production of glucocorticoids is regulated.<\/li>\r\n \t
- What is a catecholamine? Give an example of a catecholamine and state its function.<\/li>\r\n \t
- Compare and contrast Cushing\u2019s syndrome and Addison\u2019s disease.<\/li>\r\n \t
- What are two ways in which the nervous system (which includes the brain, spinal cord, and nerves) controls the adrenal gland?<\/li>\r\n \t
- Explain why a pituitary tumor can cause either hypersecretion or hyposecretion of cortisol.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU\r\nHow stress affects your body - Sharon Horesh Bergquist, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=WuyPuH9ojCE&feature=emb_logo\r\n
How stress affects your brain - Madhumita Murgia, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=emb_logo\r\n
Adrenaline: Fight or Flight Response, Henk van 't Klooster, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 9.6.1<\/strong>\r\n\r\nAttack from wikimedia commons<\/a> by Jerry Kirkhart<\/a> from Los Osos, Calif. on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 9.6.2<\/strong>\r\n\r\nDiagram_showing_where_the_adrenal_glands_are_in_the_body_CRUK_415.svg<\/a> by Cancer Research UK uploader<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 9.6.3<\/strong>\r\n\r\nAdrenal_cortex_labelled<\/a> by Jpogi<\/a>\u00a0at\u00a0English Wikipedia<\/a> on Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en) license.\r\n\r\nFigure 9.6.4<\/strong>\r\n\r\nThe_Adrenal_Glands<\/a> by OpenStax College<\/a> is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.5<\/strong>\r\n\r\nACTH negative feedback loop by Christinelmiller is used under a\u00a0CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.6<\/strong>\r\n\r\nA_69-Year-Old_Female_with_Tiredness_and_a_Persistent_Tan_01<\/a>\u00a0by Petros Perros<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.5\/deed.en) license.\r\n\r\nFigure 9.6.7<\/strong>\r\n\r\nBASE_Jumping_from_Sapphire_Tower_in_Istanbul<\/a> by Kontizas Dimitrios on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/3.0) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 17.17 Adrenal glands [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 17.6). OpenStax College. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/17-6-the-adrenal-glands<\/p>\r\nHenk van 't Klooster. (2013). Adrenaline: Fight or flight response. YouTube. https:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=youtu.be<\/p>\r\n
Perros, P. (2005). A 69-year-old female with tiredness and a persistent tan. PLoS Medicine,<\/em> 2(8): e229. https:\/\/doi.org\/10.1371\/journal.pmed.0020229<\/p>\r\nTED-Ed. (2015, October 22). How stress affects your body - Sharon Horesh Bergquist. YouTube. https:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, November 6). How stress affects your brain - Madhumita Murgia. YouTube. https:\/\/www.youtube.com\/watch?v=WuyPuH9ojCE&feature=youtu.be<\/p>\r\n \r\n\r\n ","rendered":"
<\/p>\nFigure 9.6.1 Got your nose!<\/em><\/figcaption><\/figure>\n\nEek!<\/h1>\n<\/div>\n
Being bitten on the nose by an eel certainly qualifies as a frightening experience! The fear this man is experiencing produces the same physiological responses in most people\u00a0\u2014\u00a0racing heart, rapid breathing, clammy hands. These and other fight-or-flight responses<\/a>\u00a0prepare the body to either defend itself or run away from danger. Why does fear elicit these changes in the body? The responses occur in large part because of hormones secreted by the adrenal glands.<\/p>\n\nIntroduction to the Adrenal Glands<\/h1>\n<\/div>\nFigure 9.6.2 Each of the two adrenal glands is found above a kidney.<\/em><\/figcaption><\/figure>\nThe\u00a0adrenal glands<\/a><\/strong> are endocrine glands that produce a variety of hormones. Adrenal hormones include the fight-or-flight hormone adrenaline and the steroid hormone cortisol. The two adrenal glands are located on both sides of the body, just above the kidneys, as shown in Figure 9.6.2. The right adrenal gland (on the left in the figure) is smaller and has a pyramidal shape. The left adrenal gland (on the right in the figure) is larger and has a half-moon shape.<\/p>\nEach adrenal gland has two distinct parts, and each part has a different function, although both parts produce hormones. There is an outer layer, called the adrenal cortex, which produces steroid hormones including cortisol. There is also an inner layer, called the adrenal medulla, which produces non-steroid hormones including adrenaline.<\/p>\n
\nAdrenal Cortex<\/h1>\n<\/div>\n
The\u00a0adrenal cortex<\/a>,<\/strong> or outer layer of the adrenal gland, is divided into three additional layers, called zones (see Figure 9.6.3). Each zone has distinct enzymes that produce different hormones from the common precursor molecule cholesterol, which is a lipid.<\/p>\n\n- Zona glomerulosa<\/a><\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\n
- Zona fasciculata<\/a><\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\n
- Zona reticularis<\/a><\/strong>\u00a0is the innermost layer of the adrenal cortex. It is directly adjacent to the medulla of the adrenal gland.<\/li>\n<\/ol>\n
Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em><\/figcaption><\/figure>\n <\/p>\n
\nTypes of Adrenal Cortex Hormones<\/span><\/p>\n<\/div>\nHormones produced by the adrenal cortex are\u00a0known\u00a0by the general term\u00a0corticosteroids<\/a>.<\/strong> As steroid hormones<\/a>, corticosteroids are endocrine hormones that are made of lipids<\/a> and exert their effects on target cells<\/a> by crossing the plasma membrane<\/a> and binding with receptors within the cytoplasm. A steroid hormone and its receptor form a complex that enters the cell nucleus<\/a> and affects gene expression<\/a>. There are three types of corticosteroids synthesized and secreted by the adrenal cortex. Each type is produced by a different zone of the adrenal cortex, as shown in Figure 9.6.4.<\/p>\nFigure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em><\/figcaption><\/figure>\nMineralocorticoids<\/h3>\n
Mineralocorticoids are produced in the zona glomerulosa<\/a> and include the hormone aldosterone<\/a>. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.<\/p>\nGlucocorticoids<\/h3>\n
Glucocorticoids are produced in the zona fasciculata<\/a> and include the hormone\u00a0cortisol<\/a>,\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of proteins<\/a>, fats, and sugars. In general, they increase the level of glucose<\/a> and fatty acids<\/a> circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.<\/p>\nAndrogens<\/h3>\n
Androgens<\/a><\/strong>\u00a0are produced in the zona reticularis<\/a> and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as testosterone<\/a> in the male gonads (testes<\/a>). In adult females, they are converted to female sex hormones called estrogens<\/a>\u00a0in the female gonads (ovaries<\/a>).<\/p>\nRegulation of Adrenal Cortex Hormones<\/h2>\n
Steroid hormone<\/a> production by the three zones of the adrenal cortex is regulated by hormones secreted by the anterior<\/a> lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide negative feedback<\/a> to the hypothalamus<\/a> and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.<\/p>\nFigure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em><\/figcaption><\/figure>\n\nAdrenal Medulla<\/h1>\n<\/div>\n
The\u00a0adrenal medulla<\/a><\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0catecholamines<\/a><\/strong>, and they include\u00a0adrenaline<\/a><\/strong>\u00a0(also called epinephrine) and noradrenaline<\/a> (also called norepinephrine). These water-soluble, non-steroid hormones<\/a>\u00a0are made of amino acids<\/a>. As non-steroid hormones, they cannot cross the plasma membrane<\/a> of target cells<\/a>. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.<\/p>\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the sympathetic division<\/a> of the autonomic nervous system<\/a>.<\/p>\n\nDisorders of the Adrenal Glands<\/h1>\n<\/div>\n
Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.<\/p>\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\n
Hypersecretion of the glucocorticoid hormone cortisol<\/a> leads to a disorder\u00a0called\u00a0Cushing\u2019s syndrome<\/a>.<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.<\/p>\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\nFigure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em><\/figcaption><\/figure>\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0Addison\u2019s disease<\/a>.<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.<\/p>\n\nFeature: My Human Body<\/h1>\n<\/div>\nFigure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline “junkie’s” day!\u00a0<\/em><\/figcaption><\/figure>\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.<\/p>\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.<\/p>\n
Adrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.<\/p>\n
While some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.<\/p>\n
\n\n\n9.6 Summary<\/span><\/h1>\n<\/header>\n\n\n- The adrenal glands<\/a>\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the adrenal cortex<\/a> and an inner layer called the adrenal medulla<\/a>.<\/li>\n
- The adrenal cortex produces steroid hormones called by the general term corticosteroids<\/a>, of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and androgens<\/a>\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\n
- The adrenal medulla produces non-steroid catecholamine hormones, including adrenaline<\/a> and noradrenaline<\/a>. These hormones stimulate the fight-or-flight response<\/a>.<\/li>\n
- Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include Cushing\u2019s syndrome<\/a>, in which there is hypersecretion of cortisol, and Addison\u2019s disease<\/a>, in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n9.6 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the structure and location of the adrenal glands.<\/li>\n
- \n\n
Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em>[\/caption]\r\n\r\n \r\n Figure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em>[\/caption]\r\nMineralocorticoids<\/h3>\r\nMineralocorticoids are produced in the [pb_glossary id=\"3480\"]zona glomerulosa[\/pb_glossary] and include the hormone [pb_glossary id=\"5881\"]aldosterone[\/pb_glossary]. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.\r\nGlucocorticoids<\/h3>\r\nGlucocorticoids are produced in the [pb_glossary id=\"3481\"]zona fasciculata[\/pb_glossary] and include the hormone\u00a0[pb_glossary id=\"5959\"]cortisol[\/pb_glossary],\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of [pb_glossary id=\"5813\"]proteins[\/pb_glossary], fats, and sugars. In general, they increase the level of [pb_glossary id=\"5451\"]glucose[\/pb_glossary] and [pb_glossary id=\"5657\"]fatty acids[\/pb_glossary] circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.\r\nAndrogens<\/h3>\r\n[pb_glossary id=\"3485\"]Androgens[\/pb_glossary]<\/strong>\u00a0are produced in the[pb_glossary id=\"3482\"] zona reticularis[\/pb_glossary] and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as [pb_glossary id=\"3409\"]testosterone[\/pb_glossary] in the male gonads ([pb_glossary id=\"3486\"]testes[\/pb_glossary]). In adult females, they are converted to female sex hormones called [pb_glossary id=\"5995\"]estrogens[\/pb_glossary]\u00a0in the female gonads ([pb_glossary id=\"3487\"]ovaries[\/pb_glossary]).\r\nRegulation of Adrenal Cortex Hormones<\/h2>\r\n[pb_glossary id=\"3423\"]Steroid hormone[\/pb_glossary] production by the three zones of the adrenal cortex is regulated by hormones secreted by the [pb_glossary id=\"5887\"]anterior[\/pb_glossary] lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide [pb_glossary id=\"2955\"]negative feedback[\/pb_glossary] to the [pb_glossary id=\"2937\"]hypothalamus[\/pb_glossary] and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.\r\n\r\n[caption id=\"attachment_3488\" align=\"aligncenter\" width=\"652\"] Figure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em>[\/caption]\r\n\r\n\r\nAdrenal Medulla<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary]<\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0[pb_glossary id=\"5929\"]catecholamines[\/pb_glossary]<\/strong>, and they include\u00a0[pb_glossary id=\"5875\"]adrenaline[\/pb_glossary]<\/strong>\u00a0(also called epinephrine) and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary] (also called norepinephrine). These water-soluble, [pb_glossary id=\"3425\"]non-steroid hormones[\/pb_glossary]\u00a0are made of [pb_glossary id=\"5707\"]amino acids[\/pb_glossary]. As non-steroid hormones, they cannot cross the [pb_glossary id=\"5489\"]plasma membrane[\/pb_glossary] of [pb_glossary id=\"3422\"]target cells[\/pb_glossary]. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.\r\n\r\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the [pb_glossary id=\"3015\"]sympathetic division[\/pb_glossary] of the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary].\r\n\r\nDisorders of the Adrenal Glands<\/h1>\r\n<\/div>\r\nDisorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.\r\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\r\nHypersecretion of the glucocorticoid hormone [pb_glossary id=\"5959\"]cortisol[\/pb_glossary] leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary].<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.\r\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\r\n[caption id=\"attachment_3494\" align=\"alignleft\" width=\"475\"] Figure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em>[\/caption]\r\n\r\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary].<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.\r\n\r\nFeature: My Human Body<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_3495\" align=\"aligncenter\" width=\"877\"] Figure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline \"junkie's\" day!\u00a0<\/em>[\/caption]\r\n\r\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.\r\n\r\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.\r\n\r\nAdrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.\r\n\r\nWhile some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.\r\n\r\n\r\n9.6 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5869\"]adrenal glands[\/pb_glossary]\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the [pb_glossary id=\"5867\"]adrenal cortex[\/pb_glossary] and an inner layer called the [pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary].<\/li>\r\n \t
- The adrenal cortex produces steroid hormones called by the general term [pb_glossary id=\"5957\"]corticosteroids[\/pb_glossary], of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and [pb_glossary id=\"3485\"]androgens[\/pb_glossary]\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\r\n \t
- The adrenal medulla produces non-steroid catecholamine hormones, including [pb_glossary id=\"5875\"]adrenaline[\/pb_glossary] and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary]. These hormones stimulate the [pb_glossary id=\"6013\"]fight-or-flight response[\/pb_glossary].<\/li>\r\n \t
- Disorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include [pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary], in which there is hypersecretion of cortisol, and [pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary], in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the structure and location of the adrenal glands.<\/li>\r\n \t
- [h5p id=\"577\"]<\/li>\r\n \t
- Compare and contrast the adrenal cortex and adrenal medulla.<\/li>\r\n \t
- Identify the three layers of the adrenal cortex and the type of hormones each layer produces.<\/li>\r\n \t
- Give an example of each type of corticosteroid and state its function.<\/li>\r\n \t
- Explain how the production of glucocorticoids is regulated.<\/li>\r\n \t
- What is a catecholamine? Give an example of a catecholamine and state its function.<\/li>\r\n \t
- Compare and contrast Cushing\u2019s syndrome and Addison\u2019s disease.<\/li>\r\n \t
- What are two ways in which the nervous system (which includes the brain, spinal cord, and nerves) controls the adrenal gland?<\/li>\r\n \t
- Explain why a pituitary tumor can cause either hypersecretion or hyposecretion of cortisol.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU\r\nHow stress affects your body - Sharon Horesh Bergquist, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=WuyPuH9ojCE&feature=emb_logo\r\n
How stress affects your brain - Madhumita Murgia, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=emb_logo\r\n
Adrenaline: Fight or Flight Response, Henk van 't Klooster, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 9.6.1<\/strong>\r\n\r\nAttack from wikimedia commons<\/a> by Jerry Kirkhart<\/a> from Los Osos, Calif. on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 9.6.2<\/strong>\r\n\r\nDiagram_showing_where_the_adrenal_glands_are_in_the_body_CRUK_415.svg<\/a> by Cancer Research UK uploader<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 9.6.3<\/strong>\r\n\r\nAdrenal_cortex_labelled<\/a> by Jpogi<\/a>\u00a0at\u00a0English Wikipedia<\/a> on Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en) license.\r\n\r\nFigure 9.6.4<\/strong>\r\n\r\nThe_Adrenal_Glands<\/a> by OpenStax College<\/a> is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.5<\/strong>\r\n\r\nACTH negative feedback loop by Christinelmiller is used under a\u00a0CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.6<\/strong>\r\n\r\nA_69-Year-Old_Female_with_Tiredness_and_a_Persistent_Tan_01<\/a>\u00a0by Petros Perros<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.5\/deed.en) license.\r\n\r\nFigure 9.6.7<\/strong>\r\n\r\nBASE_Jumping_from_Sapphire_Tower_in_Istanbul<\/a> by Kontizas Dimitrios on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/3.0) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 17.17 Adrenal glands [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 17.6). OpenStax College. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/17-6-the-adrenal-glands<\/p>\r\nHenk van 't Klooster. (2013). Adrenaline: Fight or flight response. YouTube. https:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=youtu.be<\/p>\r\n
Perros, P. (2005). A 69-year-old female with tiredness and a persistent tan. PLoS Medicine,<\/em> 2(8): e229. https:\/\/doi.org\/10.1371\/journal.pmed.0020229<\/p>\r\nTED-Ed. (2015, October 22). How stress affects your body - Sharon Horesh Bergquist. YouTube. https:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, November 6). How stress affects your brain - Madhumita Murgia. YouTube. https:\/\/www.youtube.com\/watch?v=WuyPuH9ojCE&feature=youtu.be<\/p>\r\n \r\n\r\n ","rendered":"
<\/p>\nFigure 9.6.1 Got your nose!<\/em><\/figcaption><\/figure>\n\nEek!<\/h1>\n<\/div>\n
Being bitten on the nose by an eel certainly qualifies as a frightening experience! The fear this man is experiencing produces the same physiological responses in most people\u00a0\u2014\u00a0racing heart, rapid breathing, clammy hands. These and other fight-or-flight responses<\/a>\u00a0prepare the body to either defend itself or run away from danger. Why does fear elicit these changes in the body? The responses occur in large part because of hormones secreted by the adrenal glands.<\/p>\n\nIntroduction to the Adrenal Glands<\/h1>\n<\/div>\nFigure 9.6.2 Each of the two adrenal glands is found above a kidney.<\/em><\/figcaption><\/figure>\nThe\u00a0adrenal glands<\/a><\/strong> are endocrine glands that produce a variety of hormones. Adrenal hormones include the fight-or-flight hormone adrenaline and the steroid hormone cortisol. The two adrenal glands are located on both sides of the body, just above the kidneys, as shown in Figure 9.6.2. The right adrenal gland (on the left in the figure) is smaller and has a pyramidal shape. The left adrenal gland (on the right in the figure) is larger and has a half-moon shape.<\/p>\nEach adrenal gland has two distinct parts, and each part has a different function, although both parts produce hormones. There is an outer layer, called the adrenal cortex, which produces steroid hormones including cortisol. There is also an inner layer, called the adrenal medulla, which produces non-steroid hormones including adrenaline.<\/p>\n
\nAdrenal Cortex<\/h1>\n<\/div>\n
The\u00a0adrenal cortex<\/a>,<\/strong> or outer layer of the adrenal gland, is divided into three additional layers, called zones (see Figure 9.6.3). Each zone has distinct enzymes that produce different hormones from the common precursor molecule cholesterol, which is a lipid.<\/p>\n\n- Zona glomerulosa<\/a><\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\n
- Zona fasciculata<\/a><\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\n
- Zona reticularis<\/a><\/strong>\u00a0is the innermost layer of the adrenal cortex. It is directly adjacent to the medulla of the adrenal gland.<\/li>\n<\/ol>\n
Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em><\/figcaption><\/figure>\n <\/p>\n
\nTypes of Adrenal Cortex Hormones<\/span><\/p>\n<\/div>\nHormones produced by the adrenal cortex are\u00a0known\u00a0by the general term\u00a0corticosteroids<\/a>.<\/strong> As steroid hormones<\/a>, corticosteroids are endocrine hormones that are made of lipids<\/a> and exert their effects on target cells<\/a> by crossing the plasma membrane<\/a> and binding with receptors within the cytoplasm. A steroid hormone and its receptor form a complex that enters the cell nucleus<\/a> and affects gene expression<\/a>. There are three types of corticosteroids synthesized and secreted by the adrenal cortex. Each type is produced by a different zone of the adrenal cortex, as shown in Figure 9.6.4.<\/p>\nFigure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em><\/figcaption><\/figure>\nMineralocorticoids<\/h3>\n
Mineralocorticoids are produced in the zona glomerulosa<\/a> and include the hormone aldosterone<\/a>. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.<\/p>\nGlucocorticoids<\/h3>\n
Glucocorticoids are produced in the zona fasciculata<\/a> and include the hormone\u00a0cortisol<\/a>,\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of proteins<\/a>, fats, and sugars. In general, they increase the level of glucose<\/a> and fatty acids<\/a> circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.<\/p>\nAndrogens<\/h3>\n
Androgens<\/a><\/strong>\u00a0are produced in the zona reticularis<\/a> and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as testosterone<\/a> in the male gonads (testes<\/a>). In adult females, they are converted to female sex hormones called estrogens<\/a>\u00a0in the female gonads (ovaries<\/a>).<\/p>\nRegulation of Adrenal Cortex Hormones<\/h2>\n
Steroid hormone<\/a> production by the three zones of the adrenal cortex is regulated by hormones secreted by the anterior<\/a> lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide negative feedback<\/a> to the hypothalamus<\/a> and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.<\/p>\nFigure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em><\/figcaption><\/figure>\n\nAdrenal Medulla<\/h1>\n<\/div>\n
The\u00a0adrenal medulla<\/a><\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0catecholamines<\/a><\/strong>, and they include\u00a0adrenaline<\/a><\/strong>\u00a0(also called epinephrine) and noradrenaline<\/a> (also called norepinephrine). These water-soluble, non-steroid hormones<\/a>\u00a0are made of amino acids<\/a>. As non-steroid hormones, they cannot cross the plasma membrane<\/a> of target cells<\/a>. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.<\/p>\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the sympathetic division<\/a> of the autonomic nervous system<\/a>.<\/p>\n\nDisorders of the Adrenal Glands<\/h1>\n<\/div>\n
Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.<\/p>\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\n
Hypersecretion of the glucocorticoid hormone cortisol<\/a> leads to a disorder\u00a0called\u00a0Cushing\u2019s syndrome<\/a>.<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.<\/p>\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\nFigure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em><\/figcaption><\/figure>\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0Addison\u2019s disease<\/a>.<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.<\/p>\n\nFeature: My Human Body<\/h1>\n<\/div>\nFigure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline “junkie’s” day!\u00a0<\/em><\/figcaption><\/figure>\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.<\/p>\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.<\/p>\n
Adrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.<\/p>\n
While some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.<\/p>\n
\n\n\n9.6 Summary<\/span><\/h1>\n<\/header>\n\n\n- The adrenal glands<\/a>\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the adrenal cortex<\/a> and an inner layer called the adrenal medulla<\/a>.<\/li>\n
- The adrenal cortex produces steroid hormones called by the general term corticosteroids<\/a>, of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and androgens<\/a>\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\n
- The adrenal medulla produces non-steroid catecholamine hormones, including adrenaline<\/a> and noradrenaline<\/a>. These hormones stimulate the fight-or-flight response<\/a>.<\/li>\n
- Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include Cushing\u2019s syndrome<\/a>, in which there is hypersecretion of cortisol, and Addison\u2019s disease<\/a>, in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n9.6 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the structure and location of the adrenal glands.<\/li>\n
- \n\n
Androgens<\/h3>\r\n[pb_glossary id=\"3485\"]Androgens[\/pb_glossary]<\/strong>\u00a0are produced in the[pb_glossary id=\"3482\"] zona reticularis[\/pb_glossary] and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as [pb_glossary id=\"3409\"]testosterone[\/pb_glossary] in the male gonads ([pb_glossary id=\"3486\"]testes[\/pb_glossary]). In adult females, they are converted to female sex hormones called [pb_glossary id=\"5995\"]estrogens[\/pb_glossary]\u00a0in the female gonads ([pb_glossary id=\"3487\"]ovaries[\/pb_glossary]).\r\nRegulation of Adrenal Cortex Hormones<\/h2>\r\n[pb_glossary id=\"3423\"]Steroid hormone[\/pb_glossary] production by the three zones of the adrenal cortex is regulated by hormones secreted by the [pb_glossary id=\"5887\"]anterior[\/pb_glossary] lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide [pb_glossary id=\"2955\"]negative feedback[\/pb_glossary] to the [pb_glossary id=\"2937\"]hypothalamus[\/pb_glossary] and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.\r\n\r\n[caption id=\"attachment_3488\" align=\"aligncenter\" width=\"652\"] Figure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em>[\/caption]\r\n\r\n\r\nAdrenal Medulla<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary]<\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0[pb_glossary id=\"5929\"]catecholamines[\/pb_glossary]<\/strong>, and they include\u00a0[pb_glossary id=\"5875\"]adrenaline[\/pb_glossary]<\/strong>\u00a0(also called epinephrine) and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary] (also called norepinephrine). These water-soluble, [pb_glossary id=\"3425\"]non-steroid hormones[\/pb_glossary]\u00a0are made of [pb_glossary id=\"5707\"]amino acids[\/pb_glossary]. As non-steroid hormones, they cannot cross the [pb_glossary id=\"5489\"]plasma membrane[\/pb_glossary] of [pb_glossary id=\"3422\"]target cells[\/pb_glossary]. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.\r\n\r\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the [pb_glossary id=\"3015\"]sympathetic division[\/pb_glossary] of the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary].\r\n\r\nDisorders of the Adrenal Glands<\/h1>\r\n<\/div>\r\nDisorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.\r\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\r\nHypersecretion of the glucocorticoid hormone [pb_glossary id=\"5959\"]cortisol[\/pb_glossary] leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary].<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.\r\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\r\n[caption id=\"attachment_3494\" align=\"alignleft\" width=\"475\"] Figure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em>[\/caption]\r\n\r\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary].<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.\r\n\r\nFeature: My Human Body<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_3495\" align=\"aligncenter\" width=\"877\"] Figure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline \"junkie's\" day!\u00a0<\/em>[\/caption]\r\n\r\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.\r\n\r\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.\r\n\r\nAdrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.\r\n\r\nWhile some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.\r\n\r\n\r\n9.6 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5869\"]adrenal glands[\/pb_glossary]\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the [pb_glossary id=\"5867\"]adrenal cortex[\/pb_glossary] and an inner layer called the [pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary].<\/li>\r\n \t
- The adrenal cortex produces steroid hormones called by the general term [pb_glossary id=\"5957\"]corticosteroids[\/pb_glossary], of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and [pb_glossary id=\"3485\"]androgens[\/pb_glossary]\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\r\n \t
- The adrenal medulla produces non-steroid catecholamine hormones, including [pb_glossary id=\"5875\"]adrenaline[\/pb_glossary] and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary]. These hormones stimulate the [pb_glossary id=\"6013\"]fight-or-flight response[\/pb_glossary].<\/li>\r\n \t
- Disorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include [pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary], in which there is hypersecretion of cortisol, and [pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary], in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the structure and location of the adrenal glands.<\/li>\r\n \t
- [h5p id=\"577\"]<\/li>\r\n \t
- Compare and contrast the adrenal cortex and adrenal medulla.<\/li>\r\n \t
- Identify the three layers of the adrenal cortex and the type of hormones each layer produces.<\/li>\r\n \t
- Give an example of each type of corticosteroid and state its function.<\/li>\r\n \t
- Explain how the production of glucocorticoids is regulated.<\/li>\r\n \t
- What is a catecholamine? Give an example of a catecholamine and state its function.<\/li>\r\n \t
- Compare and contrast Cushing\u2019s syndrome and Addison\u2019s disease.<\/li>\r\n \t
- What are two ways in which the nervous system (which includes the brain, spinal cord, and nerves) controls the adrenal gland?<\/li>\r\n \t
- Explain why a pituitary tumor can cause either hypersecretion or hyposecretion of cortisol.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU\r\nHow stress affects your body - Sharon Horesh Bergquist, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=WuyPuH9ojCE&feature=emb_logo\r\n
How stress affects your brain - Madhumita Murgia, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=emb_logo\r\n
Adrenaline: Fight or Flight Response, Henk van 't Klooster, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 9.6.1<\/strong>\r\n\r\nAttack from wikimedia commons<\/a> by Jerry Kirkhart<\/a> from Los Osos, Calif. on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 9.6.2<\/strong>\r\n\r\nDiagram_showing_where_the_adrenal_glands_are_in_the_body_CRUK_415.svg<\/a> by Cancer Research UK uploader<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 9.6.3<\/strong>\r\n\r\nAdrenal_cortex_labelled<\/a> by Jpogi<\/a>\u00a0at\u00a0English Wikipedia<\/a> on Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en) license.\r\n\r\nFigure 9.6.4<\/strong>\r\n\r\nThe_Adrenal_Glands<\/a> by OpenStax College<\/a> is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.5<\/strong>\r\n\r\nACTH negative feedback loop by Christinelmiller is used under a\u00a0CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.6<\/strong>\r\n\r\nA_69-Year-Old_Female_with_Tiredness_and_a_Persistent_Tan_01<\/a>\u00a0by Petros Perros<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.5\/deed.en) license.\r\n\r\nFigure 9.6.7<\/strong>\r\n\r\nBASE_Jumping_from_Sapphire_Tower_in_Istanbul<\/a> by Kontizas Dimitrios on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/3.0) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 17.17 Adrenal glands [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 17.6). OpenStax College. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/17-6-the-adrenal-glands<\/p>\r\nHenk van 't Klooster. (2013). Adrenaline: Fight or flight response. YouTube. https:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=youtu.be<\/p>\r\n
Perros, P. (2005). A 69-year-old female with tiredness and a persistent tan. PLoS Medicine,<\/em> 2(8): e229. https:\/\/doi.org\/10.1371\/journal.pmed.0020229<\/p>\r\nTED-Ed. (2015, October 22). How stress affects your body - Sharon Horesh Bergquist. YouTube. https:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, November 6). How stress affects your brain - Madhumita Murgia. YouTube. https:\/\/www.youtube.com\/watch?v=WuyPuH9ojCE&feature=youtu.be<\/p>\r\n \r\n\r\n ","rendered":"
<\/p>\nFigure 9.6.1 Got your nose!<\/em><\/figcaption><\/figure>\n\nEek!<\/h1>\n<\/div>\n
Being bitten on the nose by an eel certainly qualifies as a frightening experience! The fear this man is experiencing produces the same physiological responses in most people\u00a0\u2014\u00a0racing heart, rapid breathing, clammy hands. These and other fight-or-flight responses<\/a>\u00a0prepare the body to either defend itself or run away from danger. Why does fear elicit these changes in the body? The responses occur in large part because of hormones secreted by the adrenal glands.<\/p>\n\nIntroduction to the Adrenal Glands<\/h1>\n<\/div>\nFigure 9.6.2 Each of the two adrenal glands is found above a kidney.<\/em><\/figcaption><\/figure>\nThe\u00a0adrenal glands<\/a><\/strong> are endocrine glands that produce a variety of hormones. Adrenal hormones include the fight-or-flight hormone adrenaline and the steroid hormone cortisol. The two adrenal glands are located on both sides of the body, just above the kidneys, as shown in Figure 9.6.2. The right adrenal gland (on the left in the figure) is smaller and has a pyramidal shape. The left adrenal gland (on the right in the figure) is larger and has a half-moon shape.<\/p>\nEach adrenal gland has two distinct parts, and each part has a different function, although both parts produce hormones. There is an outer layer, called the adrenal cortex, which produces steroid hormones including cortisol. There is also an inner layer, called the adrenal medulla, which produces non-steroid hormones including adrenaline.<\/p>\n
\nAdrenal Cortex<\/h1>\n<\/div>\n
The\u00a0adrenal cortex<\/a>,<\/strong> or outer layer of the adrenal gland, is divided into three additional layers, called zones (see Figure 9.6.3). Each zone has distinct enzymes that produce different hormones from the common precursor molecule cholesterol, which is a lipid.<\/p>\n\n- Zona glomerulosa<\/a><\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\n
- Zona fasciculata<\/a><\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\n
- Zona reticularis<\/a><\/strong>\u00a0is the innermost layer of the adrenal cortex. It is directly adjacent to the medulla of the adrenal gland.<\/li>\n<\/ol>\n
Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em><\/figcaption><\/figure>\n <\/p>\n
\nTypes of Adrenal Cortex Hormones<\/span><\/p>\n<\/div>\nHormones produced by the adrenal cortex are\u00a0known\u00a0by the general term\u00a0corticosteroids<\/a>.<\/strong> As steroid hormones<\/a>, corticosteroids are endocrine hormones that are made of lipids<\/a> and exert their effects on target cells<\/a> by crossing the plasma membrane<\/a> and binding with receptors within the cytoplasm. A steroid hormone and its receptor form a complex that enters the cell nucleus<\/a> and affects gene expression<\/a>. There are three types of corticosteroids synthesized and secreted by the adrenal cortex. Each type is produced by a different zone of the adrenal cortex, as shown in Figure 9.6.4.<\/p>\nFigure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em><\/figcaption><\/figure>\nMineralocorticoids<\/h3>\n
Mineralocorticoids are produced in the zona glomerulosa<\/a> and include the hormone aldosterone<\/a>. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.<\/p>\nGlucocorticoids<\/h3>\n
Glucocorticoids are produced in the zona fasciculata<\/a> and include the hormone\u00a0cortisol<\/a>,\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of proteins<\/a>, fats, and sugars. In general, they increase the level of glucose<\/a> and fatty acids<\/a> circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.<\/p>\nAndrogens<\/h3>\n
Androgens<\/a><\/strong>\u00a0are produced in the zona reticularis<\/a> and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as testosterone<\/a> in the male gonads (testes<\/a>). In adult females, they are converted to female sex hormones called estrogens<\/a>\u00a0in the female gonads (ovaries<\/a>).<\/p>\nRegulation of Adrenal Cortex Hormones<\/h2>\n
Steroid hormone<\/a> production by the three zones of the adrenal cortex is regulated by hormones secreted by the anterior<\/a> lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide negative feedback<\/a> to the hypothalamus<\/a> and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.<\/p>\nFigure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em><\/figcaption><\/figure>\n\nAdrenal Medulla<\/h1>\n<\/div>\n
The\u00a0adrenal medulla<\/a><\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0catecholamines<\/a><\/strong>, and they include\u00a0adrenaline<\/a><\/strong>\u00a0(also called epinephrine) and noradrenaline<\/a> (also called norepinephrine). These water-soluble, non-steroid hormones<\/a>\u00a0are made of amino acids<\/a>. As non-steroid hormones, they cannot cross the plasma membrane<\/a> of target cells<\/a>. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.<\/p>\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the sympathetic division<\/a> of the autonomic nervous system<\/a>.<\/p>\n\nDisorders of the Adrenal Glands<\/h1>\n<\/div>\n
Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.<\/p>\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\n
Hypersecretion of the glucocorticoid hormone cortisol<\/a> leads to a disorder\u00a0called\u00a0Cushing\u2019s syndrome<\/a>.<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.<\/p>\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\nFigure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em><\/figcaption><\/figure>\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0Addison\u2019s disease<\/a>.<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.<\/p>\n\nFeature: My Human Body<\/h1>\n<\/div>\nFigure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline “junkie’s” day!\u00a0<\/em><\/figcaption><\/figure>\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.<\/p>\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.<\/p>\n
Adrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.<\/p>\n
While some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.<\/p>\n
\n\n\n9.6 Summary<\/span><\/h1>\n<\/header>\n\n\n- The adrenal glands<\/a>\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the adrenal cortex<\/a> and an inner layer called the adrenal medulla<\/a>.<\/li>\n
- The adrenal cortex produces steroid hormones called by the general term corticosteroids<\/a>, of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and androgens<\/a>\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\n
- The adrenal medulla produces non-steroid catecholamine hormones, including adrenaline<\/a> and noradrenaline<\/a>. These hormones stimulate the fight-or-flight response<\/a>.<\/li>\n
- Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include Cushing\u2019s syndrome<\/a>, in which there is hypersecretion of cortisol, and Addison\u2019s disease<\/a>, in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n9.6 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the structure and location of the adrenal glands.<\/li>\n
- \n\n
Figure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em>[\/caption]\r\n\r\nAdrenal Medulla<\/h1>\r\n<\/div>\r\nThe\u00a0[pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary]<\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0[pb_glossary id=\"5929\"]catecholamines[\/pb_glossary]<\/strong>, and they include\u00a0[pb_glossary id=\"5875\"]adrenaline[\/pb_glossary]<\/strong>\u00a0(also called epinephrine) and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary] (also called norepinephrine). These water-soluble, [pb_glossary id=\"3425\"]non-steroid hormones[\/pb_glossary]\u00a0are made of [pb_glossary id=\"5707\"]amino acids[\/pb_glossary]. As non-steroid hormones, they cannot cross the [pb_glossary id=\"5489\"]plasma membrane[\/pb_glossary] of [pb_glossary id=\"3422\"]target cells[\/pb_glossary]. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.\r\n\r\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the [pb_glossary id=\"3015\"]sympathetic division[\/pb_glossary] of the [pb_glossary id=\"5899\"]autonomic nervous system[\/pb_glossary].\r\n\r\nDisorders of the Adrenal Glands<\/h1>\r\n<\/div>\r\nDisorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.\r\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\r\nHypersecretion of the glucocorticoid hormone [pb_glossary id=\"5959\"]cortisol[\/pb_glossary] leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary].<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.\r\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\r\n[caption id=\"attachment_3494\" align=\"alignleft\" width=\"475\"] Figure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em>[\/caption]\r\n\r\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary].<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.\r\n\r\nFeature: My Human Body<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_3495\" align=\"aligncenter\" width=\"877\"] Figure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline \"junkie's\" day!\u00a0<\/em>[\/caption]\r\n\r\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.\r\n\r\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.\r\n\r\nAdrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.\r\n\r\nWhile some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.\r\n\r\n\r\n9.6 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5869\"]adrenal glands[\/pb_glossary]\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the [pb_glossary id=\"5867\"]adrenal cortex[\/pb_glossary] and an inner layer called the [pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary].<\/li>\r\n \t
- The adrenal cortex produces steroid hormones called by the general term [pb_glossary id=\"5957\"]corticosteroids[\/pb_glossary], of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and [pb_glossary id=\"3485\"]androgens[\/pb_glossary]\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\r\n \t
- The adrenal medulla produces non-steroid catecholamine hormones, including [pb_glossary id=\"5875\"]adrenaline[\/pb_glossary] and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary]. These hormones stimulate the [pb_glossary id=\"6013\"]fight-or-flight response[\/pb_glossary].<\/li>\r\n \t
- Disorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include [pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary], in which there is hypersecretion of cortisol, and [pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary], in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the structure and location of the adrenal glands.<\/li>\r\n \t
- [h5p id=\"577\"]<\/li>\r\n \t
- Compare and contrast the adrenal cortex and adrenal medulla.<\/li>\r\n \t
- Identify the three layers of the adrenal cortex and the type of hormones each layer produces.<\/li>\r\n \t
- Give an example of each type of corticosteroid and state its function.<\/li>\r\n \t
- Explain how the production of glucocorticoids is regulated.<\/li>\r\n \t
- What is a catecholamine? Give an example of a catecholamine and state its function.<\/li>\r\n \t
- Compare and contrast Cushing\u2019s syndrome and Addison\u2019s disease.<\/li>\r\n \t
- What are two ways in which the nervous system (which includes the brain, spinal cord, and nerves) controls the adrenal gland?<\/li>\r\n \t
- Explain why a pituitary tumor can cause either hypersecretion or hyposecretion of cortisol.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU\r\nHow stress affects your body - Sharon Horesh Bergquist, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=WuyPuH9ojCE&feature=emb_logo\r\n
How stress affects your brain - Madhumita Murgia, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=emb_logo\r\n
Adrenaline: Fight or Flight Response, Henk van 't Klooster, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 9.6.1<\/strong>\r\n\r\nAttack from wikimedia commons<\/a> by Jerry Kirkhart<\/a> from Los Osos, Calif. on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 9.6.2<\/strong>\r\n\r\nDiagram_showing_where_the_adrenal_glands_are_in_the_body_CRUK_415.svg<\/a> by Cancer Research UK uploader<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 9.6.3<\/strong>\r\n\r\nAdrenal_cortex_labelled<\/a> by Jpogi<\/a>\u00a0at\u00a0English Wikipedia<\/a> on Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en) license.\r\n\r\nFigure 9.6.4<\/strong>\r\n\r\nThe_Adrenal_Glands<\/a> by OpenStax College<\/a> is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.5<\/strong>\r\n\r\nACTH negative feedback loop by Christinelmiller is used under a\u00a0CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.6<\/strong>\r\n\r\nA_69-Year-Old_Female_with_Tiredness_and_a_Persistent_Tan_01<\/a>\u00a0by Petros Perros<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.5\/deed.en) license.\r\n\r\nFigure 9.6.7<\/strong>\r\n\r\nBASE_Jumping_from_Sapphire_Tower_in_Istanbul<\/a> by Kontizas Dimitrios on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/3.0) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 17.17 Adrenal glands [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 17.6). OpenStax College. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/17-6-the-adrenal-glands<\/p>\r\nHenk van 't Klooster. (2013). Adrenaline: Fight or flight response. YouTube. https:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=youtu.be<\/p>\r\n
Perros, P. (2005). A 69-year-old female with tiredness and a persistent tan. PLoS Medicine,<\/em> 2(8): e229. https:\/\/doi.org\/10.1371\/journal.pmed.0020229<\/p>\r\nTED-Ed. (2015, October 22). How stress affects your body - Sharon Horesh Bergquist. YouTube. https:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, November 6). How stress affects your brain - Madhumita Murgia. YouTube. https:\/\/www.youtube.com\/watch?v=WuyPuH9ojCE&feature=youtu.be<\/p>\r\n \r\n\r\n ","rendered":"
<\/p>\nFigure 9.6.1 Got your nose!<\/em><\/figcaption><\/figure>\n\nEek!<\/h1>\n<\/div>\n
Being bitten on the nose by an eel certainly qualifies as a frightening experience! The fear this man is experiencing produces the same physiological responses in most people\u00a0\u2014\u00a0racing heart, rapid breathing, clammy hands. These and other fight-or-flight responses<\/a>\u00a0prepare the body to either defend itself or run away from danger. Why does fear elicit these changes in the body? The responses occur in large part because of hormones secreted by the adrenal glands.<\/p>\n\nIntroduction to the Adrenal Glands<\/h1>\n<\/div>\nFigure 9.6.2 Each of the two adrenal glands is found above a kidney.<\/em><\/figcaption><\/figure>\nThe\u00a0adrenal glands<\/a><\/strong> are endocrine glands that produce a variety of hormones. Adrenal hormones include the fight-or-flight hormone adrenaline and the steroid hormone cortisol. The two adrenal glands are located on both sides of the body, just above the kidneys, as shown in Figure 9.6.2. The right adrenal gland (on the left in the figure) is smaller and has a pyramidal shape. The left adrenal gland (on the right in the figure) is larger and has a half-moon shape.<\/p>\nEach adrenal gland has two distinct parts, and each part has a different function, although both parts produce hormones. There is an outer layer, called the adrenal cortex, which produces steroid hormones including cortisol. There is also an inner layer, called the adrenal medulla, which produces non-steroid hormones including adrenaline.<\/p>\n
\nAdrenal Cortex<\/h1>\n<\/div>\n
The\u00a0adrenal cortex<\/a>,<\/strong> or outer layer of the adrenal gland, is divided into three additional layers, called zones (see Figure 9.6.3). Each zone has distinct enzymes that produce different hormones from the common precursor molecule cholesterol, which is a lipid.<\/p>\n\n- Zona glomerulosa<\/a><\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\n
- Zona fasciculata<\/a><\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\n
- Zona reticularis<\/a><\/strong>\u00a0is the innermost layer of the adrenal cortex. It is directly adjacent to the medulla of the adrenal gland.<\/li>\n<\/ol>\n
Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em><\/figcaption><\/figure>\n <\/p>\n
\nTypes of Adrenal Cortex Hormones<\/span><\/p>\n<\/div>\nHormones produced by the adrenal cortex are\u00a0known\u00a0by the general term\u00a0corticosteroids<\/a>.<\/strong> As steroid hormones<\/a>, corticosteroids are endocrine hormones that are made of lipids<\/a> and exert their effects on target cells<\/a> by crossing the plasma membrane<\/a> and binding with receptors within the cytoplasm. A steroid hormone and its receptor form a complex that enters the cell nucleus<\/a> and affects gene expression<\/a>. There are three types of corticosteroids synthesized and secreted by the adrenal cortex. Each type is produced by a different zone of the adrenal cortex, as shown in Figure 9.6.4.<\/p>\nFigure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em><\/figcaption><\/figure>\nMineralocorticoids<\/h3>\n
Mineralocorticoids are produced in the zona glomerulosa<\/a> and include the hormone aldosterone<\/a>. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.<\/p>\nGlucocorticoids<\/h3>\n
Glucocorticoids are produced in the zona fasciculata<\/a> and include the hormone\u00a0cortisol<\/a>,\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of proteins<\/a>, fats, and sugars. In general, they increase the level of glucose<\/a> and fatty acids<\/a> circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.<\/p>\nAndrogens<\/h3>\n
Androgens<\/a><\/strong>\u00a0are produced in the zona reticularis<\/a> and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as testosterone<\/a> in the male gonads (testes<\/a>). In adult females, they are converted to female sex hormones called estrogens<\/a>\u00a0in the female gonads (ovaries<\/a>).<\/p>\nRegulation of Adrenal Cortex Hormones<\/h2>\n
Steroid hormone<\/a> production by the three zones of the adrenal cortex is regulated by hormones secreted by the anterior<\/a> lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide negative feedback<\/a> to the hypothalamus<\/a> and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.<\/p>\nFigure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em><\/figcaption><\/figure>\n\nAdrenal Medulla<\/h1>\n<\/div>\n
The\u00a0adrenal medulla<\/a><\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0catecholamines<\/a><\/strong>, and they include\u00a0adrenaline<\/a><\/strong>\u00a0(also called epinephrine) and noradrenaline<\/a> (also called norepinephrine). These water-soluble, non-steroid hormones<\/a>\u00a0are made of amino acids<\/a>. As non-steroid hormones, they cannot cross the plasma membrane<\/a> of target cells<\/a>. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.<\/p>\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the sympathetic division<\/a> of the autonomic nervous system<\/a>.<\/p>\n\nDisorders of the Adrenal Glands<\/h1>\n<\/div>\n
Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.<\/p>\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\n
Hypersecretion of the glucocorticoid hormone cortisol<\/a> leads to a disorder\u00a0called\u00a0Cushing\u2019s syndrome<\/a>.<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.<\/p>\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\nFigure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em><\/figcaption><\/figure>\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0Addison\u2019s disease<\/a>.<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.<\/p>\n\nFeature: My Human Body<\/h1>\n<\/div>\nFigure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline “junkie’s” day!\u00a0<\/em><\/figcaption><\/figure>\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.<\/p>\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.<\/p>\n
Adrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.<\/p>\n
While some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.<\/p>\n
\n\n\n9.6 Summary<\/span><\/h1>\n<\/header>\n\n\n- The adrenal glands<\/a>\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the adrenal cortex<\/a> and an inner layer called the adrenal medulla<\/a>.<\/li>\n
- The adrenal cortex produces steroid hormones called by the general term corticosteroids<\/a>, of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and androgens<\/a>\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\n
- The adrenal medulla produces non-steroid catecholamine hormones, including adrenaline<\/a> and noradrenaline<\/a>. These hormones stimulate the fight-or-flight response<\/a>.<\/li>\n
- Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include Cushing\u2019s syndrome<\/a>, in which there is hypersecretion of cortisol, and Addison\u2019s disease<\/a>, in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n9.6 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the structure and location of the adrenal glands.<\/li>\n
- \n\n
Disorders of the Adrenal Glands<\/h1>\r\n<\/div>\r\nDisorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.\r\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\r\nHypersecretion of the glucocorticoid hormone [pb_glossary id=\"5959\"]cortisol[\/pb_glossary] leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary].<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.\r\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\r\n[caption id=\"attachment_3494\" align=\"alignleft\" width=\"475\"] Figure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em>[\/caption]\r\n\r\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary].<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.\r\n\r\nFeature: My Human Body<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_3495\" align=\"aligncenter\" width=\"877\"] Figure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline \"junkie's\" day!\u00a0<\/em>[\/caption]\r\n\r\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.\r\n\r\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.\r\n\r\nAdrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.\r\n\r\nWhile some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.\r\n\r\n\r\n9.6 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5869\"]adrenal glands[\/pb_glossary]\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the [pb_glossary id=\"5867\"]adrenal cortex[\/pb_glossary] and an inner layer called the [pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary].<\/li>\r\n \t
- The adrenal cortex produces steroid hormones called by the general term [pb_glossary id=\"5957\"]corticosteroids[\/pb_glossary], of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and [pb_glossary id=\"3485\"]androgens[\/pb_glossary]\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\r\n \t
- The adrenal medulla produces non-steroid catecholamine hormones, including [pb_glossary id=\"5875\"]adrenaline[\/pb_glossary] and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary]. These hormones stimulate the [pb_glossary id=\"6013\"]fight-or-flight response[\/pb_glossary].<\/li>\r\n \t
- Disorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include [pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary], in which there is hypersecretion of cortisol, and [pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary], in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the structure and location of the adrenal glands.<\/li>\r\n \t
- [h5p id=\"577\"]<\/li>\r\n \t
- Compare and contrast the adrenal cortex and adrenal medulla.<\/li>\r\n \t
- Identify the three layers of the adrenal cortex and the type of hormones each layer produces.<\/li>\r\n \t
- Give an example of each type of corticosteroid and state its function.<\/li>\r\n \t
- Explain how the production of glucocorticoids is regulated.<\/li>\r\n \t
- What is a catecholamine? Give an example of a catecholamine and state its function.<\/li>\r\n \t
- Compare and contrast Cushing\u2019s syndrome and Addison\u2019s disease.<\/li>\r\n \t
- What are two ways in which the nervous system (which includes the brain, spinal cord, and nerves) controls the adrenal gland?<\/li>\r\n \t
- Explain why a pituitary tumor can cause either hypersecretion or hyposecretion of cortisol.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU\r\nHow stress affects your body - Sharon Horesh Bergquist, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=WuyPuH9ojCE&feature=emb_logo\r\n
How stress affects your brain - Madhumita Murgia, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=emb_logo\r\n
Adrenaline: Fight or Flight Response, Henk van 't Klooster, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 9.6.1<\/strong>\r\n\r\nAttack from wikimedia commons<\/a> by Jerry Kirkhart<\/a> from Los Osos, Calif. on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 9.6.2<\/strong>\r\n\r\nDiagram_showing_where_the_adrenal_glands_are_in_the_body_CRUK_415.svg<\/a> by Cancer Research UK uploader<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 9.6.3<\/strong>\r\n\r\nAdrenal_cortex_labelled<\/a> by Jpogi<\/a>\u00a0at\u00a0English Wikipedia<\/a> on Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en) license.\r\n\r\nFigure 9.6.4<\/strong>\r\n\r\nThe_Adrenal_Glands<\/a> by OpenStax College<\/a> is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.5<\/strong>\r\n\r\nACTH negative feedback loop by Christinelmiller is used under a\u00a0CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.6<\/strong>\r\n\r\nA_69-Year-Old_Female_with_Tiredness_and_a_Persistent_Tan_01<\/a>\u00a0by Petros Perros<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.5\/deed.en) license.\r\n\r\nFigure 9.6.7<\/strong>\r\n\r\nBASE_Jumping_from_Sapphire_Tower_in_Istanbul<\/a> by Kontizas Dimitrios on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/3.0) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 17.17 Adrenal glands [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 17.6). OpenStax College. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/17-6-the-adrenal-glands<\/p>\r\nHenk van 't Klooster. (2013). Adrenaline: Fight or flight response. YouTube. https:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=youtu.be<\/p>\r\n
Perros, P. (2005). A 69-year-old female with tiredness and a persistent tan. PLoS Medicine,<\/em> 2(8): e229. https:\/\/doi.org\/10.1371\/journal.pmed.0020229<\/p>\r\nTED-Ed. (2015, October 22). How stress affects your body - Sharon Horesh Bergquist. YouTube. https:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, November 6). How stress affects your brain - Madhumita Murgia. YouTube. https:\/\/www.youtube.com\/watch?v=WuyPuH9ojCE&feature=youtu.be<\/p>\r\n \r\n\r\n ","rendered":"
<\/p>\nFigure 9.6.1 Got your nose!<\/em><\/figcaption><\/figure>\n\nEek!<\/h1>\n<\/div>\n
Being bitten on the nose by an eel certainly qualifies as a frightening experience! The fear this man is experiencing produces the same physiological responses in most people\u00a0\u2014\u00a0racing heart, rapid breathing, clammy hands. These and other fight-or-flight responses<\/a>\u00a0prepare the body to either defend itself or run away from danger. Why does fear elicit these changes in the body? The responses occur in large part because of hormones secreted by the adrenal glands.<\/p>\n\nIntroduction to the Adrenal Glands<\/h1>\n<\/div>\nFigure 9.6.2 Each of the two adrenal glands is found above a kidney.<\/em><\/figcaption><\/figure>\nThe\u00a0adrenal glands<\/a><\/strong> are endocrine glands that produce a variety of hormones. Adrenal hormones include the fight-or-flight hormone adrenaline and the steroid hormone cortisol. The two adrenal glands are located on both sides of the body, just above the kidneys, as shown in Figure 9.6.2. The right adrenal gland (on the left in the figure) is smaller and has a pyramidal shape. The left adrenal gland (on the right in the figure) is larger and has a half-moon shape.<\/p>\nEach adrenal gland has two distinct parts, and each part has a different function, although both parts produce hormones. There is an outer layer, called the adrenal cortex, which produces steroid hormones including cortisol. There is also an inner layer, called the adrenal medulla, which produces non-steroid hormones including adrenaline.<\/p>\n
\nAdrenal Cortex<\/h1>\n<\/div>\n
The\u00a0adrenal cortex<\/a>,<\/strong> or outer layer of the adrenal gland, is divided into three additional layers, called zones (see Figure 9.6.3). Each zone has distinct enzymes that produce different hormones from the common precursor molecule cholesterol, which is a lipid.<\/p>\n\n- Zona glomerulosa<\/a><\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\n
- Zona fasciculata<\/a><\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\n
- Zona reticularis<\/a><\/strong>\u00a0is the innermost layer of the adrenal cortex. It is directly adjacent to the medulla of the adrenal gland.<\/li>\n<\/ol>\n
Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em><\/figcaption><\/figure>\n <\/p>\n
\nTypes of Adrenal Cortex Hormones<\/span><\/p>\n<\/div>\nHormones produced by the adrenal cortex are\u00a0known\u00a0by the general term\u00a0corticosteroids<\/a>.<\/strong> As steroid hormones<\/a>, corticosteroids are endocrine hormones that are made of lipids<\/a> and exert their effects on target cells<\/a> by crossing the plasma membrane<\/a> and binding with receptors within the cytoplasm. A steroid hormone and its receptor form a complex that enters the cell nucleus<\/a> and affects gene expression<\/a>. There are three types of corticosteroids synthesized and secreted by the adrenal cortex. Each type is produced by a different zone of the adrenal cortex, as shown in Figure 9.6.4.<\/p>\nFigure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em><\/figcaption><\/figure>\nMineralocorticoids<\/h3>\n
Mineralocorticoids are produced in the zona glomerulosa<\/a> and include the hormone aldosterone<\/a>. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.<\/p>\nGlucocorticoids<\/h3>\n
Glucocorticoids are produced in the zona fasciculata<\/a> and include the hormone\u00a0cortisol<\/a>,\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of proteins<\/a>, fats, and sugars. In general, they increase the level of glucose<\/a> and fatty acids<\/a> circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.<\/p>\nAndrogens<\/h3>\n
Androgens<\/a><\/strong>\u00a0are produced in the zona reticularis<\/a> and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as testosterone<\/a> in the male gonads (testes<\/a>). In adult females, they are converted to female sex hormones called estrogens<\/a>\u00a0in the female gonads (ovaries<\/a>).<\/p>\nRegulation of Adrenal Cortex Hormones<\/h2>\n
Steroid hormone<\/a> production by the three zones of the adrenal cortex is regulated by hormones secreted by the anterior<\/a> lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide negative feedback<\/a> to the hypothalamus<\/a> and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.<\/p>\nFigure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em><\/figcaption><\/figure>\n\nAdrenal Medulla<\/h1>\n<\/div>\n
The\u00a0adrenal medulla<\/a><\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0catecholamines<\/a><\/strong>, and they include\u00a0adrenaline<\/a><\/strong>\u00a0(also called epinephrine) and noradrenaline<\/a> (also called norepinephrine). These water-soluble, non-steroid hormones<\/a>\u00a0are made of amino acids<\/a>. As non-steroid hormones, they cannot cross the plasma membrane<\/a> of target cells<\/a>. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.<\/p>\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the sympathetic division<\/a> of the autonomic nervous system<\/a>.<\/p>\n\nDisorders of the Adrenal Glands<\/h1>\n<\/div>\n
Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.<\/p>\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\n
Hypersecretion of the glucocorticoid hormone cortisol<\/a> leads to a disorder\u00a0called\u00a0Cushing\u2019s syndrome<\/a>.<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.<\/p>\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\nFigure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em><\/figcaption><\/figure>\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0Addison\u2019s disease<\/a>.<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.<\/p>\n\nFeature: My Human Body<\/h1>\n<\/div>\nFigure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline “junkie’s” day!\u00a0<\/em><\/figcaption><\/figure>\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.<\/p>\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.<\/p>\n
Adrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.<\/p>\n
While some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.<\/p>\n
\n\n\n9.6 Summary<\/span><\/h1>\n<\/header>\n\n\n- The adrenal glands<\/a>\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the adrenal cortex<\/a> and an inner layer called the adrenal medulla<\/a>.<\/li>\n
- The adrenal cortex produces steroid hormones called by the general term corticosteroids<\/a>, of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and androgens<\/a>\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\n
- The adrenal medulla produces non-steroid catecholamine hormones, including adrenaline<\/a> and noradrenaline<\/a>. These hormones stimulate the fight-or-flight response<\/a>.<\/li>\n
- Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include Cushing\u2019s syndrome<\/a>, in which there is hypersecretion of cortisol, and Addison\u2019s disease<\/a>, in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n9.6 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the structure and location of the adrenal glands.<\/li>\n
- \n\n
Adrenal Hyposecretion: Addison\u2019s Disease<\/h2>\r\n[caption id=\"attachment_3494\" align=\"alignleft\" width=\"475\"] Figure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em>[\/caption]\r\n\r\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0[pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary].<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.\r\n\r\nFeature: My Human Body<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_3495\" align=\"aligncenter\" width=\"877\"] Figure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline \"junkie's\" day!\u00a0<\/em>[\/caption]\r\n\r\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.\r\n\r\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.\r\n\r\nAdrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.\r\n\r\nWhile some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.\r\n\r\n\r\n9.6 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5869\"]adrenal glands[\/pb_glossary]\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the [pb_glossary id=\"5867\"]adrenal cortex[\/pb_glossary] and an inner layer called the [pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary].<\/li>\r\n \t
- The adrenal cortex produces steroid hormones called by the general term [pb_glossary id=\"5957\"]corticosteroids[\/pb_glossary], of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and [pb_glossary id=\"3485\"]androgens[\/pb_glossary]\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\r\n \t
- The adrenal medulla produces non-steroid catecholamine hormones, including [pb_glossary id=\"5875\"]adrenaline[\/pb_glossary] and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary]. These hormones stimulate the [pb_glossary id=\"6013\"]fight-or-flight response[\/pb_glossary].<\/li>\r\n \t
- Disorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include [pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary], in which there is hypersecretion of cortisol, and [pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary], in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the structure and location of the adrenal glands.<\/li>\r\n \t
- [h5p id=\"577\"]<\/li>\r\n \t
- Compare and contrast the adrenal cortex and adrenal medulla.<\/li>\r\n \t
- Identify the three layers of the adrenal cortex and the type of hormones each layer produces.<\/li>\r\n \t
- Give an example of each type of corticosteroid and state its function.<\/li>\r\n \t
- Explain how the production of glucocorticoids is regulated.<\/li>\r\n \t
- What is a catecholamine? Give an example of a catecholamine and state its function.<\/li>\r\n \t
- Compare and contrast Cushing\u2019s syndrome and Addison\u2019s disease.<\/li>\r\n \t
- What are two ways in which the nervous system (which includes the brain, spinal cord, and nerves) controls the adrenal gland?<\/li>\r\n \t
- Explain why a pituitary tumor can cause either hypersecretion or hyposecretion of cortisol.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU\r\nHow stress affects your body - Sharon Horesh Bergquist, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=WuyPuH9ojCE&feature=emb_logo\r\n
How stress affects your brain - Madhumita Murgia, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=emb_logo\r\n
Adrenaline: Fight or Flight Response, Henk van 't Klooster, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 9.6.1<\/strong>\r\n\r\nAttack from wikimedia commons<\/a> by Jerry Kirkhart<\/a> from Los Osos, Calif. on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 9.6.2<\/strong>\r\n\r\nDiagram_showing_where_the_adrenal_glands_are_in_the_body_CRUK_415.svg<\/a> by Cancer Research UK uploader<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 9.6.3<\/strong>\r\n\r\nAdrenal_cortex_labelled<\/a> by Jpogi<\/a>\u00a0at\u00a0English Wikipedia<\/a> on Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en) license.\r\n\r\nFigure 9.6.4<\/strong>\r\n\r\nThe_Adrenal_Glands<\/a> by OpenStax College<\/a> is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.5<\/strong>\r\n\r\nACTH negative feedback loop by Christinelmiller is used under a\u00a0CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.6<\/strong>\r\n\r\nA_69-Year-Old_Female_with_Tiredness_and_a_Persistent_Tan_01<\/a>\u00a0by Petros Perros<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.5\/deed.en) license.\r\n\r\nFigure 9.6.7<\/strong>\r\n\r\nBASE_Jumping_from_Sapphire_Tower_in_Istanbul<\/a> by Kontizas Dimitrios on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/3.0) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 17.17 Adrenal glands [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 17.6). OpenStax College. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/17-6-the-adrenal-glands<\/p>\r\nHenk van 't Klooster. (2013). Adrenaline: Fight or flight response. YouTube. https:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=youtu.be<\/p>\r\n
Perros, P. (2005). A 69-year-old female with tiredness and a persistent tan. PLoS Medicine,<\/em> 2(8): e229. https:\/\/doi.org\/10.1371\/journal.pmed.0020229<\/p>\r\nTED-Ed. (2015, October 22). How stress affects your body - Sharon Horesh Bergquist. YouTube. https:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, November 6). How stress affects your brain - Madhumita Murgia. YouTube. https:\/\/www.youtube.com\/watch?v=WuyPuH9ojCE&feature=youtu.be<\/p>\r\n \r\n\r\n ","rendered":"
<\/p>\nFigure 9.6.1 Got your nose!<\/em><\/figcaption><\/figure>\n\nEek!<\/h1>\n<\/div>\n
Being bitten on the nose by an eel certainly qualifies as a frightening experience! The fear this man is experiencing produces the same physiological responses in most people\u00a0\u2014\u00a0racing heart, rapid breathing, clammy hands. These and other fight-or-flight responses<\/a>\u00a0prepare the body to either defend itself or run away from danger. Why does fear elicit these changes in the body? The responses occur in large part because of hormones secreted by the adrenal glands.<\/p>\n\nIntroduction to the Adrenal Glands<\/h1>\n<\/div>\nFigure 9.6.2 Each of the two adrenal glands is found above a kidney.<\/em><\/figcaption><\/figure>\nThe\u00a0adrenal glands<\/a><\/strong> are endocrine glands that produce a variety of hormones. Adrenal hormones include the fight-or-flight hormone adrenaline and the steroid hormone cortisol. The two adrenal glands are located on both sides of the body, just above the kidneys, as shown in Figure 9.6.2. The right adrenal gland (on the left in the figure) is smaller and has a pyramidal shape. The left adrenal gland (on the right in the figure) is larger and has a half-moon shape.<\/p>\nEach adrenal gland has two distinct parts, and each part has a different function, although both parts produce hormones. There is an outer layer, called the adrenal cortex, which produces steroid hormones including cortisol. There is also an inner layer, called the adrenal medulla, which produces non-steroid hormones including adrenaline.<\/p>\n
\nAdrenal Cortex<\/h1>\n<\/div>\n
The\u00a0adrenal cortex<\/a>,<\/strong> or outer layer of the adrenal gland, is divided into three additional layers, called zones (see Figure 9.6.3). Each zone has distinct enzymes that produce different hormones from the common precursor molecule cholesterol, which is a lipid.<\/p>\n\n- Zona glomerulosa<\/a><\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\n
- Zona fasciculata<\/a><\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\n
- Zona reticularis<\/a><\/strong>\u00a0is the innermost layer of the adrenal cortex. It is directly adjacent to the medulla of the adrenal gland.<\/li>\n<\/ol>\n
Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em><\/figcaption><\/figure>\n <\/p>\n
\nTypes of Adrenal Cortex Hormones<\/span><\/p>\n<\/div>\nHormones produced by the adrenal cortex are\u00a0known\u00a0by the general term\u00a0corticosteroids<\/a>.<\/strong> As steroid hormones<\/a>, corticosteroids are endocrine hormones that are made of lipids<\/a> and exert their effects on target cells<\/a> by crossing the plasma membrane<\/a> and binding with receptors within the cytoplasm. A steroid hormone and its receptor form a complex that enters the cell nucleus<\/a> and affects gene expression<\/a>. There are three types of corticosteroids synthesized and secreted by the adrenal cortex. Each type is produced by a different zone of the adrenal cortex, as shown in Figure 9.6.4.<\/p>\nFigure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em><\/figcaption><\/figure>\nMineralocorticoids<\/h3>\n
Mineralocorticoids are produced in the zona glomerulosa<\/a> and include the hormone aldosterone<\/a>. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.<\/p>\nGlucocorticoids<\/h3>\n
Glucocorticoids are produced in the zona fasciculata<\/a> and include the hormone\u00a0cortisol<\/a>,\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of proteins<\/a>, fats, and sugars. In general, they increase the level of glucose<\/a> and fatty acids<\/a> circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.<\/p>\nAndrogens<\/h3>\n
Androgens<\/a><\/strong>\u00a0are produced in the zona reticularis<\/a> and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as testosterone<\/a> in the male gonads (testes<\/a>). In adult females, they are converted to female sex hormones called estrogens<\/a>\u00a0in the female gonads (ovaries<\/a>).<\/p>\nRegulation of Adrenal Cortex Hormones<\/h2>\n
Steroid hormone<\/a> production by the three zones of the adrenal cortex is regulated by hormones secreted by the anterior<\/a> lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide negative feedback<\/a> to the hypothalamus<\/a> and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.<\/p>\nFigure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em><\/figcaption><\/figure>\n\nAdrenal Medulla<\/h1>\n<\/div>\n
The\u00a0adrenal medulla<\/a><\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0catecholamines<\/a><\/strong>, and they include\u00a0adrenaline<\/a><\/strong>\u00a0(also called epinephrine) and noradrenaline<\/a> (also called norepinephrine). These water-soluble, non-steroid hormones<\/a>\u00a0are made of amino acids<\/a>. As non-steroid hormones, they cannot cross the plasma membrane<\/a> of target cells<\/a>. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.<\/p>\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the sympathetic division<\/a> of the autonomic nervous system<\/a>.<\/p>\n\nDisorders of the Adrenal Glands<\/h1>\n<\/div>\n
Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.<\/p>\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\n
Hypersecretion of the glucocorticoid hormone cortisol<\/a> leads to a disorder\u00a0called\u00a0Cushing\u2019s syndrome<\/a>.<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.<\/p>\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\nFigure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em><\/figcaption><\/figure>\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0Addison\u2019s disease<\/a>.<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.<\/p>\n\nFeature: My Human Body<\/h1>\n<\/div>\nFigure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline “junkie’s” day!\u00a0<\/em><\/figcaption><\/figure>\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.<\/p>\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.<\/p>\n
Adrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.<\/p>\n
While some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.<\/p>\n
\n\n\n9.6 Summary<\/span><\/h1>\n<\/header>\n\n\n- The adrenal glands<\/a>\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the adrenal cortex<\/a> and an inner layer called the adrenal medulla<\/a>.<\/li>\n
- The adrenal cortex produces steroid hormones called by the general term corticosteroids<\/a>, of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and androgens<\/a>\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\n
- The adrenal medulla produces non-steroid catecholamine hormones, including adrenaline<\/a> and noradrenaline<\/a>. These hormones stimulate the fight-or-flight response<\/a>.<\/li>\n
- Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include Cushing\u2019s syndrome<\/a>, in which there is hypersecretion of cortisol, and Addison\u2019s disease<\/a>, in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n9.6 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the structure and location of the adrenal glands.<\/li>\n
- \n\n
Feature: My Human Body<\/h1>\r\n<\/div>\r\n\r\n[caption id=\"attachment_3495\" align=\"aligncenter\" width=\"877\"] Figure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline \"junkie's\" day!\u00a0<\/em>[\/caption]\r\n\r\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.\r\n\r\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.\r\n\r\nAdrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.\r\n\r\nWhile some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.\r\n\r\n\r\n9.6 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5869\"]adrenal glands[\/pb_glossary]\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the [pb_glossary id=\"5867\"]adrenal cortex[\/pb_glossary] and an inner layer called the [pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary].<\/li>\r\n \t
- The adrenal cortex produces steroid hormones called by the general term [pb_glossary id=\"5957\"]corticosteroids[\/pb_glossary], of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and [pb_glossary id=\"3485\"]androgens[\/pb_glossary]\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\r\n \t
- The adrenal medulla produces non-steroid catecholamine hormones, including [pb_glossary id=\"5875\"]adrenaline[\/pb_glossary] and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary]. These hormones stimulate the [pb_glossary id=\"6013\"]fight-or-flight response[\/pb_glossary].<\/li>\r\n \t
- Disorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include [pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary], in which there is hypersecretion of cortisol, and [pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary], in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the structure and location of the adrenal glands.<\/li>\r\n \t
- [h5p id=\"577\"]<\/li>\r\n \t
- Compare and contrast the adrenal cortex and adrenal medulla.<\/li>\r\n \t
- Identify the three layers of the adrenal cortex and the type of hormones each layer produces.<\/li>\r\n \t
- Give an example of each type of corticosteroid and state its function.<\/li>\r\n \t
- Explain how the production of glucocorticoids is regulated.<\/li>\r\n \t
- What is a catecholamine? Give an example of a catecholamine and state its function.<\/li>\r\n \t
- Compare and contrast Cushing\u2019s syndrome and Addison\u2019s disease.<\/li>\r\n \t
- What are two ways in which the nervous system (which includes the brain, spinal cord, and nerves) controls the adrenal gland?<\/li>\r\n \t
- Explain why a pituitary tumor can cause either hypersecretion or hyposecretion of cortisol.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU\r\nHow stress affects your body - Sharon Horesh Bergquist, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=WuyPuH9ojCE&feature=emb_logo\r\n
How stress affects your brain - Madhumita Murgia, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=emb_logo\r\n
Adrenaline: Fight or Flight Response, Henk van 't Klooster, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 9.6.1<\/strong>\r\n\r\nAttack from wikimedia commons<\/a> by Jerry Kirkhart<\/a> from Los Osos, Calif. on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 9.6.2<\/strong>\r\n\r\nDiagram_showing_where_the_adrenal_glands_are_in_the_body_CRUK_415.svg<\/a> by Cancer Research UK uploader<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 9.6.3<\/strong>\r\n\r\nAdrenal_cortex_labelled<\/a> by Jpogi<\/a>\u00a0at\u00a0English Wikipedia<\/a> on Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en) license.\r\n\r\nFigure 9.6.4<\/strong>\r\n\r\nThe_Adrenal_Glands<\/a> by OpenStax College<\/a> is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.5<\/strong>\r\n\r\nACTH negative feedback loop by Christinelmiller is used under a\u00a0CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.6<\/strong>\r\n\r\nA_69-Year-Old_Female_with_Tiredness_and_a_Persistent_Tan_01<\/a>\u00a0by Petros Perros<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.5\/deed.en) license.\r\n\r\nFigure 9.6.7<\/strong>\r\n\r\nBASE_Jumping_from_Sapphire_Tower_in_Istanbul<\/a> by Kontizas Dimitrios on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/3.0) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 17.17 Adrenal glands [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 17.6). OpenStax College. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/17-6-the-adrenal-glands<\/p>\r\nHenk van 't Klooster. (2013). Adrenaline: Fight or flight response. YouTube. https:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=youtu.be<\/p>\r\n
Perros, P. (2005). A 69-year-old female with tiredness and a persistent tan. PLoS Medicine,<\/em> 2(8): e229. https:\/\/doi.org\/10.1371\/journal.pmed.0020229<\/p>\r\nTED-Ed. (2015, October 22). How stress affects your body - Sharon Horesh Bergquist. YouTube. https:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, November 6). How stress affects your brain - Madhumita Murgia. YouTube. https:\/\/www.youtube.com\/watch?v=WuyPuH9ojCE&feature=youtu.be<\/p>\r\n \r\n\r\n ","rendered":"
<\/p>\nFigure 9.6.1 Got your nose!<\/em><\/figcaption><\/figure>\n\nEek!<\/h1>\n<\/div>\n
Being bitten on the nose by an eel certainly qualifies as a frightening experience! The fear this man is experiencing produces the same physiological responses in most people\u00a0\u2014\u00a0racing heart, rapid breathing, clammy hands. These and other fight-or-flight responses<\/a>\u00a0prepare the body to either defend itself or run away from danger. Why does fear elicit these changes in the body? The responses occur in large part because of hormones secreted by the adrenal glands.<\/p>\n\nIntroduction to the Adrenal Glands<\/h1>\n<\/div>\nFigure 9.6.2 Each of the two adrenal glands is found above a kidney.<\/em><\/figcaption><\/figure>\nThe\u00a0adrenal glands<\/a><\/strong> are endocrine glands that produce a variety of hormones. Adrenal hormones include the fight-or-flight hormone adrenaline and the steroid hormone cortisol. The two adrenal glands are located on both sides of the body, just above the kidneys, as shown in Figure 9.6.2. The right adrenal gland (on the left in the figure) is smaller and has a pyramidal shape. The left adrenal gland (on the right in the figure) is larger and has a half-moon shape.<\/p>\nEach adrenal gland has two distinct parts, and each part has a different function, although both parts produce hormones. There is an outer layer, called the adrenal cortex, which produces steroid hormones including cortisol. There is also an inner layer, called the adrenal medulla, which produces non-steroid hormones including adrenaline.<\/p>\n
\nAdrenal Cortex<\/h1>\n<\/div>\n
The\u00a0adrenal cortex<\/a>,<\/strong> or outer layer of the adrenal gland, is divided into three additional layers, called zones (see Figure 9.6.3). Each zone has distinct enzymes that produce different hormones from the common precursor molecule cholesterol, which is a lipid.<\/p>\n\n- Zona glomerulosa<\/a><\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\n
- Zona fasciculata<\/a><\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\n
- Zona reticularis<\/a><\/strong>\u00a0is the innermost layer of the adrenal cortex. It is directly adjacent to the medulla of the adrenal gland.<\/li>\n<\/ol>\n
Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em><\/figcaption><\/figure>\n <\/p>\n
\nTypes of Adrenal Cortex Hormones<\/span><\/p>\n<\/div>\nHormones produced by the adrenal cortex are\u00a0known\u00a0by the general term\u00a0corticosteroids<\/a>.<\/strong> As steroid hormones<\/a>, corticosteroids are endocrine hormones that are made of lipids<\/a> and exert their effects on target cells<\/a> by crossing the plasma membrane<\/a> and binding with receptors within the cytoplasm. A steroid hormone and its receptor form a complex that enters the cell nucleus<\/a> and affects gene expression<\/a>. There are three types of corticosteroids synthesized and secreted by the adrenal cortex. Each type is produced by a different zone of the adrenal cortex, as shown in Figure 9.6.4.<\/p>\nFigure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em><\/figcaption><\/figure>\nMineralocorticoids<\/h3>\n
Mineralocorticoids are produced in the zona glomerulosa<\/a> and include the hormone aldosterone<\/a>. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.<\/p>\nGlucocorticoids<\/h3>\n
Glucocorticoids are produced in the zona fasciculata<\/a> and include the hormone\u00a0cortisol<\/a>,\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of proteins<\/a>, fats, and sugars. In general, they increase the level of glucose<\/a> and fatty acids<\/a> circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.<\/p>\nAndrogens<\/h3>\n
Androgens<\/a><\/strong>\u00a0are produced in the zona reticularis<\/a> and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as testosterone<\/a> in the male gonads (testes<\/a>). In adult females, they are converted to female sex hormones called estrogens<\/a>\u00a0in the female gonads (ovaries<\/a>).<\/p>\nRegulation of Adrenal Cortex Hormones<\/h2>\n
Steroid hormone<\/a> production by the three zones of the adrenal cortex is regulated by hormones secreted by the anterior<\/a> lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide negative feedback<\/a> to the hypothalamus<\/a> and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.<\/p>\nFigure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em><\/figcaption><\/figure>\n\nAdrenal Medulla<\/h1>\n<\/div>\n
The\u00a0adrenal medulla<\/a><\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0catecholamines<\/a><\/strong>, and they include\u00a0adrenaline<\/a><\/strong>\u00a0(also called epinephrine) and noradrenaline<\/a> (also called norepinephrine). These water-soluble, non-steroid hormones<\/a>\u00a0are made of amino acids<\/a>. As non-steroid hormones, they cannot cross the plasma membrane<\/a> of target cells<\/a>. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.<\/p>\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the sympathetic division<\/a> of the autonomic nervous system<\/a>.<\/p>\n\nDisorders of the Adrenal Glands<\/h1>\n<\/div>\n
Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.<\/p>\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\n
Hypersecretion of the glucocorticoid hormone cortisol<\/a> leads to a disorder\u00a0called\u00a0Cushing\u2019s syndrome<\/a>.<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.<\/p>\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\nFigure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em><\/figcaption><\/figure>\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0Addison\u2019s disease<\/a>.<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.<\/p>\n\nFeature: My Human Body<\/h1>\n<\/div>\nFigure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline “junkie’s” day!\u00a0<\/em><\/figcaption><\/figure>\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.<\/p>\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.<\/p>\n
Adrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.<\/p>\n
While some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.<\/p>\n
\n\n\n9.6 Summary<\/span><\/h1>\n<\/header>\n\n\n- The adrenal glands<\/a>\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the adrenal cortex<\/a> and an inner layer called the adrenal medulla<\/a>.<\/li>\n
- The adrenal cortex produces steroid hormones called by the general term corticosteroids<\/a>, of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and androgens<\/a>\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\n
- The adrenal medulla produces non-steroid catecholamine hormones, including adrenaline<\/a> and noradrenaline<\/a>. These hormones stimulate the fight-or-flight response<\/a>.<\/li>\n
- Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include Cushing\u2019s syndrome<\/a>, in which there is hypersecretion of cortisol, and Addison\u2019s disease<\/a>, in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n9.6 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the structure and location of the adrenal glands.<\/li>\n
- \n\n
9.6 Summary<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- The [pb_glossary id=\"5869\"]adrenal glands[\/pb_glossary]\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the [pb_glossary id=\"5867\"]adrenal cortex[\/pb_glossary] and an inner layer called the [pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary].<\/li>\r\n \t
- The adrenal cortex produces steroid hormones called by the general term [pb_glossary id=\"5957\"]corticosteroids[\/pb_glossary], of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and [pb_glossary id=\"3485\"]androgens[\/pb_glossary]\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\r\n \t
- The adrenal medulla produces non-steroid catecholamine hormones, including [pb_glossary id=\"5875\"]adrenaline[\/pb_glossary] and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary]. These hormones stimulate the [pb_glossary id=\"6013\"]fight-or-flight response[\/pb_glossary].<\/li>\r\n \t
- Disorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include [pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary], in which there is hypersecretion of cortisol, and [pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary], in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Review Questions<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\n \t- Describe the structure and location of the adrenal glands.<\/li>\r\n \t
- [h5p id=\"577\"]<\/li>\r\n \t
- Compare and contrast the adrenal cortex and adrenal medulla.<\/li>\r\n \t
- Identify the three layers of the adrenal cortex and the type of hormones each layer produces.<\/li>\r\n \t
- Give an example of each type of corticosteroid and state its function.<\/li>\r\n \t
- Explain how the production of glucocorticoids is regulated.<\/li>\r\n \t
- What is a catecholamine? Give an example of a catecholamine and state its function.<\/li>\r\n \t
- Compare and contrast Cushing\u2019s syndrome and Addison\u2019s disease.<\/li>\r\n \t
- What are two ways in which the nervous system (which includes the brain, spinal cord, and nerves) controls the adrenal gland?<\/li>\r\n \t
- Explain why a pituitary tumor can cause either hypersecretion or hyposecretion of cortisol.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n9.6 Explore More<\/span><\/h1>\r\n<\/header>\r\n\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU\r\nHow stress affects your body - Sharon Horesh Bergquist, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=WuyPuH9ojCE&feature=emb_logo\r\n
How stress affects your brain - Madhumita Murgia, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=emb_logo\r\n
Adrenaline: Fight or Flight Response, Henk van 't Klooster, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 9.6.1<\/strong>\r\n\r\nAttack from wikimedia commons<\/a> by Jerry Kirkhart<\/a> from Los Osos, Calif. on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 9.6.2<\/strong>\r\n\r\nDiagram_showing_where_the_adrenal_glands_are_in_the_body_CRUK_415.svg<\/a> by Cancer Research UK uploader<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 9.6.3<\/strong>\r\n\r\nAdrenal_cortex_labelled<\/a> by Jpogi<\/a>\u00a0at\u00a0English Wikipedia<\/a> on Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en) license.\r\n\r\nFigure 9.6.4<\/strong>\r\n\r\nThe_Adrenal_Glands<\/a> by OpenStax College<\/a> is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.5<\/strong>\r\n\r\nACTH negative feedback loop by Christinelmiller is used under a\u00a0CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.6<\/strong>\r\n\r\nA_69-Year-Old_Female_with_Tiredness_and_a_Persistent_Tan_01<\/a>\u00a0by Petros Perros<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.5\/deed.en) license.\r\n\r\nFigure 9.6.7<\/strong>\r\n\r\nBASE_Jumping_from_Sapphire_Tower_in_Istanbul<\/a> by Kontizas Dimitrios on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/3.0) license.\r\nReferences<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 17.17 Adrenal glands [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 17.6). OpenStax College. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/17-6-the-adrenal-glands<\/p>\r\nHenk van 't Klooster. (2013). Adrenaline: Fight or flight response. YouTube. https:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=youtu.be<\/p>\r\n
Perros, P. (2005). A 69-year-old female with tiredness and a persistent tan. PLoS Medicine,<\/em> 2(8): e229. https:\/\/doi.org\/10.1371\/journal.pmed.0020229<\/p>\r\nTED-Ed. (2015, October 22). How stress affects your body - Sharon Horesh Bergquist. YouTube. https:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, November 6). How stress affects your brain - Madhumita Murgia. YouTube. https:\/\/www.youtube.com\/watch?v=WuyPuH9ojCE&feature=youtu.be<\/p>\r\n \r\n\r\n ","rendered":"
<\/p>\nFigure 9.6.1 Got your nose!<\/em><\/figcaption><\/figure>\n\nEek!<\/h1>\n<\/div>\n
Being bitten on the nose by an eel certainly qualifies as a frightening experience! The fear this man is experiencing produces the same physiological responses in most people\u00a0\u2014\u00a0racing heart, rapid breathing, clammy hands. These and other fight-or-flight responses<\/a>\u00a0prepare the body to either defend itself or run away from danger. Why does fear elicit these changes in the body? The responses occur in large part because of hormones secreted by the adrenal glands.<\/p>\n\nIntroduction to the Adrenal Glands<\/h1>\n<\/div>\nFigure 9.6.2 Each of the two adrenal glands is found above a kidney.<\/em><\/figcaption><\/figure>\nThe\u00a0adrenal glands<\/a><\/strong> are endocrine glands that produce a variety of hormones. Adrenal hormones include the fight-or-flight hormone adrenaline and the steroid hormone cortisol. The two adrenal glands are located on both sides of the body, just above the kidneys, as shown in Figure 9.6.2. The right adrenal gland (on the left in the figure) is smaller and has a pyramidal shape. The left adrenal gland (on the right in the figure) is larger and has a half-moon shape.<\/p>\nEach adrenal gland has two distinct parts, and each part has a different function, although both parts produce hormones. There is an outer layer, called the adrenal cortex, which produces steroid hormones including cortisol. There is also an inner layer, called the adrenal medulla, which produces non-steroid hormones including adrenaline.<\/p>\n
\nAdrenal Cortex<\/h1>\n<\/div>\n
The\u00a0adrenal cortex<\/a>,<\/strong> or outer layer of the adrenal gland, is divided into three additional layers, called zones (see Figure 9.6.3). Each zone has distinct enzymes that produce different hormones from the common precursor molecule cholesterol, which is a lipid.<\/p>\n\n- Zona glomerulosa<\/a><\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\n
- Zona fasciculata<\/a><\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\n
- Zona reticularis<\/a><\/strong>\u00a0is the innermost layer of the adrenal cortex. It is directly adjacent to the medulla of the adrenal gland.<\/li>\n<\/ol>\n
Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em><\/figcaption><\/figure>\n <\/p>\n
\nTypes of Adrenal Cortex Hormones<\/span><\/p>\n<\/div>\nHormones produced by the adrenal cortex are\u00a0known\u00a0by the general term\u00a0corticosteroids<\/a>.<\/strong> As steroid hormones<\/a>, corticosteroids are endocrine hormones that are made of lipids<\/a> and exert their effects on target cells<\/a> by crossing the plasma membrane<\/a> and binding with receptors within the cytoplasm. A steroid hormone and its receptor form a complex that enters the cell nucleus<\/a> and affects gene expression<\/a>. There are three types of corticosteroids synthesized and secreted by the adrenal cortex. Each type is produced by a different zone of the adrenal cortex, as shown in Figure 9.6.4.<\/p>\nFigure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em><\/figcaption><\/figure>\nMineralocorticoids<\/h3>\n
Mineralocorticoids are produced in the zona glomerulosa<\/a> and include the hormone aldosterone<\/a>. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.<\/p>\nGlucocorticoids<\/h3>\n
Glucocorticoids are produced in the zona fasciculata<\/a> and include the hormone\u00a0cortisol<\/a>,\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of proteins<\/a>, fats, and sugars. In general, they increase the level of glucose<\/a> and fatty acids<\/a> circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.<\/p>\nAndrogens<\/h3>\n
Androgens<\/a><\/strong>\u00a0are produced in the zona reticularis<\/a> and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as testosterone<\/a> in the male gonads (testes<\/a>). In adult females, they are converted to female sex hormones called estrogens<\/a>\u00a0in the female gonads (ovaries<\/a>).<\/p>\nRegulation of Adrenal Cortex Hormones<\/h2>\n
Steroid hormone<\/a> production by the three zones of the adrenal cortex is regulated by hormones secreted by the anterior<\/a> lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide negative feedback<\/a> to the hypothalamus<\/a> and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.<\/p>\nFigure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em><\/figcaption><\/figure>\n\nAdrenal Medulla<\/h1>\n<\/div>\n
The\u00a0adrenal medulla<\/a><\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0catecholamines<\/a><\/strong>, and they include\u00a0adrenaline<\/a><\/strong>\u00a0(also called epinephrine) and noradrenaline<\/a> (also called norepinephrine). These water-soluble, non-steroid hormones<\/a>\u00a0are made of amino acids<\/a>. As non-steroid hormones, they cannot cross the plasma membrane<\/a> of target cells<\/a>. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.<\/p>\nCatecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the sympathetic division<\/a> of the autonomic nervous system<\/a>.<\/p>\n\nDisorders of the Adrenal Glands<\/h1>\n<\/div>\n
Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.<\/p>\nAdrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\n
Hypersecretion of the glucocorticoid hormone cortisol<\/a> leads to a disorder\u00a0called\u00a0Cushing\u2019s syndrome<\/a>.<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.<\/p>\nAdrenal Hyposecretion: Addison\u2019s Disease<\/h2>\nFigure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em><\/figcaption><\/figure>\nHyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0Addison\u2019s disease<\/a>.<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.<\/p>\n\nFeature: My Human Body<\/h1>\n<\/div>\nFigure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline “junkie’s” day!\u00a0<\/em><\/figcaption><\/figure>\nDoes just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.<\/p>\nPeople who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.<\/p>\n
Adrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.<\/p>\n
While some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.<\/p>\n
\n\n\n9.6 Summary<\/span><\/h1>\n<\/header>\n\n\n- The adrenal glands<\/a>\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the adrenal cortex<\/a> and an inner layer called the adrenal medulla<\/a>.<\/li>\n
- The adrenal cortex produces steroid hormones called by the general term corticosteroids<\/a>, of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and androgens<\/a>\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\n
- The adrenal medulla produces non-steroid catecholamine hormones, including adrenaline<\/a> and noradrenaline<\/a>. These hormones stimulate the fight-or-flight response<\/a>.<\/li>\n
- Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include Cushing\u2019s syndrome<\/a>, in which there is hypersecretion of cortisol, and Addison\u2019s disease<\/a>, in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n\n
\n9.6 Review Questions<\/span><\/h1>\n<\/header>\n\n\n- Describe the structure and location of the adrenal glands.<\/li>\n
- \n\n
- \r\n \t
- The [pb_glossary id=\"5869\"]adrenal glands[\/pb_glossary]\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the [pb_glossary id=\"5867\"]adrenal cortex[\/pb_glossary] and an inner layer called the [pb_glossary id=\"5873\"]adrenal medulla[\/pb_glossary].<\/li>\r\n \t
- The adrenal cortex produces steroid hormones called by the general term [pb_glossary id=\"5957\"]corticosteroids[\/pb_glossary], of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and [pb_glossary id=\"3485\"]androgens[\/pb_glossary]\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\r\n \t
- The adrenal medulla produces non-steroid catecholamine hormones, including [pb_glossary id=\"5875\"]adrenaline[\/pb_glossary] and [pb_glossary id=\"3491\"]noradrenaline[\/pb_glossary]. These hormones stimulate the [pb_glossary id=\"6013\"]fight-or-flight response[\/pb_glossary].<\/li>\r\n \t
- Disorders of the adrenal glands generally include either [pb_glossary id=\"3413\"]hypersecretion[\/pb_glossary] or [pb_glossary id=\"3414\"]hyposecretion[\/pb_glossary] of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include [pb_glossary id=\"3492\"]Cushing\u2019s syndrome[\/pb_glossary], in which there is hypersecretion of cortisol, and [pb_glossary id=\"3493\"]Addison\u2019s disease[\/pb_glossary], in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n
\r\n 9.6 Review Questions<\/span><\/h1>\r\n<\/header>\r\n
\r\n- \r\n \t
- Describe the structure and location of the adrenal glands.<\/li>\r\n \t
- [h5p id=\"577\"]<\/li>\r\n \t
- Compare and contrast the adrenal cortex and adrenal medulla.<\/li>\r\n \t
- Identify the three layers of the adrenal cortex and the type of hormones each layer produces.<\/li>\r\n \t
- Give an example of each type of corticosteroid and state its function.<\/li>\r\n \t
- Explain how the production of glucocorticoids is regulated.<\/li>\r\n \t
- What is a catecholamine? Give an example of a catecholamine and state its function.<\/li>\r\n \t
- Compare and contrast Cushing\u2019s syndrome and Addison\u2019s disease.<\/li>\r\n \t
- What are two ways in which the nervous system (which includes the brain, spinal cord, and nerves) controls the adrenal gland?<\/li>\r\n \t
- Explain why a pituitary tumor can cause either hypersecretion or hyposecretion of cortisol.<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n
\r\n 9.6 Explore More<\/span><\/h1>\r\n<\/header>\r\n
\r\n\r\nhttps:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU\r\nHow stress affects your body - Sharon Horesh Bergquist, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?time_continue=1&v=WuyPuH9ojCE&feature=emb_logo\r\n
How stress affects your brain - Madhumita Murgia, TED-Ed, 2015.<\/p>\r\nhttps:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=emb_logo\r\n
Adrenaline: Fight or Flight Response, Henk van 't Klooster, 2013.<\/p>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n
Attributions<\/h2>\r\nFigure 9.6.1<\/strong>\r\n\r\nAttack from wikimedia commons<\/a> by Jerry Kirkhart<\/a> from Los Osos, Calif. on Wikimedia Commons is used under a CC BY 2.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.0) license.\r\n\r\nFigure 9.6.2<\/strong>\r\n\r\nDiagram_showing_where_the_adrenal_glands_are_in_the_body_CRUK_415.svg<\/a> by Cancer Research UK uploader<\/a> on Wikimedia Commons is used under a CC BY-SA 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0) license.\r\n\r\nFigure 9.6.3<\/strong>\r\n\r\nAdrenal_cortex_labelled<\/a> by Jpogi<\/a>\u00a0at\u00a0English Wikipedia<\/a> on Wikimedia Commons is used under a CC0 1.0<\/a> Universal Public Domain Dedication (https:\/\/creativecommons.org\/publicdomain\/zero\/1.0\/deed.en) license.\r\n\r\nFigure 9.6.4<\/strong>\r\n\r\nThe_Adrenal_Glands<\/a> by OpenStax College<\/a> is used under a CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.5<\/strong>\r\n\r\nACTH negative feedback loop by Christinelmiller is used under a\u00a0CC BY 4.0<\/a> (https:\/\/creativecommons.org\/licenses\/by\/4.0\/) license.\r\n\r\nFigure 9.6.6<\/strong>\r\n\r\nA_69-Year-Old_Female_with_Tiredness_and_a_Persistent_Tan_01<\/a>\u00a0by Petros Perros<\/a> on Wikimedia Commons is used under a CC BY 2.5<\/a> (https:\/\/creativecommons.org\/licenses\/by\/2.5\/deed.en) license.\r\n\r\nFigure 9.6.7<\/strong>\r\n\r\nBASE_Jumping_from_Sapphire_Tower_in_Istanbul<\/a> by Kontizas Dimitrios on Wikimedia Commons is used under a CC BY-SA 3.0<\/a> (https:\/\/creativecommons.org\/licenses\/by-sa\/3.0) license.\r\n
References<\/h2>\r\n
Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, June 19). Figure 17.17 Adrenal glands [digital image].\u00a0 In Anatomy and Physiology<\/em> (Section 17.6). OpenStax College. https:\/\/openstax.org\/books\/anatomy-and-physiology\/pages\/17-6-the-adrenal-glands<\/p>\r\n
Henk van 't Klooster. (2013). Adrenaline: Fight or flight response. YouTube. https:\/\/www.youtube.com\/watch?v=FBnBTkcr6No&feature=youtu.be<\/p>\r\n
Perros, P. (2005). A 69-year-old female with tiredness and a persistent tan. PLoS Medicine,<\/em> 2(8): e229. https:\/\/doi.org\/10.1371\/journal.pmed.0020229<\/p>\r\n
TED-Ed. (2015, October 22). How stress affects your body - Sharon Horesh Bergquist. YouTube. https:\/\/www.youtube.com\/watch?v=v-t1Z5-oPtU&feature=youtu.be<\/p>\r\n
TED-Ed. (2015, November 6). How stress affects your brain - Madhumita Murgia. YouTube. https:\/\/www.youtube.com\/watch?v=WuyPuH9ojCE&feature=youtu.be<\/p>\r\n \r\n\r\n ","rendered":"
<\/p>\n
Figure 9.6.1 Got your nose!<\/em><\/figcaption><\/figure>\n \nEek!<\/h1>\n<\/div>\n
Being bitten on the nose by an eel certainly qualifies as a frightening experience! The fear this man is experiencing produces the same physiological responses in most people\u00a0\u2014\u00a0racing heart, rapid breathing, clammy hands. These and other fight-or-flight responses<\/a>\u00a0prepare the body to either defend itself or run away from danger. Why does fear elicit these changes in the body? The responses occur in large part because of hormones secreted by the adrenal glands.<\/p>\n
\nIntroduction to the Adrenal Glands<\/h1>\n<\/div>\n
Figure 9.6.2 Each of the two adrenal glands is found above a kidney.<\/em><\/figcaption><\/figure>\n The\u00a0adrenal glands<\/a><\/strong> are endocrine glands that produce a variety of hormones. Adrenal hormones include the fight-or-flight hormone adrenaline and the steroid hormone cortisol. The two adrenal glands are located on both sides of the body, just above the kidneys, as shown in Figure 9.6.2. The right adrenal gland (on the left in the figure) is smaller and has a pyramidal shape. The left adrenal gland (on the right in the figure) is larger and has a half-moon shape.<\/p>\n
Each adrenal gland has two distinct parts, and each part has a different function, although both parts produce hormones. There is an outer layer, called the adrenal cortex, which produces steroid hormones including cortisol. There is also an inner layer, called the adrenal medulla, which produces non-steroid hormones including adrenaline.<\/p>\n
\nAdrenal Cortex<\/h1>\n<\/div>\n
The\u00a0adrenal cortex<\/a>,<\/strong> or outer layer of the adrenal gland, is divided into three additional layers, called zones (see Figure 9.6.3). Each zone has distinct enzymes that produce different hormones from the common precursor molecule cholesterol, which is a lipid.<\/p>\n
- \n
- Zona glomerulosa<\/a><\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\n
- Zona fasciculata<\/a><\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\n
- Zona reticularis<\/a><\/strong>\u00a0is the innermost layer of the adrenal cortex. It is directly adjacent to the medulla of the adrenal gland.<\/li>\n<\/ol>\n
Figure 9.6.3 The adrenal cortex is divided into the three zones shown here. Each zone produces a different type of steroid hormone. This photomicrograph also shows the medulla of the adrenal gland.<\/em><\/figcaption><\/figure>\n <\/p>\n
\nTypes of Adrenal Cortex Hormones<\/span><\/p>\n<\/div>\n
Hormones produced by the adrenal cortex are\u00a0known\u00a0by the general term\u00a0corticosteroids<\/a>.<\/strong> As steroid hormones<\/a>, corticosteroids are endocrine hormones that are made of lipids<\/a> and exert their effects on target cells<\/a> by crossing the plasma membrane<\/a> and binding with receptors within the cytoplasm. A steroid hormone and its receptor form a complex that enters the cell nucleus<\/a> and affects gene expression<\/a>. There are three types of corticosteroids synthesized and secreted by the adrenal cortex. Each type is produced by a different zone of the adrenal cortex, as shown in Figure 9.6.4.<\/p>\n
Figure 9.6.4 The three zones of the adrenal cortex \u2014 as well as the adrenal medulla \u2014 are each associated with a specific type of hormone.<\/em><\/figcaption><\/figure>\n Mineralocorticoids<\/h3>\n
Mineralocorticoids are produced in the zona glomerulosa<\/a> and include the hormone aldosterone<\/a>. These hormones help control the balance of mineral salts (electrolytes) in the body. In the kidneys, aldosterone increases the reabsorption of sodium ions and the excretion of potassium ions. Aldosterone also stimulates the retention of sodium ions by cells in the colon and by the sweat glands. The amount of sodium in the body affects the volume of extracellular fluids (including the blood) and thereby affects blood pressure. In this way, mineralocorticoids help control blood volume and blood pressure.<\/p>\n
Glucocorticoids<\/h3>\n
Glucocorticoids are produced in the zona fasciculata<\/a> and include the hormone\u00a0cortisol<\/a>,\u00a0which is released in repsonse to stress and is considered the primary stress hormone. Glucocorticoids\u00a0help control the rate of metabolism of proteins<\/a>, fats, and sugars. In general, they increase the level of glucose<\/a> and fatty acids<\/a> circulating in the blood. Cells rely primarily on glucose for energy, but they can also use fatty acids for energy as an alternative to glucose. Glucocorticoids are also involved in suppression of the immune system, having a potent anti-inflammatory effect. In addition, cortisol reduces the production of new bone and decreases absorption of calcium from the gastrointestinal tract.<\/p>\n
Androgens<\/h3>\n
Androgens<\/a><\/strong>\u00a0are produced in the zona reticularis<\/a> and include the hormone DHEA (dehydroepiandrosterone). Androgens are a general term for male sex hormones, although this is somewhat misleading, as adrenal cortex androgens are produced by both males and females. In adult males, they are converted to more potent androgens, such as testosterone<\/a> in the male gonads (testes<\/a>). In adult females, they are converted to female sex hormones called estrogens<\/a>\u00a0in the female gonads (ovaries<\/a>).<\/p>\n
Regulation of Adrenal Cortex Hormones<\/h2>\n
Steroid hormone<\/a> production by the three zones of the adrenal cortex is regulated by hormones secreted by the anterior<\/a> lobe of the pituitary gland, as well as by other physiological stimuli. For example, the production of glucocorticoids such as cortisol is stimulated by adrenocorticotropic hormone (ACTH) from the anterior pituitary, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. When levels of glucocorticoids start to rise too high, they provide negative feedback<\/a> to the hypothalamus<\/a> and pituitary gland to stop secreting CRH and ACTH, respectively. This negative feedback mechanism is illustrated in Figure 9.6.5. The opposite occurs when levels of glucocorticoids start to fall too low.<\/p>\n
Figure 9.6.5 The negative feedback loop that controls production of glucocorticoids includes the pituitary gland and hypothalamus, in addition to the adrenal cortex.<\/em><\/figcaption><\/figure>\n \nAdrenal Medulla<\/h1>\n<\/div>\n
The\u00a0adrenal medulla<\/a><\/strong>\u00a0is at the center of each adrenal gland and is surrounded by the adrenal cortex. It contains a dense network of blood vessels into which it secretes its hormones. The hormones synthesized and secreted by the adrenal medulla are\u00a0generally known as\u00a0catecholamines<\/a><\/strong>, and they include\u00a0adrenaline<\/a><\/strong>\u00a0(also called epinephrine) and noradrenaline<\/a> (also called norepinephrine). These water-soluble, non-steroid hormones<\/a>\u00a0are made of amino acids<\/a>. As non-steroid hormones, they cannot cross the plasma membrane<\/a> of target cells<\/a>. Instead, they exert their effects by binding to receptors on the surface of target cells. The binding of hormone and receptor activates an enzyme in the plasma membrane that controls a second messenger. It is the second messenger that influences processes inside the cell.<\/p>\n
Catecholamines function to produce a rapid response throughout the body in stressful situations. They bring about such changes as increased heart rate, more rapid breathing, constriction of blood vessels in certain parts of the body, and an increase in blood pressure. The release of catecholamines by the adrenal medulla is stimulated by activation of the sympathetic division<\/a> of the autonomic nervous system<\/a>.<\/p>\n
\nDisorders of the Adrenal Glands<\/h1>\n<\/div>\n
Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The underlying cause of the abnormal secretion may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Both adrenal and pituitary glands are subject to the formation of tumors, which may cause adrenal disorders. The adrenal gland may also be affected by infections or autoimmune diseases.<\/p>\n
Adrenal Hypersecretion: Cushing\u2019s Syndrome<\/h2>\n
Hypersecretion of the glucocorticoid hormone cortisol<\/a> leads to a disorder\u00a0called\u00a0Cushing\u2019s syndrome<\/a>.<\/strong> The most common cause of Cushing\u2019s syndrome is a pituitary tumor, which causes excessive production of ACTH. The disease produces a wide variety of signs and symptoms, which may include obesity, diabetes, high blood pressure (hypertension), excessive body hair, osteoporosis, and depression. A distinctive sign of Cushing\u2019s syndrome is the appearance of stretch marks in the skin, as the skin becomes progressively thinner. Another distinctive sign is a moon face, in which fat deposits give the face a rounded appearance. Treatment of Cushing\u2019s syndrome depends on its cause and may include surgery to remove a tumor or medications to suppress activity of the adrenal glands.<\/p>\n
Adrenal Hyposecretion: Addison\u2019s Disease<\/h2>\n
Figure 9.6.6 Hyperpigmentation of the skin is a characteristic sign of Addison\u2019s disease. The photo on the left shows the dark skin pigmentation of an Addison\u2019s patient before treatment. The photo on the right shows the same patient after treatment.<\/em><\/figcaption><\/figure>\n Hyposecretion of the glucocorticoid hormone cortisol leads to a disorder\u00a0called\u00a0Addison\u2019s disease<\/a>.<\/strong> There may also be hyposecretion of mineralocorticoids with this disorder. Addison\u2019s disease is generally an autoimmune disorder, in which the immune system produces abnormal antibodies that attack cells of the adrenal cortex. Untreated infections, especially of tuberculosis, may also damage the adrenal cortex and cause Addison\u2019s disease. A third possible cause is decreased output of ACTH by the pituitary gland, generally due to a pituitary tumor. A distinctive sign of Addison\u2019s disease is hyperpigmentation of the skin (see the photos in Figure 9.6.6). Other symptoms tend to be nonspecific and include excessive fatigue. Addison\u2019s disease is generally treated with replacement hormones in pill form.<\/p>\n
\nFeature: My Human Body<\/h1>\n<\/div>\n
Figure 9.6.7\u00a0 BASE jumping is the <\/em>high point in this adrenaline “junkie’s” day!\u00a0<\/em><\/figcaption><\/figure>\n Does just\u00a0looking<\/em> at this photo (Figure 9.6.7) cause you to break out in a cold sweat and experience heart palpitations? Imagine how scary it would be to actually<\/em>\u00a0fling yourself backward off a tall building like the BASE jumper in the photo! There would be very little time to use a parachute to slow your fall before you hit the ground. BASE jumping is called the most dangerous sport on Earth. In fact, it is so dangerous that it is outlawed in some places.<\/p>\n
People who participate in such dangerous activities as BASE jumping are likely to be adrenaline \u201cjunkies.\u201d They are addicted to the adrenaline rush and euphoria \u2014 or \u201chigh\u201d \u2014 it causes when their fight-or-flight response is triggered by danger. Why does adrenaline have this effect? Adrenaline is closely related to dopamine, a chemical messenger in the brain that plays a major role in pleasure and addiction.<\/p>\n
Adrenaline addicts don\u2019t have to participate in BASE jumping or other dangerous sports to get an adrenaline rush. They might choose a dangerous occupation like firefighting, participate in risky behaviors like reckless driving or bank robbing, or just pick fights with other people. They might even create their own stress by always taking on too much work or delaying projects until close to their deadline.<\/p>\n
While some excitement in one\u2019s life is generally a good thing, always putting oneself in danger or constantly being under stress are obviously not good things. If you think you might be an adrenaline addict, note that there are healthier ways to experience a hormonal \u201chigh.\u201d Running, biking, or participating in some other form of vigorous aerobic exercise causes the pituitary gland and hypothalamus to produce opiate-like endorphins, leading to a so-called \u201crunner\u2019s high.\u201d Like the euphoric feeling adrenaline causes, a runner\u2019s high may last for hours.<\/p>\n
\n\n\n 9.6 Summary<\/span><\/h1>\n<\/header>\n
\n- \n
- The adrenal glands<\/a>\u00a0are endocrine glands that produce a variety of hormones. The two adrenal glands are located on both sides of the body, just above the kidneys. Each gland has two layers: an outer layer called the adrenal cortex<\/a> and an inner layer called the adrenal medulla<\/a>.<\/li>\n
- The adrenal cortex produces steroid hormones called by the general term corticosteroids<\/a>, of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and androgens<\/a>\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\n
- The adrenal medulla produces non-steroid catecholamine hormones, including adrenaline<\/a> and noradrenaline<\/a>. These hormones stimulate the fight-or-flight response<\/a>.<\/li>\n
- Disorders of the adrenal glands generally include either hypersecretion<\/a> or hyposecretion<\/a> of adrenal hormones. The cause may be a problem with the adrenal glands or with the pituitary gland, which controls adrenal cortex hormone production. Examples include Cushing\u2019s syndrome<\/a>, in which there is hypersecretion of cortisol, and Addison\u2019s disease<\/a>, in which there is hyposecretion of cortisol and mineralocorticoids.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n
\n\n 9.6 Review Questions<\/span><\/h1>\n<\/header>\n
\n- \n
- Describe the structure and location of the adrenal glands.<\/li>\n
- \n\n
- The adrenal cortex produces steroid hormones called by the general term corticosteroids<\/a>, of which there are three types: mineralocorticoids (such as aldosterone), which helps control electrolyte balance; glucocorticoids (such as cortisol), which helps control the rate of metabolism, suppresses the immune system, and is the major stress hormone; and androgens<\/a>\u00a0(such as DHEA), which is converted to sex hormones in the gonads.<\/li>\n
- Zona fasciculata<\/a><\/strong> is the middle layer of the adrenal cortex. It is the largest of the three zones, accounting for nearly 80 per cent of the adrenal cortex.<\/li>\n
- Zona glomerulosa<\/a><\/strong>\u00a0is the outermost layer of the adrenal cortex. It lies immediately under the outer fibrous capsule that encloses the adrenal gland.<\/li>\n
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