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Adrenal Cortex: Hormone Regulation and Action

Adrenal Gland
Endocrine System
Systems Biology

Systems Biology

The adrenal glands are responsible for producing a multitude of hormones that regulate various processes such as blood pressure, stress responses, the immune system, and sexual development. The adrenal gland consists of two distinct parts: the adrenal cortex and the adrenal medulla. The adrenal cortex is divided into three regions, each responsible for secreting different corticosteroid hormones: the zona glomerulosa produces mineralocorticoid hormones like aldosterone in response to low blood pressure; the zona fasciculata produces glucocorticoids such as cortisol in response to stress; and the zona reticularis produces adrenal androgens, which can be converted into more potent sex hormones in peripheral tissues.

Aldosterone increases sodium and water reabsorption, raising blood pressure, and stimulates the excretion of hydrogen ions and potassium, preventing the blood from becoming too acidic or high in potassium. Cortisol raises blood glucose levels through protein catabolism and gluconeogenesis, and reduces inflammation and other immune responses. Finally, adrenal androgens are converted into stronger sex hormones like testosterone, dihydrotestosterone (DHT), and estrogens, which drive sexual development and sexual health.

Lesson Outline

<ul> <li>Introduction to the adrenal glands and adrenal cortex <ul> <li>Adrenal gland consists of two parts: adrenal cortex and adrenal medulla</li> <li>Adrenal cortex is derived from the mesoderm, the middle germ layer during embryonic development</li> </ul> </li> <li>Three regions of the adrenal cortex <ul> <li>Zona glomerulosa (outermost layer)</li> <li>Zona fasciculata (middle layer)</li> <li>Zona reticularis (innermost layer)</li> </ul> </li> <li>Zona glomerulosa and mineralocorticoid hormones (e.g., aldosterone) <ul> <li>Responsible for regulating salt, water, and blood pressure</li> <li>Primary mineralocorticoid hormone: aldosterone</li> <li>Produced in response to low blood pressure via the renin-angiotensin-aldosterone system (RAAS)</li> <li>Actions of aldosterone <ul> <li>Increases reabsorption of sodium and water</li> <li>Raises blood pressure</li> <li>Stimulates excretion of hydrogen ions and potassium</li> </ul> </li> </ul> </li> <li>Zona fasciculata and glucocorticoid hormones (e.g., cortisol) <ul> <li>Secreted in response to stress</li> <li>Two main glucocorticoids: cortisol and cortisone</li> <li>Pathway to cortisol production <ul> <li>Hypothalamus releases corticotropin-releasing factor (CRF)</li> <li>CRF stimulates secretion of adrenocorticotropic hormone (ACTH) from the anterior pituitary</li> <li>ACTH acts on zona fasciculata to secrete cortisol</li> </ul> </li> <li>Actions of cortisol <ul> <li>Increases blood glucose levels through gluconeogenesis</li> <li>Increases breakdown of proteins to generate amino acids for gluconeogenesis</li> <li>Dampens inflammation and other immune responses during acute stress</li> </ul> </li> </ul> </li> <li>Zona reticularis and sex hormones (e.g., androgens) <ul> <li>Responsible for sexual development and sexual health</li> <li>Produces a small amount of androgens</li> <li>Androgens can be converted into stronger sex hormones in peripheral tissues <ul> <li>Examples: testosterone, dihydrotestosterone (DHT), and estrogens</li> </ul>

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What is the primary function of the adrenal cortex?

The primary function of the adrenal cortex is to produce and secrete corticosteroid hormones, which maintain homeostasis by regulating various physiologic processes (e.g, metabolism, stress responses, electrolyte balance). The adrenal cortex is divided into three distinct zones: the zona glomerulosa, zona fasciculata, and zona reticularis, each responsible for producing specific types of corticosteroid hormones.

How are the adrenal cortex and adrenal medulla different in terms of their hormonal secretions?

The adrenal cortex and adrenal medulla are two distinct regions within the adrenal glands with different hormonal secretions. The adrenal cortex produces corticosteroid hormones, which include mineralocorticoid hormones like aldosterone, glucocorticoids like cortisol, and sex hormones like adrogens. On the other hand, the adrenal medulla primarily secretes catecholamines, such as adrenaline (epinephrine) and noradrenaline (norepinephrine), both of which play crucial roles in the body's fight-or-flight response to stress.

In which zone of the adrenal cortex are mineralocorticoid hormones, such as aldosterone, produced?

Mineralocorticoid hormones, including aldosterone, are mainly produced in the zona glomerulosa, which is the outermost layer of the adrenal cortex. Aldosterone plays a vital role in the regulation of blood pressure through the control of sodium and potassium levels in the blood and the modulation of fluid balance.

Which zone of the adrenal cortex is responsible for producing glucocorticoids, and what are their primary functions?

The zona fasciculata, the middle and largest layer of the adrenal cortex, is responsible for producing glucocorticoids, (e.g., cortisol). These hormones play essential roles in regulating metabolism, immune response, and the body's ability to cope with stress. They also have potent anti-inflammatory and immunosuppressive effects, which help the body maintain homeostasis during times of stress or illness.

What specific hormones are secreted by the zona reticularis, and what are their functions?

The zona reticularis, the innermost layer of the adrenal cortex, mainly produces androgens like dehydroepiandrosterone (DHEA) and androstenedione. These hormones serve as precursors for the synthesis of sex hormones, such as testosterone and estrogen, both within the adrenal glands and in other tissues throughout the body. Androgens produced by the zona reticularis contribute to the development of secondary sexual characteristics and the maintenance of normal reproductive function.