Passage The Adrenal Glands Are Divided into Two Anatomically Distinct Regions

Passage
The adrenal glands are divided into two anatomically distinct regions, the adrenal medulla and the adrenal cortex.  The adrenal medulla is a collection of irregularly shaped cells located in the interior portion of each adrenal gland.  In response to changing serum levels of corticosteroid hormones, medullary cells synthesize and secrete the catecholamines norepinephrine and epinephrine.  Norepinephrine and epinephrine are water-soluble compounds, and their actual secretion into the bloodstream is stimulated by acetylcholine (ACh) -mediated signaling in the sympathetic component of the autonomic nervous system.  Figure 1 shows the enzyme-mediated synthesis of norepinephrine and epinephrine.
Figure 1The adrenal cortex is the outer portion of the adrenal gland and is composed of cells that synthesize and secrete lipophilic hormones derived from cholesterol.  Hormones produced by the adrenal cortex include the principal glucocorticoid hormone (cortisol) and the mineralocorticoid hormone (aldosterone) .The hypothalamus and pituitary gland regulate and control the endocrine functions of the adrenal cortex (Figure 2) .  Secretion of corticotrophin-releasing hormone (CRH) from the hypothalamus promotes the synthesis and release of adrenocorticotrophic hormone (ACTH) by the pituitary gland.  ACTH acts on adrenal cortex cells to promote the growth of cortical tissue and to increase the synthesis and secretion of glucocorticoids.  In addition to its body-wide functions as the principal stress hormone, cortisol also regulates adrenal activity by inhibiting CRH release from the hypothalamus and ACTH release from the pituitary.
Figure 2
-For individuals who exhibit insufficient hormone production by the adrenal cortex, ACTH is sometimes administered as a treatment option.  Clinicians have reported that most patients fail to respond to this treatment with ACTH.  The most likely reason for this outcome is that nonresponsive patients:

A) release insufficient amounts of ACTH from the pituitary gland.
B) continuously overexpress the genes for DBH and PNMT.
C) exhibit impaired cholesterol synthesis in the smooth endoplasmic reticulum of adrenocortical cells.
D) express an overactive ACTH receptor on cells responsive to cortisol.

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