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
-Administration of a drug causes increased secretion of norepinephrine and epinephrine by the adrenal medulla. This most probably occurs because the drug:

Question

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
-Administration of a drug causes increased secretion of norepinephrine and epinephrine by the adrenal medulla. This most probably occurs because the drug:

Quizplus · Accepted Answer

11ecba2d_0ffd_5cc8_a3bf_4b6ec0107190_MD0008_00 The autonomic nervous system refers to the collection of neurons and peripheral nerves that regulate the involuntary functions of smooth muscles, cardiac muscles, and endocrine organs. The autonomic nervous system is composed of two branches with broadly antagonistic effects: the sympathetic nervous system and the parasympathetic nervous system. Many tissues innervated by the autonomic nervous system are innervated by both branches. Innervation of the adrenal medulla by the autonomic nervous system is unique in that the adrenal medulla is only innervated by the sympathetic nervous system. The passage states that norepinephrine and epinephrine release is stimulated by ACh-mediated signaling in the sympathetic component of the autonomic nervous system. Accordingly, for a drug to trigger an increased secretion of norepinephrine and epinephrine by the adrenal medulla, the drug must generate effects that mimic the activity of the sympathetic nervous system. (Choice A) Figure 2 in the passage shows that ACTH is released by the pituitary gland. ACTH release generally stimulates secretion of glucocorticoids and mineralocorticoids from the adrenal cortex. However, ACTH release does not affect the secretion of epinephrine or norepinephrine from the adrenal medulla, which is only stimulated by activation of sympathetic motor fibers. (Choice B) Figure 1 shows that the enzymes TH and AADC catalyze the precursors to norepinephrine and epinephrine. Consequently, if these enzymes were inhibited, there would be a decrease (not increase) in norepinephrine and epinephrine levels. (Choice D) According to Figure 1, norepinephrine and epinephrine are derived from the amino acid L-tyrosine. A drug that activates enzymes that mediate the breakdown of tyrosine derivatives would degrade both norepinephrine and epinephrine. As a result, the secretion of norepinephrine and epinephrine would be decreased (not increased). Educational objective: The autonomic nervous system is divided into the parasympathetic and sympathetic divisions, which are generally antagonistic in function. Although most tissues are innervated by both sympathetic and parasympathetic motor fibers, the adrenal medulla is unique in that it is only innervated by the sympathetic nervous system.

Passage The Adrenal Glands Are Divided into Two Anatomically Distinct Regions