A researcher is investigating factors affecting adrenal hormone synthesis and release. An intact adrenal gland is obtained from a donor cadaver, and a histologic section through the entire gland is shown below. Cells from a specific part of the gland, indicated by the arrow, are extracted for further analysis. These cells are most likely to be directly activated by which of the following substances?

Question

A researcher is investigating factors affecting adrenal hormone synthesis and release.  An intact adrenal gland is obtained from a donor cadaver, and a histologic section through the entire gland is shown below.  Cells from a specific part of the gland, indicated by the arrow, are extracted for further analysis.  These cells are most likely to be directly activated by which of the following substances?

Quizplus · Accepted Answer

11ec160b_378c_36f5_9249_b9282c5e20f0_MD0001_00 The adrenal gland is made up of an outer cortex (divided into 3 zones) and an inner medulla: The zona glomerulosa is the outermost zone of the cortex and is composed of cells arranged in rounded or arched clusters (glomus is Latin for ball) that secrete mineralocorticoid hormones (primarily aldosterone). The zona fasciculata is the middle zone and contains foamy-appearing cells in columns (fascis is Latin for bundle or stack) that secrete glucocorticoid hormones (primarily cortisol). The zona reticularis is the inner zone of the cortex and contains cells in anastomosing cords (rete is Latin for net) that secrete androgens. The adrenal medulla is sharply demarcated from the cortex and is composed of chromaffin cells with a deeply basophilic cytoplasm. Chromaffin cells are modified neuroendocrine cells derived from the neural crest. They are stimulated by acetylcholine released by sympathetic preganglionic neurons and secrete catecholamines (80% epinephrine, 20% norepinephrine) directly into the bloodstream to amplify sympathetic nervous system activity. (Choice B) ACTH stimulates secretion of glucocorticoid hormones from the zona fasciculata. Cortisol produced in response to ACTH increases activity of the adrenal medullary enzyme phenylethanolamine N-methyltransferase, which catalyzes the conversion of norepinephrine to epinephrine. ACTH therefore indirectly upregulates medullary epinephrine production, but does not directly control it. (Choice C) Aldosterone secretion from the zona glomerulosa is primarily regulated by angiotensin II and extracellular potassium levels. (Choice D) Epinephrine released by the adrenal medulla acts on adrenergic receptors in the heart, lungs, liver, and skeletal muscle to increase sympathetic tone and mediate the acute stress response. (Choice E) Most sympathetic postganglionic neurons release norepinephrine to activate adrenergic receptors on the target tissues. However, the preganglionic fibers innervating the adrenal medulla (and the postganglionic neurons innervating eccrine sweat glands) release acetylcholine. Educational objective: Chromaffin cells are modified neuroendocrine cells derived from the neural crest. Chromaffin cells in the adrenal medulla are stimulated by acetylcholine released by sympathetic preganglionic neurons and secrete catecholamines directly into the bloodstream to amplify sympathetic nervous system activity.

A Researcher Is Investigating Factors Affecting Adrenal Hormone Synthesis and Release