Question 1

Exercise increases catecholamine release.Stimulation of $\alpha$-adrenergic receptors specifically leads to:&#10;A)An increase in insulin secretion.&#10;B)Vasodilation of skeletal muscle arterioles.&#10;C)Vasoconstriction of splanchnic arterioles.&#10;D)Vasodilation of veins and lymphatic vessels.&#10;E)A positive inotropic effect on cardiac function.

Accepted Answer

Stimulation of $\alpha$-adrenergic receptors typically causes vasoconstriction, particularly in splanchnic arterioles, which helps redirect blood flow to essential areas during exercise.

Question 2

Cortisol is considered a &#34;stress hormone.&#34; One of its direct actions that help an individual survive a physiological stress (e.g.,surgery)is:&#10;A)To increase hepatic gluconeogenesis.&#10;B)To increase skeletal muscle protein synthesis.&#10;C)To increase hepatic lipogenesis.&#10;D)To decrease adipose tissue lipolysis.&#10;E)To increase hepatic glycolysis.

Accepted Answer

Cortisol increases hepatic gluconeogenesis, which means it promotes the conversion of non-carbohydrate sources such as amino acids and fatty acids to glucose. This is important during times of stress, as glucose is the primary energy source for the body, and cortisol helps ensure that there is enough glucose available to meet the body's demands.

Question 3

ACTH has rapid,intermediate,and longer term effects on the function of the zona fasciculata.Which of the following is a target of rapid effects?&#10;A)Adrenal hypertrophy.&#10;B)Cortisol secretion.&#10;C)Steroidogenic acute regulatory (StAR)protein activation.&#10;D)CYP21A2 expression.&#10;E)Low-density lipoprotein (LDL)receptor expression.

Accepted Answer

The rapid effects of ACTH on the zona fasciculata include the activation of the Steroidogenic acute regulatory (StAR) protein, which facilitates the transport of cholesterol into the mitochondria for steroidogenesis.

Question 4

The zona glomerulosa is notable for its absence of the following enzyme:&#10;A)CYP17&#10;B)CYP11B2&#10;C)CYP21A2&#10;D)CYP11A1&#10;E)3&#946;-Hydroxysteroid dehydrogenase (3$\beta$ HSD)

Accepted Answer

The zona glomerulosa, the outermost layer of the adrenal cortex, lacks the enzyme CYP17. This enzyme is essential for the synthesis of glucocorticoids and sex steroids but not for the production of mineralocorticoids, which are the primary products of the zona glomerulosa.

Question 5

Cortisol can bind to both the glucocorticoid receptor and the mineralocorticoid receptor.In the cells of the distal nephron,cortisol is prevented from binding to the mineralocorticoid receptor by:&#10;A)Competitive inhibition by aldosterone.&#10;B)Glucuronide conjugation.&#10;C)Conversion to cortisone.&#10;D)Rapid excretion.&#10;E)Binding to heat shock chaperone proteins.

Accepted Answer

Cortisol is prevented from binding to the mineralocorticoid receptor in the cells of the distal nephron by being converted to cortisone, which has a much lower affinity for the mineralocorticoid receptor. This conversion is catalyzed by the enzyme 11β-hydroxysteroid dehydrogenase type 2.

Question 6

A 25-year-old woman sees her physician because of hirsutism (inappropriate hair growth)and excessive acne.During examination,her blood pressure is 150/90 mm Hg (elevated).Blood work reveals normal Na⁺ but low/normal K⁺ levels.Testosterone and dihydrotestosterone (DHT)levels are in the high end of the normal range,and levelso f DHEAS and ACTH are moderately elevated.Her physician suspects late-onset congenital adrenal hyperplasia resulting from subnormal activity of an adrenal enzyme.The "hyperplasia" associated with congenital adrenal hyperplasia is caused by elevated levels of:

A)DHEAS.
B)Cortisol.
C)ACTH.
D)Aldosterone.
E)Deoxycorticosterone (DOC).

Accepted Answer

The elevated levels of ACTH in this patient indicate that there is excessive stimulation of the adrenal gland, which can lead to hyperplasia. This excessive stimulation is due to subnormal activity of an adrenal enzyme, which is causing the high testosterone and DHT levels. Elevated levels of DHEAS are seen in some forms of congenital adrenal hyperplasia, but in this case, the DHEAS levels are only moderately elevated. Cortisol and aldosterone levels are normal in this patient. Deoxycorticosterone (DOC) is not typically elevated in congenital adrenal hyperplasia.

Question 7

A patient has been receiving immunosuppressive doses of glucocorticoids for 6 months.At the end of this therapy,the dosage of the hormone must be slowly tapered down over a period of weeks.This is because of the development of:

A)Adrenal atrophy.
B)Pituitary hypertrophy.
C)Upregulation of glucocorticoid receptors.
D)Elevated ACTH levels.
E)Increased levels of circulating cortisol-binding globulin (CBG).

Accepted Answer

Prolonged administration of exogenous glucocorticoids results in hypothalamic-pituitary-adrenal (HPA) axis suppression. As a result of this suppression, the adrenal glands may atrophy and lose the ability to produce endogenous glucocorticoids. Therefore, when glucocorticoid therapy is discontinued, a gradual tapering of the dose is necessary to allow the adrenal glands to gradually recover and resume endogenous glucocorticoid production. Abruptly stopping glucocorticoid therapy can result in acute adrenal insufficiency, which can be life-threatening.

Question 8

The adrenal medulla synthesizes catecholamines.The first enzyme in the catecholamine synthesis pathway,tyrosine hydroxylase,is stimulated by:&#10;A)Cortisol.&#10;B)Epinephrine.&#10;C)Norepinephrine.&#10;D)Acetylcholine.&#10;E)Nitric oxide.

Accepted Answer

Tyrosine hydroxylase, the first enzyme in the catecholamine synthesis pathway, is stimulated by acetylcholine. This occurs in the adrenal medulla, where acetylcholine acts as a neurotransmitter to initiate the synthesis of catecholamines such as epinephrine and norepinephrine.

Question 9

Cushing's disease is caused by an ACTH-oversecreting pituitary tumor.One of the effects of this is:&#10;A)Increased skeletal muscle mass.&#10;B)Decreased catecholamine responsiveness in the heart.&#10;C)Anorexia.&#10;D)Insulin resistance.&#10;E)Decreased glucagon responsiveness in adipose tissue.

Accepted Answer

Cushing's disease leads to excess cortisol secretion which can cause insulin resistance. This is because cortisol opposes the action of insulin and can lead to impaired glucose uptake and utilization by cells.

Question 10

A 25-year-old woman sees her physician because of hirsutism (inappropriate hair growth)and excessive acne.During examination,her blood pressure is 150/90 mm Hg (elevated).Blood work reveals normal Na⁺ levels but low/normal K⁺ levels.Testosterone and dihydrotestosterone (DHT)levels are in the high end of the normal range,and the levels of dehydroepiandrosterone sulfate (DHEAS)and adrenocorticotropic hormone (ACTH)are moderately elevated.Her physician suspects late-onset congenital adrenal hyperplasia resulting from subnormal activity of an adrenal enzyme.The subnormal activity of which enzyme explains both the elevated adrenal androgens (e.g.,DHEAS)and hypertension (elevated blood pressure)?

A)CYP11B1
B)CYP17
C)CYP21A2
D)CYP11B2
E)CYP11A1

Accepted Answer

CYP11B1 deficiency leads to accumulation of 11-deoxycorticosterone, causing hypertension, and increased production of adrenal androgens, explaining the hirsutism and acne.

Deck 43: The Adrenal Glands