Nokea
In the adrenal medulla:
- A. epinephrine is formed by the hydroxylation and decarboxylation of tyrosine
- B. 10% of the cells are the epinephrine-secreting type
- C. plasma norepinephrine levels are generally unchanged after adrenalectomy
- D. catecholamine t1/2 is 10 minutes in the circulation
Correct Answer: C
Rationale: Rationale for Choice C: Plasma norepinephrine levels are generally unchanged after adrenalectomy in the adrenal medulla because norepinephrine is mainly produced by postganglionic sympathetic nerve endings rather than the adrenal medulla. Adrenalectomy removes the adrenal gland, which primarily secretes epinephrine, not norepinephrine. Therefore, plasma norepinephrine levels would not be significantly affected by adrenalectomy.
Summary of other choices:
A: Incorrect. Epinephrine is formed from norepinephrine, not tyrosine, through methylation and hydroxylation.
B: Incorrect. The majority of cells in the adrenal medulla are epinephrine-secreting cells, not just 10%.
D: Incorrect. The half-life of catecholamines in the circulation is very short, around 2 minutes, not 10 minutes.
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The beta cells of the islets of Langerhans:
- A. are the hormone-secreting cells of the adrenal cortex.
- B. are insulin-secreting pancreatic cells.
- C. secrete releasing hormones.
- D. secrete steroids.
Correct Answer: B
Rationale: The correct answer is B because beta cells of the islets of Langerhans are specialized pancreatic cells that secrete insulin, a hormone crucial for regulating blood sugar levels. Insulin helps cells absorb glucose from the bloodstream, lowering blood sugar levels. Choice A is incorrect because the hormone-secreting cells of the adrenal cortex are called adrenal cortical cells, not beta cells. Choice C is incorrect as releasing hormones are typically secreted by the hypothalamus to stimulate the pituitary gland. Choice D is incorrect because steroids are primarily secreted by the adrenal cortex, not the beta cells of the islets of Langerhans.
Which of the pairs of hormones BOTH increase blood sugar?
- A. insulin and glucagon
- B. growth hormone and insulin
- C. glucagon and epinephrine
- D. antidiuretic hormone and glucagon
Correct Answer: C
Rationale: The correct answer is C, glucagon and epinephrine. Glucagon stimulates the liver to release glucose into the bloodstream, increasing blood sugar levels. Epinephrine, also known as adrenaline, has a similar effect by promoting the breakdown of glycogen into glucose. Insulin (choice A) decreases blood sugar by promoting glucose uptake into cells. Growth hormone (choice B) mainly affects growth and metabolism but doesn't directly increase blood sugar. Antidiuretic hormone (choice D) regulates water balance and has no direct effect on blood sugar levels.
Two terms that are paired incorrectly are .
- A. cortisol-adrenal cortex
- B. androgens-adrenal cortex
- C. calcitonin-thyroid
- D. corticosteroid-adrenal medulla
Correct Answer: D
Rationale: The correct answer is D because corticosteroids are produced by the adrenal cortex, not the adrenal medulla. Cortisol is a type of corticosteroid, making choice A incorrect. Androgens are indeed produced by the adrenal cortex, making choice B correct. Calcitonin is produced by the thyroid, not the adrenal cortex, making choice C incorrect. Therefore, the only pair that is incorrect is corticosteroid and adrenal medulla.
Which group is incorrect?
- A. Hormones of the anterior pituitary gland: ACTH, prolactin, TSH, growth hormone
- B. Hormones of the posterior pituitary gland: ADH, oxytocin
- C. Steroids: cortisol, aldosterone, testosterone, epinephrine
- D. Secretions of the gonads: estrogen, progesterone, testosterone
Correct Answer: C
Rationale: The correct answer is C because epinephrine is not a steroid hormone. Steroids are synthesized from cholesterol and have a specific chemical structure, while epinephrine is a catecholamine. Cortisol, aldosterone, and testosterone are examples of steroid hormones, but epinephrine belongs to the class of catecholamines. Therefore, C is incorrect. A, B, and D are correct as they accurately list hormones produced by the anterior pituitary gland, posterior pituitary gland, and gonads respectively.
The most common second messengers for peptide hormones are ______ and _____.
- A. peptide hormones and calcium.
- B. calcium and glucose.
- C. cAMP and calcium.
- D. cAMP and sodium.
Correct Answer: C
Rationale: The correct answer is C: cAMP and calcium. Peptide hormones bind to their receptors on the cell surface, activating G-proteins which then trigger the production of cAMP as a second messenger. cAMP then further activates protein kinases to initiate various cellular responses. Calcium is also a common second messenger in peptide hormone signaling pathways, regulating processes like muscle contraction and gene expression. Choice A is incorrect because peptide hormones themselves are not second messengers. Choice B is incorrect as glucose is not a common second messenger for peptide hormones. Choice D is incorrect as sodium is not typically involved in peptide hormone signaling pathways.