Nokea
Steroid hormones:
- A. require a second messenger.
- B. are secreted by the adrenal cortex.
- C. are secreted by the posterior pituitary.
- D. are secreted by the pancreas.
Correct Answer: B
Rationale: The correct answer is B: Steroid hormones are secreted by the adrenal cortex. The adrenal cortex is responsible for producing steroid hormones such as cortisol, aldosterone, and sex hormones. This is supported by the understanding of endocrine gland functions. Choices A, C, and D are incorrect because steroid hormones do not require a second messenger, are not secreted by the posterior pituitary, and are not secreted by the pancreas. Understanding the specific glands and their hormone production is crucial in selecting the correct answer.
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Selective beta2 stimulants frequently cause:
- A. Skeletal muscle tremors
- B. Tolerance
- C. Tachycardia
- D. All of the above
Correct Answer: D
Rationale: Selective beta2 stimulants typically cause skeletal muscle tremors due to their action on beta2 receptors in skeletal muscles. They can also lead to tolerance with prolonged use, requiring higher doses for the same effect. Additionally, they can cause tachycardia by stimulating beta2 receptors in the heart. Therefore, all of the above choices (A, B, and C) are correct.
The binding of a steroid hormone to its receptor would lead to the __________.
- A. transcription of the DNA for the gene that is 'turned on' by this event
- B. direct activation of second-messenger agents in the cell
- C. direct activation of enzymes in the cell
- D. formation of cAMP
Correct Answer: A
Rationale: The correct answer is A because the binding of a steroid hormone to its receptor triggers a series of events that ultimately lead to the transcription of DNA for the gene that is 'turned on'. This process involves the hormone-receptor complex entering the nucleus, binding to specific DNA sequences, recruiting transcription factors, and initiating gene expression.
Choice B is incorrect because steroid hormones do not typically use second messengers for signaling. Choice C is incorrect because while some hormones can activate enzymes indirectly, steroid hormones primarily act through gene transcription. Choice D is incorrect because cAMP is typically associated with signaling pathways involving non-steroid hormones like adrenaline.
As plasma levels of calcium decrease:
- A. insulin is secreted.
- B. the parathyroid glands secrete an osteoclastic hormone.
- C. the kidneys excrete calcium and phosphorus.
- D. calcitonin is secreted.
Correct Answer: B
Rationale: The correct answer is B because as plasma levels of calcium decrease, the parathyroid glands secrete an osteoclastic hormone called parathyroid hormone (PTH). PTH acts to increase calcium levels by stimulating the release of calcium from bones via osteoclasts. Insulin secretion (choice A) is not directly related to calcium levels. The kidneys excreting calcium and phosphorus (choice C) would further decrease calcium levels. Calcitonin (choice D) actually decreases blood calcium levels by inhibiting bone breakdown, so it is not secreted when calcium levels decrease.
The term catecholamine best describes drugs that are:
- A. Adrenergic receptor blockers
- B. Atropine-like in terms of their mechanisms and sites of action
- C. Classified like neostigmine and physostigmine
- D. Similar to adrenaline and noradrenaline in terms of structure and major pharmacologic properties
Correct Answer: D
Rationale: The correct answer is D because catecholamines are structurally similar to adrenaline and noradrenaline, sharing a catechol nucleus and amine group. This similarity allows them to exert similar pharmacologic effects such as increasing heart rate and blood pressure. Adrenergic receptor blockers (A) inhibit the action of catecholamines, atropine-like drugs (B) block muscarinic receptors, and neostigmine and physostigmine (C) are cholinesterase inhibitors, not catecholamines.
Steroid hormones influence cellular activities by __________.
- A. activating cyclic AMP located outside the cell
- B. binding to DNA and forming a gene-hormone complex
- C. activating G proteins
- D. using calcium ions as a second messenger
Correct Answer: B
Rationale: The correct answer is B because steroid hormones bind to DNA and form a gene-hormone complex, which then regulates gene expression. This directly influences cellular activities at the genetic level. Choices A, C, and D are incorrect because steroid hormones do not activate cyclic AMP, G proteins, or use calcium ions as second messengers for their cellular actions. Steroid hormones act through genomic mechanisms, not via the signaling pathways associated with choices A, C, and D.