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Which gland secretes TSH, ACTH, and growth hormone?
- A. Neurohypophysis
- B. Pancreas
- C. Adrenal medulla
- D. Anterior pituitary gland
Correct Answer: D
Rationale: The correct answer is D, the anterior pituitary gland, because it secretes TSH, ACTH, and growth hormone. The anterior pituitary gland is also known as the adenohypophysis, and it plays a key role in regulating various bodily functions through the release of different hormones. The other choices are incorrect because the neurohypophysis (choice A) secretes hormones like oxytocin and vasopressin, the pancreas (choice B) secretes insulin and glucagon, and the adrenal medulla (choice C) secretes adrenaline and noradrenaline.
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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.
Your patient is diagnosed with myasthenia gravis, and she is given a prescription for pyridostigmine. Which of the following best summarizes the drug’s mechanism of action?
- A. Blocks muscarinic receptors, so that acetylcholine preferentially stimulates skeletal muscle
- B. Inhibits reuptake of acetylcholine by motor nerves
- C. Inhibits skeletal muscle activation at rest so that the muscles are less susceptible to fatigue during exercise
- D. Inhibits breakdown of acetylcholine, thereby improving activation of skeletal muscle by acetylcholine
Correct Answer: D
Rationale: The correct answer is D: "Inhibits breakdown of acetylcholine, thereby improving activation of skeletal muscle by acetylcholine."
Rationale:
1. Pyridostigmine is an acetylcholinesterase inhibitor, which means it blocks the breakdown of acetylcholine.
2. In myasthenia gravis, there is a decrease in acetylcholine receptor sites, leading to muscle weakness.
3. By inhibiting the breakdown of acetylcholine, pyridostigmine increases the availability of acetylcholine at the neuromuscular junction, improving muscle activation.
4. This mechanism helps alleviate muscle weakness in myasthenia gravis patients.
Summary:
A: Incorrect. Pyridostigmine does not block muscarinic receptors or change the preference of acetylcholine stimulation.
B: Incorrect. Pyridostigmine does not inhibit reuptake of acetylcholine; it acts by inhibiting its breakdown
The nurse reviews the function of thyroid gland hormones. What is the primary function of calcitonin?
- A. Sodium and potassium balance
- B. Magnesium balance
- C. Norepinephrine balance
- D. Calcium and phosphorus balance
Correct Answer: D
Rationale: The primary function of calcitonin is to regulate calcium and phosphorus balance in the body. Calcitonin works to decrease blood calcium levels by inhibiting bone breakdown and increasing calcium excretion by the kidneys. This helps maintain the overall balance of calcium and phosphorus in the body. Choices A, B, and C are incorrect as they do not align with the known function of calcitonin. Sodium and potassium balance, magnesium balance, and norepinephrine balance are not directly influenced by calcitonin.
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.
Which endocrine gland is known as the master gland?
- A. Adrenal
- B. Liver
- C. Pancreas
- D. Pituitary
Correct Answer: D
Rationale: The correct answer is D: Pituitary gland. The pituitary gland is known as the master gland because it controls the functions of other endocrine glands in the body by secreting various hormones that regulate growth, reproduction, metabolism, and other essential bodily functions. It is located at the base of the brain and plays a crucial role in maintaining hormonal balance.
Explanation for other choices:
A: Adrenal gland primarily regulates stress response and metabolism.
B: Liver is not an endocrine gland; it is involved in metabolism and detoxification.
C: Pancreas is responsible for regulating blood sugar levels through insulin and glucagon secretion but is not known as the master gland.