Nokea
Thyroid hormone (a small iodinated amine) enters target cells in a manner similar to ________.
- A. insulin, because insulin is a small peptide
- B. steroid hormones, because both diffuse easily into target cells
- C. growth hormone, because the thyroid works synergistically with thyroid hormone
- D. glucagon, because the structure of glucagon is similar to that of thyroid hormone
Correct Answer: B
Rationale: The correct answer is B: steroid hormones, because both diffuse easily into target cells. Thyroid hormone, being a small iodinated amine, can easily pass through the cell membrane and bind to intracellular receptors, similar to steroid hormones. Unlike insulin (choice A), which binds to cell surface receptors, thyroid hormone and steroid hormones enter the cell to exert their effects. Growth hormone (choice C) and glucagon (choice D) do not share the same mechanism of entry into target cells as thyroid hormone, making them incorrect choices.
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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.
A 32-year-old woman presents with a blood pressure of 155/96 mm Hg. In response to questioning, she admits that she loves licorice and eats some at least three times a week. She probably has a low level of
- A. type 2 11β-hydroxysteroid dehydrogenase activity
- B. ACTH
- C. 11β-hydroxylase activity
- D. glucocorticoid transferase
Correct Answer: A
Rationale: The correct answer is A: type 2 11β-hydroxysteroid dehydrogenase activity. Licorice contains glycyrrhizin, which inhibits this enzyme, leading to increased levels of cortisol and mineralocorticoids. This explains the elevated blood pressure in the patient. Choice B, ACTH, is incorrect because licorice consumption does not directly affect ACTH levels. Choice C, 11β-hydroxylase activity, is incorrect as licorice does not impact this enzyme directly. Choice D, glucocorticoid transferase, is also incorrect as licorice does not affect this enzyme's activity.
Which of the following sympathomimetics is not a catecholamine:
- A. Adrenaline
- B. Noradrenaline
- C. Amphetamine
- D. Isoprenaline
Correct Answer: C
Rationale: The correct answer is C: Amphetamine. Amphetamine is not a catecholamine because it is a synthetic drug, not naturally produced by the body like adrenaline (A), noradrenaline (B), and isoprenaline (D). Catecholamines are a class of neurotransmitters that include dopamine, adrenaline, and noradrenaline, all of which have a catechol group in their chemical structure. Amphetamine, on the other hand, is a substituted phenethylamine with no catechol group. This distinction makes amphetamine the only non-catecholamine among the given options.
The rate of metabolism of all body cells is regulated by _______.
- A. parathyroid hormone
- B. aldosterone
- C. calcitonin
- D. thyroid hormone
Correct Answer: D
Rationale: The correct answer is D: thyroid hormone. Thyroid hormone plays a crucial role in regulating the rate of metabolism in all body cells by influencing the production of enzymes involved in energy production. It increases the body's metabolic rate, affecting processes such as heart rate, temperature regulation, and energy expenditure. Parathyroid hormone (A) regulates calcium levels, aldosterone (B) regulates electrolyte balance, and calcitonin (C) regulates calcium metabolism, but they do not directly influence overall metabolism rate in all body cells. Thyroid hormone is the primary hormone responsible for controlling metabolism throughout the body.