Nokea
When blood glucose levels are low, the ______ will increase the secretion of ______.
- A. adrenal cortex: aldosterone
- B. pancreas; glucagon
- C. pancreas: insulin
- D. posterior pituitary: ADH
Correct Answer: B
Rationale: The correct answer is B: pancreas; glucagon. When blood glucose levels are low, the pancreas secretes glucagon. Glucagon acts to increase blood glucose levels by stimulating the liver to release stored glucose. The adrenal cortex does not directly regulate blood glucose levels through aldosterone secretion. Insulin is secreted by the pancreas in response to high blood glucose levels to lower them, not increase them. The posterior pituitary secretes ADH to regulate water balance, not blood glucose levels.
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Thyroxine:
- A. is mostly bound to albumin in the plasma, since this has the largest capacity
- B. is 2-5 times more potent that triiodothyronine (T3)
- C. stimulates TSH release
- D. ∼33% is deiodinated in the liver to T3
Correct Answer: D
Rationale: The correct answer is D. Thyroxine is deiodinated in the liver to T3, so approximately 33% of thyroxine is converted to the more active form, triiodothyronine. This conversion is important for regulating metabolic processes in the body. Choices A and C are incorrect because thyroxine is primarily bound to thyroxine-binding globulin in the plasma, not albumin, and it does not stimulate TSH release. Choice B is incorrect because T3 is actually more potent than thyroxine, not the other way around.
The following statements concerning prazosin and phentolamine are correct EXCEPT:
- A. Both antagonize alpha1-receptors
- B. Both cause the same degree of tachycardia
- C. Both decrease blood pressure
- D. Both are competitive antagonists
Correct Answer: B
Rationale: Correct Answer: B
Rationale:
1. Prazosin and phentolamine both antagonize alpha1-receptors, leading to vasodilation and decreased blood pressure.
2. Both drugs are competitive antagonists, competing with norepinephrine at alpha1-receptors.
3. However, phentolamine causes reflex tachycardia due to its non-selective alpha-adrenergic blockade, unlike prazosin.
4. Therefore, the statement that both cause the same degree of tachycardia is incorrect based on their pharmacological differences.
The secretion of cortisol by the adrenal gland suppresses further secretion of ACTH by the anterior pituitary gland. What is this interaction called?
- A. Cerebral lateralization
- B. Circadian rhythm
- C. Cellular differentiation
- D. Negative feedback control
Correct Answer: D
Rationale: The correct answer is D: Negative feedback control. This interaction is a classic example of negative feedback control in the endocrine system. Cortisol inhibits the release of ACTH, which in turn reduces the stimulation of cortisol production, creating a feedback loop to maintain hormonal balance. Choice A, cerebral lateralization, refers to the specialization of brain function. Choice B, circadian rhythm, pertains to the 24-hour biological cycle. Choice C, cellular differentiation, involves the process of cells becoming specialized for specific functions. Thus, the correct answer is D because it accurately describes the feedback mechanism at play in the cortisol-ACTH interaction.
Cushing syndrome:
- A. may be caused by steroid (prednisone) therapy.
- B. is caused by adrenal insufficiency.
- C. is characterized by hypoglycemia and low blood volume.
- D. is treated with growth hormone.
Correct Answer: A
Rationale: The correct answer is A because Cushing syndrome is typically caused by prolonged exposure to high levels of cortisol, which can result from steroid therapy like prednisone. This leads to symptoms such as weight gain, high blood pressure, and muscle weakness. Adrenal insufficiency (B) is actually the opposite condition. Cushing syndrome is characterized by hyperglycemia and increased blood volume, making choices C incorrect. Growth hormone is not a primary treatment for Cushing syndrome, making choice D incorrect.
What stimulates the release of PTH from the parathyroid gland?
- A. TSH from the posterior pituitary gland
- B. high levels of calcium in the blood
- C. calcitonin from the anterior pituitary gland
- D. low levels of calcium in the blood
Correct Answer: D
Rationale: The correct answer is D: low levels of calcium in the blood. When calcium levels drop, the parathyroid gland releases parathyroid hormone (PTH) to increase calcium levels in the blood. This is a negative feedback mechanism to maintain calcium homeostasis. A: TSH from the posterior pituitary gland is incorrect because TSH is involved in regulating thyroid function, not PTH release. B: High levels of calcium in the blood would not stimulate PTH release as the body aims to lower, not raise, calcium levels. C: Calcitonin from the anterior pituitary gland is incorrect because calcitonin is released by the thyroid gland and works to lower blood calcium levels, opposing the action of PTH.