Nokea
The primary role of the parathyroid gland is:
- A. To maintain metabolic homeostasis
- B. To regulate serum calcium levels
- C. To send hormonal signals to other endocrine glands
- D. To receive hormonal signals from the hypothalamus
Correct Answer: B
Rationale: The correct answer is B: To regulate serum calcium levels. The parathyroid gland secretes parathyroid hormone (PTH) to regulate calcium levels in the blood. PTH increases calcium levels by stimulating bone resorption, enhancing calcium absorption in the intestines, and promoting calcium reabsorption in the kidneys. Choices A, C, and D are incorrect because the primary function of the parathyroid gland is specifically related to calcium regulation, not general metabolic homeostasis, signaling to other glands, or receiving signals from the hypothalamus.
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Diabetes insipidus is caused due to deficiency of hormone:
- A. Insulin
- B. ADH
- C. Growth hormone
- D. Oxytocin
Correct Answer: B
Rationale: The correct answer is B: ADH (antidiuretic hormone). Diabetes insipidus is a condition characterized by excessive thirst and urination due to a deficiency of ADH, which regulates water balance in the body. Insulin (choice A) is related to diabetes mellitus, not diabetes insipidus. Growth hormone (choice C) and oxytocin (choice D) do not play a direct role in water balance regulation. Therefore, choice B is the most appropriate answer for this question.
The anterior pituitary gland receives hormone messages from the hypothalamus via ________.
- A. a capillary network
- B. neurons that extend from the hypothalamus to the pituitary
- C. Schwann cells
- D. both a and b
Correct Answer: A
Rationale: The correct answer is A: a capillary network. The hypothalamus secretes hormones into the capillary network called the hypothalamic-hypophyseal portal system. These hormones travel directly to the anterior pituitary gland to regulate the release of its own hormones. Choice B is incorrect because neurons do not directly connect the hypothalamus and pituitary gland. Choice C is incorrect because Schwann cells are involved in myelination of peripheral nerves, not hormone transport. Choice D is incorrect because although both options A and B involve communication between the hypothalamus and pituitary gland, it is specifically the capillary network that carries hormone messages in this case.
Which of the following hormones is released in response to a nerve impulse?
- A. ADH
- B. cortisol
- C. testosterone
- D. insulin
Correct Answer: A
Rationale: The correct answer is A: ADH (Antidiuretic Hormone). ADH is released in response to a nerve impulse to regulate water balance in the body by increasing water reabsorption in the kidneys. Nerve impulses trigger the release of ADH from the posterior pituitary gland. Cortisol (B) is released in response to stress, testosterone (C) is a sex hormone, and insulin (D) is released in response to high blood sugar levels, not nerve impulses.
Pro-opiomelanocortin (POMC) is a prohormone for __________.
- A. ACTH
- B. growth hormone
- C. thyroxin
- D. insulin
Correct Answer: A
Rationale: Rationale: POMC is processed into various peptide hormones, including adrenocorticotropic hormone (ACTH). ACTH is produced by the pituitary gland and stimulates the adrenal glands to release cortisol. This is why option A is correct. Growth hormone, thyroxin, and insulin are not derived from POMC, making options B, C, and D incorrect.
In relation to the molecular mechanism of action of sympathomimetics, the following is CORRECT:
- A. Beta receptor stimulation increases c-GMP
- B. Alpha 2 receptor stimulation stimulates adenyl cyclase
- C. Alpha 2 receptor stimulation increases c-AMP
- D. Alpha 1 receptor stimulation releases IP3 and DAG
Correct Answer: D
Rationale: The correct answer is D: Alpha 1 receptor stimulation releases IP3 and DAG. When alpha 1 receptors are stimulated by sympathomimetics, they activate G-proteins which then stimulate phospholipase C. Phospholipase C cleaves phosphatidylinositol 4,5-bisphosphate (PIP2) into inositol trisphosphate (IP3) and diacylglycerol (DAG). IP3 triggers the release of calcium from intracellular stores, leading to smooth muscle contraction, while DAG activates protein kinase C to initiate various cellular responses. Choices A, B, and C are incorrect because beta receptor stimulation increases cAMP, alpha 2 receptor stimulation inhibits adenyl cyclase leading to decreased cAMP levels, and alpha 2 receptor stimulation does not increase cAMP.