Nokea
Most hormones of the endocrine system are regulated by a:
- A. Negative feedback mechanism.
- B. Positive feedback mechanism.
- C. Hormone-receptor complex.
- D. Hormone-gene complex.
Correct Answer: A
Rationale: The correct answer is A: Negative feedback mechanism. This is because most hormones in the endocrine system are regulated by a negative feedback loop, where the release of a hormone is inhibited once a certain level of that hormone is reached in the body. This helps maintain homeostasis.
Incorrect choices:
B: Positive feedback mechanism - This is less common in hormone regulation as it leads to amplification of a response rather than maintaining balance.
C: Hormone-receptor complex - While hormones bind to receptors to exert their effects, this is not the primary mechanism of hormone regulation.
D: Hormone-gene complex - While hormones can affect gene expression, this is not the primary mechanism of hormone regulation in the endocrine system.
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Regarding fat metabolism, which statement is CORRECT?
- A. ketone bodies accumulate in DKA due to a lack of acetyl-CoA substrate
- B. fatty acids are transported in the plasma bound to lipoprotein complexes
- C. cholesterol is transported from extra-hepatic cells to the liver by high-density lipoproteins (HDLs) in the endogenous pathway
- D. eicosanoids are synthesised from cholesterol
Correct Answer: C
Rationale: The correct answer is C because cholesterol is transported from extra-hepatic cells to the liver by high-density lipoproteins (HDLs) in the endogenous pathway. HDLs are responsible for picking up excess cholesterol from peripheral tissues and transporting it back to the liver for excretion. This process helps regulate cholesterol levels in the body.
Explanation for other choices:
A: Ketone bodies accumulate in DKA due to increased fatty acid breakdown, not a lack of acetyl-CoA substrate.
B: Fatty acids are primarily transported in the bloodstream bound to albumin, not lipoprotein complexes.
D: Eicosanoids are derived from arachidonic acid, not cholesterol.
Identify a gland that is controlled by an anterior pituitary hormone.
- A. pancreas
- B. parathyroid
- C. adrenal medulla
- D. ovary
Correct Answer: D
Rationale: The correct answer is D: ovary. The anterior pituitary gland secretes follicle-stimulating hormone (FSH) and luteinizing hormone (LH) that regulate the function of the ovaries. FSH stimulates the growth of ovarian follicles, while LH triggers ovulation and stimulates the production of progesterone and estrogen. The pancreas (A) is mainly controlled by insulin and glucagon from the pancreas itself. The parathyroid gland (B) is regulated by parathyroid hormone (PTH) secreted by the parathyroid glands. The adrenal medulla (C) is controlled by the sympathetic nervous system, not by anterior pituitary hormones.
Which of the following is a symptom of Addison’s disease?
- A. Hypertension
- B. Weight gain
- C. Hyperpigmentation
- D. Tachycardia
Correct Answer: C
Rationale: The correct answer is C: Hyperpigmentation. Addison's disease is a condition characterized by adrenal insufficiency, leading to decreased production of cortisol and aldosterone. Hyperpigmentation is a common symptom due to elevated levels of ACTH stimulating melanin production. Other choices are incorrect because Addison's disease typically presents with hypotension, weight loss, and bradycardia, rather than hypertension, weight gain, or tachycardia.
Which is NOT an action of CCK?
- A. gallbladder contraction
- B. increased gastric motility and emptying
- C. glucagon secretion
- D. secretion of pancreatic juice
Correct Answer: B
Rationale: The correct answer is B: increased gastric motility and emptying. CCK, or cholecystokinin, is a hormone released by the small intestine in response to the presence of fats. Its main actions include stimulating gallbladder contraction (A) to release bile for fat digestion, triggering the secretion of pancreatic juice (D) containing digestive enzymes, and inhibiting gastric motility and emptying. Therefore, increased gastric motility and emptying (choice B) is NOT an action of CCK. This is because CCK acts to slow down gastric emptying to allow for effective digestion of fats in the small intestine. Choices A, C, and D are all correct actions of CCK based on its role in the digestive process.
Where Are Islets of Langerhans Found?
- A. Anterior pituitary
- B. Cortex
- C. Spleen
- D. Endocrine pancreas
Correct Answer: D
Rationale: The Islets of Langerhans are clusters of cells in the pancreas that regulate blood sugar levels. Choice D, Endocrine pancreas, is correct because the Islets of Langerhans are specifically located in the pancreas. Choices A, B, and C are incorrect because the Islets of Langerhans are not found in the anterior pituitary, cortex, or spleen. The pancreas is the primary organ associated with blood sugar regulation, making it the correct location for the Islets of Langerhans.