Most endocrine secretions are controlled by _____.

Correct Answer: B

Rationale: Step 1: Negative feedback is the primary mechanism in endocrine system regulation to maintain homeostasis. Step 2: When hormone levels reach a certain set point, negative feedback signals the gland to stop producing that hormone. Step 3: This ensures that hormone levels remain within a specific range. Step 4: Positive feedback would lead to further hormone secretion, disrupting homeostasis. Step 5: Neural feedback is not a common mechanism for regulating endocrine secretions.

Correct Answer: B

Rationale: The correct answer is B because parathyroid hormone (PTH) actually increases blood calcium levels. PTH achieves this by releasing calcium from bone (A), promoting reabsorption of calcium in the kidneys (C), and activating Vitamin D for increased calcium absorption in the intestines (D). By decreasing blood calcium levels, it would go against the primary function of PTH. This choice is incorrect as PTH is known for its role in increasing blood calcium levels through the mentioned mechanisms.

Correct Answer: C

Rationale: Rationale: C is correct because insulin does not stimulate the breakdown of glycogen. Insulin promotes the storage of glucose as glycogen, not its breakdown. A, B, and D are incorrect because insulin does stimulate cellular absorption of glucose, usage of glucose for energy, and lowers blood glucose levels, respectively. Insulin's main role is to facilitate the uptake and storage of glucose, not its breakdown.

Correct Answer: A

Rationale: The correct answer is A: Diarrhoea. Hypothyroidism is associated with decreased metabolic function, leading to symptoms such as lethargy, anorexia, and weight gain. Diarrhoea is not typically a symptom of hypothyroidism; instead, it can be seen in conditions like hyperthyroidism where there is an excess of thyroid hormone. In hypothyroidism, the digestive processes slow down, which can lead to constipation rather than diarrhoea. Therefore, the effects of hypothyroidism do not include diarrhoea.

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.