Steroid hormones function by binding to receptor proteins within the ________. Once the hormone binds to a receptor, it activates ______.

Correct Answer: B

Rationale: The correct answer is B because steroid hormones bind to receptor proteins in the nucleus, forming a hormone-receptor complex that directly influences the expression of specific genes. This process leads to the activation or repression of particular genes, resulting in changes in cellular functions. Choices A and C are incorrect because steroid hormones do not bind to receptors in the plasma membrane or use second messengers for signal transduction. Choice D is incorrect as steroid hormones do not directly regulate genes at the plasma membrane level.

Correct Answer: A

Rationale: Rationale: 1. Hashimoto's disease is characterized by the immune system attacking the thyroid gland, leading to hypothyroidism. 2. It is an autoimmune condition where the body produces antibodies that target and destroy thyroid cells. 3. This results in a decrease in thyroid hormone production. 4. Graves disease (choice B) is a form of hyperthyroidism caused by an overactive thyroid gland. 5. Myxedema (choice C) refers to severe hypothyroidism but is not autoimmune. 6. Acromegaly (choice D) is a disorder caused by excess growth hormone production, unrelated to thyroid function.

Correct Answer: B

Rationale: The correct answer is B: right atrium of the heart. Atrial natriuretic hormone (ANH) is produced by specialized cells in the right atrium of the heart called atrial myocytes. When the heart senses an increase in blood volume or pressure, these cells release ANH to help regulate fluid and electrolyte balance by promoting sodium and water excretion by the kidneys. Choices A, C, and D are incorrect because ANH is not produced by the kidney tubules, adrenal cortex, or pancreas. The primary site of ANH production is specifically within the cardiac atria.

Correct Answer: B

Rationale: Correct Answer: B - aldosterone Rationale: 1. Aldosterone is a hormone produced by the adrenal glands that primarily regulates salt and water balance, not fuel metabolism. 2. Insulin helps in lowering blood sugar levels by facilitating glucose uptake by cells. 3. Glucagon stimulates the release of glucose from the liver to raise blood sugar levels. 4. Cortisol plays a role in mobilizing energy stores during stress. Summary: Aldosterone does not directly impact fuel metabolism like insulin, glucagon, and cortisol do. Insulin lowers blood sugar levels, glucagon raises blood sugar levels, and cortisol mobilizes energy stores during stress.

Correct Answer: C

Rationale: The correct answer is C: Myxedema. Insufficient levels of thyroid hormone in adults lead to myxedema due to decreased metabolism and energy production. Goiter (A) is the enlargement of the thyroid gland, not caused by low thyroid hormone levels. Tetany (B) is muscle spasms due to low calcium levels, not related to thyroid hormone deficiency. Cretinism (D) is a condition of severe hypothyroidism in infants, not in adults. Therefore, the correct choice is C as it directly relates to the consequences of low thyroid hormone levels in adults.