The ability of a specific tissue or organ to respond to the presence of a hormone is dependent on ________.

Correct Answer: C

Rationale: The correct answer is C because the ability of a tissue or organ to respond to a hormone depends on the presence of specific receptors on the cells of the target tissue. These receptors are like locks that only fit the specific key (hormone). Without the appropriate receptors, the hormone cannot initiate a response. A: The location of the tissue or organ with respect to the circulatory path may affect the speed of hormone delivery but does not determine the tissue's ability to respond. B: The membrane potential of the cells of the target organ relates to cell signaling but does not determine the specificity of hormone response. D: This choice is incorrect because hormones are specific and can only bind to cells with the appropriate receptors, making the statement that all hormones can stimulate any cell type nonsensical.

Correct Answer: C

Rationale: Step 1: Up-regulation refers to the process where cells increase the number of receptors in response to increased hormone levels. Step 2: This allows cells to become more sensitive to the hormone and maintain homeostasis. Step 3: The other choices are incorrect because they do not accurately describe the phenomenon of up-regulation. Step 4: Option A refers to sensitivity reaction in general, not specifically related to hormone receptors. Step 5: Option B does not accurately describe the process of increasing receptor numbers. Step 6: Option D mentions a reaction to a stressor, which is not directly related to the regulation of hormone receptors.

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: C

Rationale: The correct answer is C: positive feedback. Oxytocin release is triggered by the positive feedback mechanism. When oxytocin is released in response to a stimulus, it further stimulates the release of more oxytocin, intensifying the effect. This continuous loop enhances the initial response, leading to a cascade effect. Negative feedback (choice A) works to maintain homeostasis by counteracting the initial stimulus, which is not the case for oxytocin release. Neutral feedback (choice B) does not play a significant role in regulating hormone release. Choice D is incomplete and irrelevant.

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.