Which of the following is the property in which a hormone CANNOT exhibit its full effect without another hormone?

Correct Answer: D

Rationale: The correct answer is D: permissiveness. Permissiveness is when one hormone enables another hormone to fully exert its effects. The rationale is as follows: 1. Permissiveness allows a hormone to work effectively only when another hormone is present to "permit" its action. 2. Assertiveness (A) and antagonism (B) do not involve the requirement of another hormone for full effect. 3. Synergism (C) involves two hormones working together for a greater effect, but they can still exert some effect individually. In summary, permissiveness is the only option where a hormone cannot exhibit its full effect without the presence of another hormone.

Correct Answer: C

Rationale: The correct answer is C because the release of hormones by the parathyroid glands is actually controlled by the levels of calcium in the blood, not by the pituitary gland. A: True - Parathyroid glands are four small yellowish brown ovoid glands. B: True - They lie in relation to the posterior border of thyroid lobes. D: True - The hormone produced by the parathyroid glands, parathyroid hormone (PTH), controls blood calcium levels by stimulating the release of calcium from bones and increasing the absorption of calcium from the intestines.

Correct Answer: d

Rationale: Rationale for Correct Answer (D): 1. Ca2+ ions do not directly break down ATP into ADP + inorganic phosphate at the sarcomere. 2. This breakdown occurs through the enzymatic action of myosin ATPase. 3. Ca2+ ions primarily bind to troponin to initiate muscle contraction by moving tropomyosin. 4. Ca2+ ions help expose active sites on actin, facilitating cross-bridge formation. Summary of Incorrect Choices: A. Correct - Ca2+ binds to troponin to move tropomyosin, not to uncover it. B. Correct - Ca2+ aids in exposing active sites on actin, not troponin. C. Correct - Ca2+ is stored in the sarcoplasmic reticulum, but it is released into the cytoplasm to trigger muscle contraction, not stored in the terminal cisternae.

Correct Answer: A

Rationale: Step-by-step rationale for choice A being correct: 1. ADH and oxytocin are peptide hormones. 2. They are synthesized in the hypothalamus. 3. They are transported and stored in the neurohypophysis. 4. Upon stimulation, they are released from the neurohypophysis. 5. Therefore, both ADH and oxytocin are indeed secreted by the neurohypophysis. Summary of why other choices are incorrect: B: ADH and oxytocin are not mineralocorticoids; they regulate water balance and uterine contractions, respectively. C: Islets of Langerhans secrete insulin and glucagon, not ADH or oxytocin. D: ADH promotes water reabsorption in the kidneys, opposite to excreting Na+ and water.

Correct Answer: D

Rationale: Rationale: 1. Insulin, cortisol, thyroxine, and oxytocin are all hormones produced by various glands in the body. 2. Insulin is produced by the pancreas, cortisol by the adrenal glands, thyroxine by the thyroid gland, and oxytocin by the hypothalamus and released by the pituitary gland. 3. Each of these hormones plays a different role in the body, such as regulating blood glucose levels, metabolism, stress response, and reproductive functions. 4. Therefore, the correct answer is D: they are all hormones. Summary: A: Incorrect. Hypothalamic-releasing hormones are specific hormones that stimulate the release of other hormones from the pituitary gland. B: Incorrect. Adenohypophysis secretes different hormones, not these specific ones. C: Incorrect. Insulin, for example, decreases blood glucose levels, while cortisol increases blood glucose levels.