The chemical signaling system that relies on blood transport uses

Correct Answer: C

Rationale: Endocrine signaling uses blood vessels to transport hormones (e.g., cortisol) to targets, enabling systemic effects. Neurons signal electrically/chemically, not via blood transport distinct system. Ducts are exocrine (e.g., sweat glands), not endocrine. Membranes facilitate receptor binding, not transport. Blood vessels' role distinguishes endocrine reach, critical for widespread regulation, unlike neural, exocrine, or cellular mechanisms.

Correct Answer: B

Rationale: Hypothalamus produces ADH (water) and oxytocin (labor), stored/released by posterior pituitary neurohypophyseal pair. Aldosterone is adrenal, not hypothalamic. Prolactin is anterior pituitary, not posterior. Cortisol is adrenal cortex, unrelated. ADH-oxytocin duo distinguishes posterior pituitary function, key to hypothalamic delivery, unlike adrenal or anterior hormones.

Correct Answer: C

Rationale: GH overproduction in adults causes acromegaly bone thickening (e.g., hands, face) post-epiphyseal closure. Dwarfism is childhood GH lack. Gigantism is pre-closure excess height surge. Myxedema is hypothyroidism, unrelated. Acromegaly's adult-specific bone changes distinguish it, key to GH excess timing, unlike childhood or thyroid conditions.

Correct Answer: D

Rationale: PTH (parathyroid) raises blood calcium by bone resorption, opposing calcitonin's lowering via deposition antagonistic pair. Thyroxine (thyroid) boosts metabolism, not calcium directly. GH (pituitary) grows bones, not regulating calcium. Insulin (pancreas) lowers glucose, unrelated. PTH's calcium-raising role distinguishes it, key to homeostasis, unlike metabolic, growth, or glucose hormones.

Correct Answer: A

Rationale: ANH (atria) opposes aldosterone by promoting natriuresis, lowering blood volume/pressure antagonistic to aldosterone's sodium retention. ADH (pituitary) retains water, synergistic at times. Cortisol (adrenal) is glucocorticoid, minimal overlap. Glucagon (pancreas) raises glucose, unrelated. ANH's natriuretic effect distinguishes it, key to volume counterbalance, unlike water, stress, or glucose hormones.