The chemicals of the endocrine system affect their target cells by binding to

Correct Answer: A

Rationale: Hormones bind receptors (e.g., insulin to tyrosine kinase) on target cells, triggering responses like glucose uptake specificity defines action. Blood cells transport, not bind hormones as targets. Neurotransmitters signal neurons, not endocrine targets separate system. Enzymes process, not receive hormones. Receptor binding distinguishes endocrine signaling, critical for cellular response, unlike transport, neural, or catalytic roles.

Correct Answer: C

Rationale: Oxytocin stimulates uterine contractions (labor) and milk ejection (nursing) via myoepithelial cells dual reproductive role. ADH manages water, not reproduction. Glucagon raises glucose, unrelated. Prolactin drives milk production, not release. Oxytocin's contractile action distinguishes it, key to birth and lactation, unlike water, glucose, or synthesis hormones.

Correct Answer: C

Rationale: GH underproduction in childhood causes pituitary dwarfism short stature from poor bone growth pre-closure. Myxedema is adult hypothyroidism low metabolism. Gigantism is GH excess tallness. Acromegaly is adult excess thickening. Dwarfism's growth deficit distinguishes it, key to GH's developmental role, unlike thyroid or excess conditions.

Correct Answer: D

Rationale: Adrenal glands secrete cortisol (cortex, stress) and aldosterone (cortex, sodium) dual zones (fasciculata, glomerulosa). Thyroid produces T3/T4, calcitonin metabolism/calcium. Parathyroid releases PTH calcium only. Pancreas makes insulin/glucagon glucose. Adrenal's steroid output distinguishes it, key to stress and electrolyte balance, unlike metabolic or calcium glands.

Correct Answer: B

Rationale: ANH, from right atrial cells, responds to stretch (high volume), lowering pressure via natriuresis cardiac origin. Kidney tubules respond, not produce. Adrenal cortex makes aldosterone, opposing ANH. Pancreas focuses on glucose. Atrial production distinguishes ANH, key to heart-volume regulation, unlike renal, adrenal, or metabolic sources.