Part of the effect of growth hormone is influenced by a group of protein chemical signals called:

Correct Answer: A

Rationale: Somatomedin-C (IGF-1), a liver-derived protein induced by growth hormone (GH), mediates GH's anabolic effects, promoting bone and muscle growth. Gonadotropins (FSH, LH) target gonads, not GH pathways. Prostaglandins regulate inflammation and smooth muscle, not growth. Prolactin drives lactation, not GH effects. Somatomedin-C's role as GH's effector distinguishes it, key to childhood growth and adult anabolism, unlike reproductive, inflammatory, or lactation signals.

Correct Answer: C

Rationale: Rapid-acting effects typify neural responses (e.g., milliseconds), not endocrine, where hormones travel via blood (e.g., insulin), causing slow, cyclic changes (e.g., menstrual cycle) via chemical signals. Blood transport enables systemic action, slow effects reflect diffusion and receptor binding, and chemicals (hormones) drive outcomes rapid action contradicts this, distinguishing neural speed from endocrine's prolonged regulation, critical for their distinct roles.

Correct Answer: A

Rationale: Epinephrine and norepinephrine, from the adrenal medulla, drive fight-or-flight, raising heart rate, glucose, and alertness via sympathetic activation. Insulin/glucagon regulate glucose, not acute stress. Estrogen/progesterone manage reproduction, not emergency responses. Thyroxin (metabolism) and melatonin (sleep) lack rapid stress roles. Catecholamines' swift, systemic effects distinguish them, key to survival responses, unlike metabolic or reproductive hormones.

Correct Answer: C

Rationale: Gonadal glands (testes, ovaries) differ testes secrete testosterone, ovaries estrogen/progesterone, shaping sex-specific traits. Adrenal (cortisol, aldosterone), parathyroid (PTH), and pancreas (insulin) secretions are sex-agnostic, serving universal functions (stress, calcium, glucose). Gonadal hormone divergence distinguishes them, critical for reproductive dimorphism, unlike consistent outputs.

Correct Answer: A

Rationale: Hormonal stimuli, like TSH stimulating thyroid hormone release, drive most endocrine activity. Humoral stimuli (e.g., blood calcium for PTH) and neural stimuli (e.g., adrenal medulla) exist, but hormonal is predominant. 'Receptor-mediated' isn't a stimulus type. This prevalence distinguishes endocrine regulation, key to hormonal cascades, contrasting with chemical or nerve triggers.