NEET 2025 Zoology Question 160 Solution

The adrenal medulla secretes two catecholamines in response to stress or sympathetic stimulation: adrenaline (epinephrine) and noradrenaline (norepinephrine):

• • Commonly called emergency hormones or hormones of Fight or Flight.
• • They elicit coordinated physiological shifts to prepare the organism for intense physical exertion or survival emergencies.

Evaluating sensory and autonomic responses:

• • Pupillary dynamics (Statement A): Catecholamines stimulate $\alpha_1$-adrenergic receptors on the pupillary dilator muscle, causing pupillary dilation (mydriasis) to maximize visual field and light capture. They do NOT cause pupillary constriction (miosis). Hence, Statement A is INCORRECT.
• • Cutaneous dynamics (Statement C): Adrenaline causes contraction of arrector pili muscles attached to hair follicles, causing piloerection (raising of hairs or "goosebumps"). Hence, Statement C is CORRECT.

Evaluating energy mobilization and cardiac performance:

• • Glucose homeostasis (Statement B): Catecholamines stimulate hepatic and muscular glycogenolysis (breakdown of glycogen into glucose) and lipolysis, sharply elevating blood glucose levels. Thus, adrenaline is a potent hyperglycemic hormone. Hence, Statement B is CORRECT.
• • Cardiovascular output (Statement D): By stimulating $\beta_1$-adrenergic receptors on cardiomyocytes, catecholamines exert positive inotropic effects, significantly increasing the strength of heart contraction and cardiac output. Hence, Statement D is CORRECT.

Statements B, C, and D are correct, while Statement A is false. This corresponds to Option (2).