🩺 NEET🧬 Biology

Chemical Coordination and Integration

3 solved NEET Biology previous year questions on Chemical Coordination and Integration, each with the correct answer and a full explanation.

Fight-or-flight reactions cause activation of;

athe parathyroid glands, leading to increased metabolic rate.

bthe kidney, leading to suppression of reninangiotensin-aldosterone pathway.

cthe adrenal medulla, leading to increased secretion of epinephrine and norepinephrine.

dthe pancreas leading to a reduction in the blood sugar levels.

✓ Correct answer: c) the adrenal medulla, leading to increased secretion of epinephrine and norepinephrine.

ExplanationThe "fight-or-flight" response is an acute stress reaction triggered by the sympathetic nervous system in response to perceived danger or emergency.Activation of Adrenal Medulla (C): When the brain (specifically the hypothalamus) perceives a threat, it sends nerve impulses to the adrenal medulla (the inner part of the adrenal glands).This triggers the rapid release of catecholamines—epinephrine (adrenaline) and norepinephrine (noradrenaline)—into the bloodstream.These "emergency hormones" prepare the body for immediate action by increasing heart rate, blood pressure, and breathing rate, and by mobilising energy sources like glucose.A. Parathyroid glands: These glands regulate calcium and phosphate levels in the blood; they are not directly involved in the rapid fight- or-flight metabolic surge.B. Kidney (Renin-angiotensin-aldosterone): While stress can eventually impact kidney function, the fight-or-flight response typically leads to the activation (or "triggering") of the renin-angiotensin-aldosterone system (RAAS) to maintain blood pressure, not its suppression.D. Pancreas: During fight-or-flight, the body needs more sugar for energy.Activation actually leads to an increase in blood sugar levels (via the breakdown of glycogen in the liver), not a reduction.

The amino acid tryptophan is the precursor for the synthesis of

aThyroxine and tri-iodothyronine

bEstrogen and progesterone

cCortisol and cortisone

dMelatonin and Serotonin

✓ Correct answer: d) Melatonin and Serotonin

ExplanationTryptophan is the precursor for the synthesis of Serotonin (a neurotransmitter) and Melatonin (a hormone secreted by the pineal gland). [New NCERT Class 11 Page No. 338]

Select the correct statement [NEET 2020]

aGlucagon is associated with hypoglycemia.

bInsulin acts on pancreatic cells and adipocytes.

cInsulin is associated with hyperglycemia.

dGlucocorticoids stimulate gluconeogenesis.

✓ Correct answer: d) Glucocorticoids stimulate gluconeogenesis.

Explanation(D) Glucocorticoids (like cortisol) are steroid hormones produced by the adrenal cortex that promote gluconeogenesis, the process of generating glucose from non-carbohydrate sources, primarily in the liver.This increases blood glucose levels during stress or fasting.

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