Daily Olympiad: Biology - Human Physiology [20260512]

Challenge yourself with today's NEET practice! This test covers 'Human Physiology' for Biology (NEET - 12). Level: Hard | Duration: 45 mins.

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1. During gas exchange in the human respiratory system, which of the following components carries the highest percentage of carbon dioxide in blood?

Solution
Correct: A
Approximately 70% of CO2 is transported as bicarbonate ions (HCO3⁻) in plasma, formed via CO2 reacting with water in red blood cells. Carbaminohemoglobin carries ~23%, and dissolved CO2 accounts for ~7%. Carbonic acid conversion is part of the bicarbonate pathway but is not the primary form.

2. The hormone responsible for milk ejection in lactating women is primarily secreted by which gland?

Solution
Correct: B
Oxytocin, produced by the hypothalamus and stored in the posterior pituitary, triggers milk ejection via myoepithelial cells in mammary glands. Prolactin from the anterior pituitary stimulates milk production, but ejection is controlled by oxytocin.

3. In the cardiac cycle, which phase is directly associated with the closure of the semilunar valves (aortic and pulmonary valves)?

Solution
Correct: C
Semilunar valves close during ventricular diastole when blood backflow causes a pressure drop below ventricular pressure (dicrotic notch). This prevents retrograde flow into the ventricles during relaxation.

4. Which of the following statements about the nephron loop (Loop of Henle) is incorrect?

Solution
Correct: D
The descending limb of the Loop of Henle is permeable to water, allowing passive reabsorption driven by the medullary gradient. Active transport in the ascending limb creates the medullary concentration gradient essential for urine concentration.

5. In the human endocrine system, which of the following is not a function of adrenaline?

Solution
Correct: D
Adrenaline stimulates glycogenolysis, bronchodilation, and lipolysis. Renin secretion is regulated by the juxtaglomerular apparatus in the kidneys, not directly by adrenaline. Adrenaline is secreted by the adrenal medulla, not cortex.