This is an example of stretch reflex stimulated by passive muscle movement

Correct Answer: A

Rationale: A stretch reflex occurs when a muscle is passively stretched, triggering a rapid contraction to resist the stretch, mediated by muscle spindles and a monosynaptic reflex arc. The classic example is the knee-jerk response, where tapping the patellar tendon stretches the quadriceps, causing an immediate kick. This reflex tests spinal nerve function and is widely recognized in clinical settings. A tendon reflex, while related to tension, typically involves Golgi tendon organs inhibiting contraction, not initiating it. A flexor reflex is a polysynaptic withdrawal response to pain, not passive stretch. An ipsilateral reflex occurs on the same side but isn't specific to stretch. The knee-jerk response perfectly exemplifies a stretch reflex due to its simplicity and direct muscle activation, making it the best fit, as it's a foundational concept in neurophysiology for assessing reflex integrity.

Correct Answer: B

Rationale: Post-exercise deep breathing repays oxygen debt the oxygen deficit incurred when demand exceeds supply during intense activity. This restores oxygen to myoglobin, oxidizes lactic acid back to pyruvate, and regenerates ATP via aerobic respiration. Fatigue is a symptom, not the cause of breathing. Lactic acid accumulation contributes to debt but isn't the full reason oxygen replenishes broader systems. Combining them excludes fatigue's role, missing the debt's primacy. Oxygen debt drives this response, addressing metabolic recovery, distinct from fatigue's effect or lactic acid's partial role, key to post-exercise homeostasis.

Correct Answer: B

Rationale: The frontalis, on the forehead, wrinkles the brow and raises eyebrows, creating horizontal lines, as in surprise. Buccinator compresses cheeks, aiding chewing. Orbicularis oculi closes eyes, wrinkling skin around them, not the brow. Zygomaticus lifts mouth corners for smiling. Frontalis' forehead action distinguishes it, key for facial expression above the eyes.

Correct Answer: C

Rationale: Pectoralis major, across the chest, adducts and medially rotates the arm, pulling it toward the midline, as in hugging. Biceps brachii flexes the elbow. Latissimus dorsi adducts from behind, not chest-directed. Triceps brachii extends the elbow. Pectoralis major's anterior pull distinguishes it, key for chest-centric motion, unlike elbow or posterior actions.

Correct Answer: B

Rationale: Hamstrings biceps femoris, semimembranosus, semitendinosus flex the knee and extend the hip, on the posterior thigh. Rectus femoris, an anterior quadriceps, extends the knee. Biceps brachii flexes the elbow, an arm muscle. Semimembranosus and semitendinosus are hamstrings. Rectus femoris' quadriceps role excludes it, distinct from arm or hamstring functions.