Why do we breathe deeply following strenuous exercise, even while resting?

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: 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.

Correct Answer: B

Rationale: The joint connecting the neck to the head, specifically the atlas (C1) and skull's occipital condyles, allows rotational and nodding movements. This atlanto-occipital joint permits flexion, extension, and slight lateral tilting, while the atlas-axis (C1-C2) adds pivoting, as in turning the head side to side. This fits the pivotal joint category, where a bone rotates within a ring-like structure, exemplified by the atlas pivoting around the axis' dens. Ball-and-socket joints, like the shoulder, offer multi-axial rotation and swinging, exceeding neck motion. Hinge joints, such as the elbow, limit movement to one plane, unlike the neck's range. Fixed joints, like skull sutures, allow no motion. The pivotal joint's rotational capacity matches the neck-head junction's function, distinguishing it in skeletal articulation classifications.

Correct Answer: D

Rationale: Superficial back muscles, like trapezius (shoulder elevation), latissimus dorsi (arm adduction), and rhomboid major/minor (scapula retraction), lie under skin, moving the shoulder girdle. Vastus lateralis, a quadriceps component, is on the anterior thigh, extending the knee, not the back. Rhomboid minor, replaced here, is superficial with major, but vastus lateralis' thigh location excludes it. Its leg-focused action contrasts with back muscles' upper body roles, distinguishing it in musculoskeletal grouping.