The flexor carpi ulnaris will

Correct Answer: B

Rationale: The flexor carpi ulnaris flexes the wrist on the ulnar (medial) side, bending it toward the forearm's little-finger edge. 'Flexor' indicates bending, 'carpi' targets the wrist, and 'ulnaris' specifies the ulna's side. Flexing or extending the ulna itself misinterprets bones don't flex, joints do. Extending the wrist contradicts 'flexor.' Its action aligns with wrist movement, distinct from bone or opposite motions, key for hand positioning.

Correct Answer: C

Rationale: Quadriceps extend the knee, straightening the leg, while hamstrings flex it, bending it, acting as antagonists at the knee joint. Abduction-adduction involves lateral-medial thigh motion, not their primary knee focus. Extension-flexion defines their opposing actions, distinct from side movements, crucial for leg dynamics.

Correct Answer: B

Rationale: Sarcomere shortening, the basis of muscle contraction, occurs via the sliding filament mechanism. Myosin heads, protruding from thick filaments, bind to actin on thin filaments, forming cross-bridges. Using ATP-derived energy, these heads execute a power stroke, pulling actin toward the sarcomere's center specifically the A band's midpoint reducing the distance between Z lines and shortening the sarcomere. Acetylcholine initiates this by triggering an action potential, but it's not the direct shortening mechanism. Calcium release from the sarcoplasmic reticulum enables myosin-actin binding by shifting tropomyosin, a crucial step but not the act of shortening. ATP breakdown powers the process, yet the sarcoplasmic reticulum stores calcium, not hydrolyzes ATP for shortening. The myosin-actin interaction is the mechanical driver, making it the precise answer, central to muscle movement and the sliding filament theory.

Correct Answer: C

Rationale: The external occipital protuberance, a midline bump on the occipital bone, is termed the inion, a landmark for neck muscle attachment (e.g., trapezius). The nasion is the forehead-nose junction, a facial point. The acromion, on the scapula, is a shoulder feature, not cranial. The mental protuberance is the chin's prominence on the mandible. Inion's specific occipital location and role in muscle anchorage distinguish it, aligning with skull anatomy, unlike facial, shoulder, or mandibular misnomers.

Correct Answer: D

Rationale: Elite athletes in prolonged high-intensity exercise (>2.5 hours), like marathons, should consume 90 g of glucose plus fructose per hour. This mix leverages multiple transporters (SGLT1 for glucose, GLUT5 for fructose), maximizing absorption beyond glucose's 60 g/h limit, delivering ~1.5 g/min of energy. Solo 60 g glucose caps at 1 g/min, insufficient for sustained high intensity. Adding fructose to 60 g boosts uptake slightly, but 90 g optimizes fuel, reducing fatigue. Excess glucose alone (90 g) overloads SGLT1, risking GI distress. The dual-carb approach distinguishes it, critical for elite endurance performance.