Tendons connect bone and

Correct Answer: C

Rationale: Tendons are dense, fibrous tissues linking muscle to bone, transmitting force to enable movement. Made of collagen, they anchor muscles like the quadriceps to bones like the tibia, facilitating actions like kicking. Bone-to-bone connections are ligaments' role, stabilizing joints. Ligaments themselves connect bones, not tendons' function. Cartilage cushions joints but doesn't attach to tendons directly tendons bypass it to reach bone. This muscle-to-bone connection defines tendons' purpose, distinct from ligaments' skeletal linking or cartilage's padding. Their strength and flexibility ensure efficient motion, critical for skeletal muscle function, highlighting their unique role in the musculoskeletal system over other structures misaligned with this mechanical linkage.

Correct Answer: A

Rationale: Within a muscle fiber, the sarcolemma, the cell membrane, extends inward as transverse tubules, known as T-tubules. These structures penetrate deep into the fiber, ensuring rapid transmission of action potentials from the nerve impulse to trigger contraction. This allows synchronized calcium release across the fiber, critical for muscle function. The sarcoplasmic reticulum, while closely associated, is a separate organelle storing calcium, not an extension of the sarcolemma. Myofibrils are the contractile units, composed of actin and myosin, but they don't extend from the membrane. Sarcomeres are segments of myofibrils, defining the contractile zone, not membrane extensions. T-tubules' role in signal conduction distinguishes them, enabling efficient, uniform contraction, unlike the storage, structural, or organizational roles of the others, aligning with their anatomical and physiological purpose in muscle activation.

Correct Answer: D

Rationale: Relaxation requires multiple steps: the nerve impulse stopping halts T-tubule signals, calcium being pumped back into the sarcoplasmic reticulum (SR) removes it from troponin, shifting tropomyosin to block actin sites, and ATP binding myosin detaches it from actin, ending cross-bridges. One alone like impulse cessation won't suffice without calcium removal and detachment. Calcium pumping alone leaves myosin bound if ATP's absent. ATP detachment needs prior steps. All must occur, ensuring contraction ceases fully, distinct from partial processes, restoring the muscle to rest, integral to its cyclic function.

Correct Answer: D

Rationale: The tibialis anterior's name reflects its location anterior (front) of the tibia in the lower leg. Muscle names often denote position, here indicating its role in dorsiflexing the foot from the shin's front. Size (e.g., maximus) or shape (e.g., deltoid) apply elsewhere, not here. Fiber direction (e.g., oblique) isn't the focus location is. This positional naming distinguishes it, aligning with anatomical convention for identifying muscle placement and function.

Correct Answer: A

Rationale: The diaphragm, a dome-shaped muscle below the lungs, contracts to flatten, expanding the thoracic cavity for inspiration breathing's primary driver. External intercostals assist, lifting ribs, but diaphragm's action is dominant. Internal intercostals aid expiration, secondary to inspiration. Rectus abdominis flexes the trunk, not breathing. Diaphragm's central role in volume change sets it apart, essential for respiratory rhythm.