Which feature is shared by cardiac muscle cells and skeletal muscle cells?

Correct Answer: A

Rationale: Both cardiac and skeletal muscle cells display striations banded patterns from sarcomere alignment unlike smooth muscle. Intercalated discs, branching, and involuntary control are cardiac-specific, aiding heart synchronization and automaticity. Striations reflect shared contractile machinery, distinguishing them from non-striated smooth muscle, key to their histological and functional similarity.

Correct Answer: B

Rationale: These muscles triceps brachii (three origins, arm), biceps femoris (two origins, thigh), quadriceps femoris (four origins, thigh) are named by origin count ('tri-,' 'bi-,' 'quad-') and location ('brachii' for arm, 'femoris' for femur). Size, shape, fibre direction, or insertions aren't specified. This origin-location convention aids anatomical identification, distinguishing them from size- or shape-based names, reflecting muscle attachment points critical for function.

Correct Answer: B

Rationale: ATP hydrolysis to ADP and phosphate energizes myosin cross-bridges, enabling them to pull actin, driving contraction. Myosin doesn't shorten, calcium binds troponin (not tropomyosin), and calcium returns to the sarcoplasmic reticulum post-contraction. This energy step distinguishes contraction's power source, essential for filament sliding, contrasting with regulatory or recovery phases.

Correct Answer: A

Rationale: Biceps femoris, a hamstring, acts on the femur and tibia, not the humerus (upper arm). Quadriceps extend the tibia, gluteals move the femur, and biceps brachii flex the radius. This mismatch distinguishes humerus-biceps femoris as non-functional, key to anatomical pairing accuracy.