By what name is the plasma membrane of a muscle cell known?

Correct Answer: D

Rationale: In muscle cells, specialized terminology distinguishes structures. The plasma membrane, enveloping the cell, is the sarcolemma sarco meaning flesh, lemma a sheath serving as the boundary for nerve signal transmission and ion exchange. Sarcoplasm is the cytoplasm, sarcomeres are contractile units within myofibrils, and the sarcoplasmic reticulum stores calcium. The sarcolemma's role in action potential propagation, via T-tubules, initiates contraction, setting it apart from internal components. This unique naming reflects muscle cells' adaptation for rapid, coordinated responses, essential in physiology for understanding excitation-contraction coupling.

Correct Answer: A

Rationale: The deltoid, in the upper arm's shoulder region, is a standard intramuscular injection site due to its accessible, thick muscle mass, minimizing nerve damage risk. Gluteus maximus is avoided to protect the sciatic nerve (gluteus medius is preferred), vastus medialis isn't typical, and latissimus dorsi, on the back, lacks suitable mass and access. Deltoid's prominence and safety distinguish it in clinical practice, key for effective drug delivery.

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: D

Rationale: Skeletal muscle is striated (sarcomere-banded), voluntary (somatic control), and multinucleate (syncytial), unlike smooth (unstriated, involuntary, uninucleate) or cardiac (striated, involuntary, uninucleate) muscle. This trio defines its role in conscious movement, distinguishing it in structure and function, key to its physiological classification.

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.