Elastic bundles of tissue which perform various functions is termed as

Correct Answer: D

Rationale: Muscles are elastic tissue bundles with diverse roles movement, posture, heat production stretching and contracting to function. Skeletal muscles move bones, smooth muscles regulate organs, and cardiac muscles pump blood, showcasing versatility. Tendons, though fibrous, primarily transmit force, not perform varied tasks themselves. Ligaments stabilize joints, limiting motion, not acting broadly. Joints are bone junctions, not tissues. Muscles' elasticity and multifunctional nature contracting for strength, relaxing for flexibility define them, distinguishing their dynamic, active contributions from tendons' and ligaments' supportive, static roles or joints' structural purpose, making them the clear fit for this description.

Correct Answer: C

Rationale: The A band, the dark region of a sarcomere, spans the thick myosin filaments, appearing dark under a microscope due to overlapping actin and myosin in most areas. It remains constant in length during contraction, reflecting myosin's extent. The H-zone, within the A band, is lighter, showing only myosin, narrowing as actin slides in. The Z-line anchors actin, defining sarcomere boundaries, not dark. The I band, light, contains only actin, shortening during contraction. The A band's darkness and myosin content distinguish it, central to sarcomere structure, unlike the lighter, shifting H-zone, structural Z-line, or actin-only I band, key to understanding muscle striation.

Correct Answer: D

Rationale: The latent period in a muscle twitch spans from stimulus to contraction onset, covering action potential travel, T-tubule signaling, and calcium release about 2 milliseconds. Contraction is the active shortening phase, post-latent. Relaxation follows, as muscle returns to rest. Fatigue is a state, not a twitch phase. The latent period's pre-contraction delay is unique, ensuring calcium reaches troponin before movement, distinct from active or recovery phases, critical for timing muscle activation in physiological studies.

Correct Answer: C

Rationale: The depressor anguli oris pulls the mouth's corners down, and depressor labii inferioris lowers the bottom lip, both creating frowning or pouting expressions. Chewing involves masseter and temporalis. Cheek compression is buccinator's role. Smiling uses zygomaticus. These depressors' downward actions contrast with chewing, compression, or upward smiling, key for sad or sulky faces.

Correct Answer: B

Rationale: Spasms are involuntary, sudden muscle contractions, often brief and uncontrolled, like twitches. Cramps are painful, prolonged involuntary contractions, a subset but not the broad term. Strains are muscle overstretching injuries, not contractions. Sprains affect ligaments, not muscles. Spasms' involuntary nature encompasses various unintended movements, distinguishing them from specific pain, injury, or ligament issues, common in muscle dysfunction.