A small band of dense, white and fibrous elastic tissue is grouped as

Correct Answer: A

Rationale: A ligament is a small, dense, white, fibrous band of elastic tissue connecting bones to stabilize joints, like the anterior cruciate ligament in the knee. Its collagen-rich structure provides strength and slight elasticity. A muscle junction (e.g., neuromuscular) involves nerve-muscle interaction, not fibrous tissue. Muscle filaments are actin/myosin within muscle cells, not bands. Muscle cartilage isn't a term cartilage is avascular, unlike fibrous tissue. Ligaments' role in joint support and their fibrous, elastic nature match the description perfectly, making them the correct choice, as they're distinct from muscle components or junctions in both structure and function.

Correct Answer: B

Rationale: Fast-twitch fibers fatigue quickly, relying on anaerobic glycolysis for rapid, powerful contractions, like sprinting, depleting ATP and accumulating lactic acid fast. Slow-twitch fibers, rich in mitochondria and myoglobin, use aerobic respiration for endurance, fatiguing slower, as in marathons. Equal fatigue ignores their metabolic differences. Non-fatiguing fibers don't exist both tire, but at different rates. Fast-twitch's high-energy, low-endurance profile contrasts slow-twitch's sustained capacity, distinguishing their roles in activity duration and fatigue onset.

Correct Answer: D

Rationale: Trapezius adducts the scapula, pulling it toward the spine, and extends the head backward when both sides contract. Buccinator compresses cheeks. Serratus anterior protracts scapula, not adducts. Sternocleidomastoid turns the head. Trapezius' dual role in scapular and neck movement sets it apart, key for posture and head positioning.

Correct Answer: D

Rationale: Iliopsoas flexes the thigh, lifting it toward the torso, as in stepping. Gluteus maximus extends it, straightening the hip, as in standing. Abduction-adduction involves lateral shifts, not their hip-centric actions. Flexion-extension captures their opposing roles, distinct from side movements, essential for thigh positioning.

Correct Answer: A

Rationale: Myasthenia gravis, an autoimmune condition, weakens muscles by antibodies destroying acetylcholine receptors, impairing nerve-muscle signals, causing fatigue. Amyotrophic lateral sclerosis (ALS, Lou Gehrig's) is neurodegenerative, not autoimmune. Fibromyalgia is pain-focused, not receptor-based. Myasthenia's receptor-specific weakness sets it apart, treatable with immunosuppressants, distinct from nerve or pain conditions.