1. Which muscle is primarily responsible for the abduction of the shoulder? A) Deltoid B) Pectoralis Major C) Latissimus Dorsi D) Trapezius Answer: A) Deltoid Rationale: The deltoid muscle, due to its location and fiber direction, is the primary muscle responsible for shoulder abduction. 2. During a muscle contraction, what happens to the A-band within the sarcomere? A) It shortens. B) It lengthens. C) It remains unchanged. D) It disappears. Answer: C) It remains unchanged. Rationale: The A-band contains the length of the myosin filaments and remains constant during muscle contraction. 3. What is the role of calcium ions (Ca2+) in muscle contractions? A) They bind to myosin, allowing actin filaments to slide. B) They bind to troponin, causing a conformational change in tropomyosin. C) They activate ATPase, which provides energy for muscle contraction. D) They decrease the affinity of actin for myosin, inhibiting contraction. Answer: B) They bind to troponin, causing a conformational change in tropomyosin. Rationale: Calcium ions bind to troponin, which causes tropomyosin to move away from the binding sites on actin filaments, allowing for muscle contraction. 4. Which of the following muscles is involved in the flexion of the elbow? A) Biceps Brachii B) Triceps Brachii C) Brachialis D) Anconeus Answer: A) Biceps Brachii