NASM Applied Sciences & Nutrition 3 — Questions and Answers
Question 1: Which structure is the functional unit of the muscle responsible for contraction?
- Sarcomere (Correct answer)
- Sarcolemma
- Endomysium
- Fascicle
Correct answer: Sarcomere
The sarcomere is the smallest contractile unit of skeletal muscle, defined by the area between two Z-lines.
Question 2: During the sliding filament theory, which protein filament physically pulls the actin toward the center of the sarcomere?
- Troponin
- Tropomyosin
- Myosin (Correct answer)
- Titin
Correct answer: Myosin
Myosin cross-bridges attach to actin and pull it inward, shortening the sarcomere.
Question 3: Which type of muscle fiber is best suited for prolonged, low-intensity aerobic endurance activity?
- Type IIx fibers
- Type IIa fibers
- Type I (slow-twitch) fibers (Correct answer)
- Cardiac fibers
Correct answer: Type I (slow-twitch) fibers
Type I slow-twitch fibers are fatigue-resistant and rely on aerobic metabolism, ideal for endurance.
Question 4: What neurotransmitter is released at the neuromuscular junction to initiate muscle contraction?
- Dopamine
- Acetylcholine (Correct answer)
- Serotonin
- Norepinephrine
Correct answer: Acetylcholine
Acetylcholine is released at the motor end plate to trigger an action potential in the muscle fiber.
Question 5: A motor unit consists of which two components?
- A tendon and its attached bone
- A motor neuron and all the muscle fibers it innervates (Correct answer)
- Two adjacent sarcomeres
- An artery and the muscle it supplies
Correct answer: A motor neuron and all the muscle fibers it innervates
A motor unit is a single motor neuron together with all of the muscle fibers it innervates.
Question 6: Which mineral is essential for muscle contraction by binding to troponin to expose actin binding sites?
- Calcium (Correct answer)
- Iron
- Potassium
- Zinc
Correct answer: Calcium
Calcium binds troponin, shifting tropomyosin to expose actin's binding sites for cross-bridge formation.
Question 7: What is the term for a muscle action in which the muscle lengthens under tension, such as lowering a dumbbell during a biceps curl?
- Concentric action
- Isometric action
- Eccentric action (Correct answer)
- Isokinetic action
Correct answer: Eccentric action
An eccentric action occurs when the muscle produces force while lengthening, controlling the load.
NASM Applied Sciences & Nutrition 3
Which structure is the functional unit of the muscle responsible for contraction?