BIOS251 Anatomy & Physiology I - Exam 3 Questions and Answers and
Explanations | Latest Chamberlain
1. What is the functional unit of a skeletal muscle fiber?
A. Myofibril
B. Sarcomere
C. Sarcoplasmic reticulum
D. T-tubule
Answer: B
Explanation: The sarcomere is the basic functional unit of a myofibril, extending from one
Z disc to the next.
2. Which protein covers the myosin-binding sites on actin in a relaxed muscle?
A. Troponin
B. Tropomyosin
C. Titin
D. Myosin
Answer: B
Explanation: Tropomyosin is a regulatory protein that blocks the active sites on actin to
prevent contraction when the muscle is at rest.
,3. Which ion is primarily responsible for triggering muscle contraction when
released from the sarcoplasmic reticulum?
A. Sodium
B. Potassium
C. Magnesium
D. Calcium
Answer: D
Explanation: Calcium ions bind to troponin, causing a conformational change that moves
tropomyosin away from the binding sites.
4. The neurotransmitter released at the neuromuscular junction is:
A. Dopamine
B. Norepinephrine
C. Serotonin
D. Acetylcholine
Answer: D
Explanation: Acetylcholine (ACh) is the specific neurotransmitter used by motor neurons
to stimulate skeletal muscle fibers.
5. What is the role of ATP in the sliding filament theory?
A. It binds to troponin
B. It powers the power stroke and detaches the myosin head
, C. It opens sodium channels
D. It forms the Z-line
Answer: B
Explanation: ATP hydrolysis provides energy for the power stroke, and a new ATP
molecule must bind to the myosin head to release it from actin.
6. Which type of muscle contraction occurs when the muscle develops tension
but does not shorten?
A. Isotonic
B. Isometric
C. Eccentric
D. Concentric
Answer: B
Explanation: Isometric contractions involve tension generation without a change in
muscle length or joint movement.
7. Which muscle fiber type is highly resistant to fatigue and has many
mitochondria?
A. Fast glycolytic fibers
B. Fast oxidative-glycolytic fibers
C. Slow oxidative fibers
D. Type IIb fibers
Explanations | Latest Chamberlain
1. What is the functional unit of a skeletal muscle fiber?
A. Myofibril
B. Sarcomere
C. Sarcoplasmic reticulum
D. T-tubule
Answer: B
Explanation: The sarcomere is the basic functional unit of a myofibril, extending from one
Z disc to the next.
2. Which protein covers the myosin-binding sites on actin in a relaxed muscle?
A. Troponin
B. Tropomyosin
C. Titin
D. Myosin
Answer: B
Explanation: Tropomyosin is a regulatory protein that blocks the active sites on actin to
prevent contraction when the muscle is at rest.
,3. Which ion is primarily responsible for triggering muscle contraction when
released from the sarcoplasmic reticulum?
A. Sodium
B. Potassium
C. Magnesium
D. Calcium
Answer: D
Explanation: Calcium ions bind to troponin, causing a conformational change that moves
tropomyosin away from the binding sites.
4. The neurotransmitter released at the neuromuscular junction is:
A. Dopamine
B. Norepinephrine
C. Serotonin
D. Acetylcholine
Answer: D
Explanation: Acetylcholine (ACh) is the specific neurotransmitter used by motor neurons
to stimulate skeletal muscle fibers.
5. What is the role of ATP in the sliding filament theory?
A. It binds to troponin
B. It powers the power stroke and detaches the myosin head
, C. It opens sodium channels
D. It forms the Z-line
Answer: B
Explanation: ATP hydrolysis provides energy for the power stroke, and a new ATP
molecule must bind to the myosin head to release it from actin.
6. Which type of muscle contraction occurs when the muscle develops tension
but does not shorten?
A. Isotonic
B. Isometric
C. Eccentric
D. Concentric
Answer: B
Explanation: Isometric contractions involve tension generation without a change in
muscle length or joint movement.
7. Which muscle fiber type is highly resistant to fatigue and has many
mitochondria?
A. Fast glycolytic fibers
B. Fast oxidative-glycolytic fibers
C. Slow oxidative fibers
D. Type IIb fibers
