BIOS251 Anatomy & Physiology I - Exam 3 Review Questions and
Answers and Explanations | Latest Chamberlain
1. What is the functional unit of a skeletal muscle fiber?
A. Myofibril
B. Sarcoplasmic reticulum
C. Sarcomere
D. Sarcolemma
Answer: C
Explanation: The sarcomere is the basic functional unit of a skeletal muscle fiber, spanning
from one Z-disc to the next.
2. During muscle contraction, calcium ions bind to which protein to expose the
active sites on actin?
A. Myosin
B. Tropomyosin
C. Troponin
D. Titins
Answer: C
Explanation: Calcium binds to troponin, which then shifts tropomyosin away from the
myosin-binding sites on the actin filament.
,3. Which neurotransmitter is released at the neuromuscular junction to initiate
muscle contraction?
A. Dopamine
B. Acetylcholine
C. Serotonin
D. Norepinephrine
Answer: B
Explanation: Acetylcholine (ACh) is the specific neurotransmitter that crosses the synaptic
cleft at the NMJ to trigger an action potential in the muscle fiber.
4. The state of partial, sustained contraction of a muscle that is necessary for
posture is called:
A. Twitch
B. Muscle tone
C. Tetanus
D. Isotonic contraction
Answer: B
Explanation: Muscle tone (tonus) is the constant tension in a resting muscle that helps
maintain posture and stabilize joints.
,5. Which type of muscle contraction involves a change in muscle length while
the tension remains constant?
A. Isometric contraction
B. Treppe
C. Isotonic contraction
D. Summation
Answer: C
Explanation: In isotonic contractions, the muscle changes length (shortening or
lengthening) while maintaining the same tension.
6. What structure in the muscle fiber stores and releases calcium ions?
A. T-tubule
B. Mitochondria
C. Nucleus
D. Sarcoplasmic reticulum
Answer: D
Explanation: The sarcoplasmic reticulum is a specialized smooth ER that regulates calcium
levels inside the muscle fiber.
7. The ‘All-or-None’ principle applies to:
A. A single muscle fiber
B. The whole muscle organ
, C. The intensity of a stimulus
D. The duration of a contraction
Answer: A
Explanation: The all-or-none principle states that an individual muscle fiber will contract
to its full extent or not at all when stimulated above threshold.
8. Which metabolic pathway provides the quickest source of ATP for a short
burst of activity (e.g., a 100m sprint)?
A. Aerobic respiration
B. Creatine phosphate system
C. Anaerobic glycolysis
D. Beta-oxidation
Answer: B
Explanation: The phosphagen system (creatine phosphate) provides immediate ATP for
activities lasting about 10-15 seconds.
9. The structural classification of a neuron with one axon and many dendrites is:
A. Unipolar
B. Bipolar
C. Anaxonic
D. Multipolar
Answer: D
Answers and Explanations | Latest Chamberlain
1. What is the functional unit of a skeletal muscle fiber?
A. Myofibril
B. Sarcoplasmic reticulum
C. Sarcomere
D. Sarcolemma
Answer: C
Explanation: The sarcomere is the basic functional unit of a skeletal muscle fiber, spanning
from one Z-disc to the next.
2. During muscle contraction, calcium ions bind to which protein to expose the
active sites on actin?
A. Myosin
B. Tropomyosin
C. Troponin
D. Titins
Answer: C
Explanation: Calcium binds to troponin, which then shifts tropomyosin away from the
myosin-binding sites on the actin filament.
,3. Which neurotransmitter is released at the neuromuscular junction to initiate
muscle contraction?
A. Dopamine
B. Acetylcholine
C. Serotonin
D. Norepinephrine
Answer: B
Explanation: Acetylcholine (ACh) is the specific neurotransmitter that crosses the synaptic
cleft at the NMJ to trigger an action potential in the muscle fiber.
4. The state of partial, sustained contraction of a muscle that is necessary for
posture is called:
A. Twitch
B. Muscle tone
C. Tetanus
D. Isotonic contraction
Answer: B
Explanation: Muscle tone (tonus) is the constant tension in a resting muscle that helps
maintain posture and stabilize joints.
,5. Which type of muscle contraction involves a change in muscle length while
the tension remains constant?
A. Isometric contraction
B. Treppe
C. Isotonic contraction
D. Summation
Answer: C
Explanation: In isotonic contractions, the muscle changes length (shortening or
lengthening) while maintaining the same tension.
6. What structure in the muscle fiber stores and releases calcium ions?
A. T-tubule
B. Mitochondria
C. Nucleus
D. Sarcoplasmic reticulum
Answer: D
Explanation: The sarcoplasmic reticulum is a specialized smooth ER that regulates calcium
levels inside the muscle fiber.
7. The ‘All-or-None’ principle applies to:
A. A single muscle fiber
B. The whole muscle organ
, C. The intensity of a stimulus
D. The duration of a contraction
Answer: A
Explanation: The all-or-none principle states that an individual muscle fiber will contract
to its full extent or not at all when stimulated above threshold.
8. Which metabolic pathway provides the quickest source of ATP for a short
burst of activity (e.g., a 100m sprint)?
A. Aerobic respiration
B. Creatine phosphate system
C. Anaerobic glycolysis
D. Beta-oxidation
Answer: B
Explanation: The phosphagen system (creatine phosphate) provides immediate ATP for
activities lasting about 10-15 seconds.
9. The structural classification of a neuron with one axon and many dendrites is:
A. Unipolar
B. Bipolar
C. Anaxonic
D. Multipolar
Answer: D
