Anatomy and Physiology I - Exam 3 (Muscular and Nervous Systems)
Questions and Answers and Explanations | Latest Chamberlain
1. Which of the following is the structural and functional unit of skeletal muscle
contraction?
A. Myofibril
B. Sarcolemma
C. Sarcomere
D. Sarcoplasmic reticulum
Answer: C
Explanation: The sarcomere is the segment between two Z-lines and is considered the
basic functional unit of a muscle fiber.
2. What neurotransmitter is released at the neuromuscular junction to initiate
muscle contraction?
A. Dopamine
B. Norepinephrine
C. Serotonin
D. Acetylcholine
Answer: D
,Explanation: Acetylcholine (ACh) is the specific neurotransmitter that crosses the synaptic
cleft at the neuromuscular junction.
3. During muscle contraction, calcium ions bind to which protein to expose
binding sites?
A. Myosin
B. Tropomyosin
C. Troponin
D. Actin
Answer: C
Explanation: Calcium binds to troponin, which then causes tropomyosin to shift,
uncovering the active sites on actin.
4. Which connective tissue layer surrounds an entire individual muscle?
A. Endomysium
B. Perimysium
C. Epimysium
D. Aponeurosis
Answer: C
Explanation: The epimysium is the outermost layer of dense irregular connective tissue
that encircles the whole muscle.
,5. What is the role of Acetylcholinesterase (AChE) in the neuromuscular
junction?
A. To enhance the effect of Acetylcholine
B. To bind to the postsynaptic receptors
C. To transport Calcium back into the SR
D. To break down Acetylcholine to stop the signal
Answer: D
Explanation: AChE breaks down ACh into choline and acetic acid, effectively ending the
muscle stimulation.
6. What happens to the I-bands and H-zones during a muscle contraction
according to the sliding filament model?
A. They stay the same length
B. They lengthen
C. They shorten or disappear
D. Only the H-zone lengthens
Answer: C
Explanation: As actin is pulled toward the M-line, the I-bands and H-zones narrow and can
disappear, while the A-band length remains constant.
, 7. Which energy source provides the first few seconds of energy for muscle
contraction?
A. Glucose
B. Creatine phosphate
C. Glycogen
D. Lactic acid
Answer: B
Explanation: Creatine phosphate provides a very rapid source of ATP for about the first 15
seconds of activity.
8. In a resting neuron, the concentration of which ion is higher outside the cell
than inside?
A. Potassium (K+)
B. Proteins
C. Sodium (Na+)
D. Phosphate
Answer: C
Explanation: The sodium-potassium pump maintains a higher concentration of Sodium
(Na+) in the extracellular fluid.
Questions and Answers and Explanations | Latest Chamberlain
1. Which of the following is the structural and functional unit of skeletal muscle
contraction?
A. Myofibril
B. Sarcolemma
C. Sarcomere
D. Sarcoplasmic reticulum
Answer: C
Explanation: The sarcomere is the segment between two Z-lines and is considered the
basic functional unit of a muscle fiber.
2. What neurotransmitter is released at the neuromuscular junction to initiate
muscle contraction?
A. Dopamine
B. Norepinephrine
C. Serotonin
D. Acetylcholine
Answer: D
,Explanation: Acetylcholine (ACh) is the specific neurotransmitter that crosses the synaptic
cleft at the neuromuscular junction.
3. During muscle contraction, calcium ions bind to which protein to expose
binding sites?
A. Myosin
B. Tropomyosin
C. Troponin
D. Actin
Answer: C
Explanation: Calcium binds to troponin, which then causes tropomyosin to shift,
uncovering the active sites on actin.
4. Which connective tissue layer surrounds an entire individual muscle?
A. Endomysium
B. Perimysium
C. Epimysium
D. Aponeurosis
Answer: C
Explanation: The epimysium is the outermost layer of dense irregular connective tissue
that encircles the whole muscle.
,5. What is the role of Acetylcholinesterase (AChE) in the neuromuscular
junction?
A. To enhance the effect of Acetylcholine
B. To bind to the postsynaptic receptors
C. To transport Calcium back into the SR
D. To break down Acetylcholine to stop the signal
Answer: D
Explanation: AChE breaks down ACh into choline and acetic acid, effectively ending the
muscle stimulation.
6. What happens to the I-bands and H-zones during a muscle contraction
according to the sliding filament model?
A. They stay the same length
B. They lengthen
C. They shorten or disappear
D. Only the H-zone lengthens
Answer: C
Explanation: As actin is pulled toward the M-line, the I-bands and H-zones narrow and can
disappear, while the A-band length remains constant.
, 7. Which energy source provides the first few seconds of energy for muscle
contraction?
A. Glucose
B. Creatine phosphate
C. Glycogen
D. Lactic acid
Answer: B
Explanation: Creatine phosphate provides a very rapid source of ATP for about the first 15
seconds of activity.
8. In a resting neuron, the concentration of which ion is higher outside the cell
than inside?
A. Potassium (K+)
B. Proteins
C. Sodium (Na+)
D. Phosphate
Answer: C
Explanation: The sodium-potassium pump maintains a higher concentration of Sodium
(Na+) in the extracellular fluid.
