1. Which two types of filaments are arranged within a skeletal muscle sarcomere?
A.
Actin and myosin filaments
B.
Collagen and elastin filaments
C.
Keratin and tubulin filaments
D.
Cellulose and chitin filaments
Correct Answer:
Actin and myosin filaments
Explanation:
A sarcomere contains thin actin filaments and thick myosin filaments arranged for sliding during muscle contraction.
2. What is the basic contractile unit of a skeletal muscle fibre?
A.
Sarcomere
B.
Tendon
C.
Fascicle
D.
Motor neuron
Correct Answer:
Sarcomere
Explanation:
The sarcomere is the repeating unit between two Z lines where actin and myosin filaments are arranged to produce contraction.
3. In a sarcomere, thin actin filaments are attached to which structure?
A.
Z line
B.
H zone
C.
M line only
D.
A band
Correct Answer:
Z line
Explanation:
Actin filaments extend inward from the Z lines toward the centre of the sarcomere.
4. Which filament slides past the myosin filament during skeletal muscle contraction?
A.
Actin filament
B.
Collagen filament
C.
Keratin filament
D.
Elastin filament
Correct Answer:
Actin filament
Explanation:
During contraction, actin filaments slide inward past myosin filaments, bringing the Z lines closer together.
5. What happens to the length of the sarcomere when actin filaments slide inward?
A.
It becomes shorter
B.
It becomes longer
C.
It remains permanently unchanged
D.
It disappears completely
Correct Answer:
It becomes shorter
Explanation:
The inward sliding of actin between myosin filaments brings the Z lines closer, shortening the sarcomere.
6. Which band contains the entire length of the thick myosin filaments?
A.
A band
B.
I band
C.
H zone
D.
Z line
Correct Answer:
A band
Explanation:
The A band corresponds to the full length of the myosin filaments, including regions where they overlap with actin.
7. Which region of a sarcomere contains only thin actin filaments?
A.
I band
B.
A band
C.
H zone
D.
M line
Correct Answer:
I band
Explanation:
The I band is the region near the Z line that contains actin filaments without overlapping myosin filaments.
8. What happens to the I band during muscle contraction?
A.
It becomes shorter
B.
It becomes longer
C.
It remains the same length
D.
It changes into the A band
Correct Answer:
It becomes shorter
Explanation:
As actin slides inward and overlaps more with myosin, the region containing only actin becomes shorter.
9. Which region contains only thick myosin filaments in a relaxed sarcomere?
A.
H zone
B.
I band
C.
Z line
D.
Actin band
Correct Answer:
H zone
Explanation:
The H zone is the central part of the A band where only myosin filaments are present and actin does not overlap.
10. What happens to the H zone when a skeletal muscle contracts?
A.
It becomes narrower
B.
It becomes wider
C.
It remains unchanged in width
D.
It moves outside the sarcomere
Correct Answer:
It becomes narrower
Explanation:
During contraction, actin slides toward the centre and overlaps more of the myosin, reducing the width of the H zone.
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