Question

1. Calcium ions bind to ___________ on the thin filament, which leads to the exposure of myosin binding sites on actin.

A.) tropomyosin
B.) titin
C.) dystrophin
D.) troponin
E.) actin

2. Release of ACh

A.) decreases the positive charge on the sarcolemma.
B.)reduces the exposure of actin binding sites.
C.) lowers the threshold of the muscle fiber.
D.)increases permeability of the motor end plate to sodium ions.
E.) decreases the release of Ca2+ from the sarcoplasmic reticulum.

3. All of the following are needed to produce a skeletal muscle contraction, except __________.
       
A.) calcium ions in the sarcoplasm
B.) sodium ions entering the cell at the NMJ
C.) acetylcholine in the synaptic cleft
D.) ATP
E.) acetylcholinesterase activity

4. Stronger skeletal muscle contractions may be brought about by ____.

A.) increasing resting sarcomere length to allow only slight overlap between thick and thin filaments.
B.) recruiting more motor units
C.) stimulating the smallest muscle fibers
D.) decreasing the frequency of stimulation so the fibers can recover between cycles and produce more ATP.

5. All of the following occur during muscle contraction, except ____________________.

A.) the A band widens
B.) the I bands narrow
C.) the sarcomere shortens
D.) the H zone narrows
E.) the Z discs move towards the M line

Answer 1

1. Troponin

2. Increases permeability of motor end plate to sodium ion

3. Acetylcholine estrase activity

• Acetylcholine estrase is enzyme present in synaptic cleft. It metabolize Acetylcholine.

4. Recruting more motor unit

5. A band widens

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