Excitation Contraction Coupling

Q.

What is the junction between the sarcolemma of muscle fibre and the motor neuron called?

Q. The ion required for muscle contraction and nerve impulse transmission is:

1. ${\mathrm{Ca}}^{2+}$
2. ${\mathrm{Mg}}^{2+}$
3. ${\mathrm{Na}}^{+}$
4. ${\mathrm{Ca}}^{2+}$ and ${\mathrm{Na}}^{+}$

Q.

Why does one experience a muscle spasm?

Q. Name the ion responsible for unmasking of active sites for myosin for cross-bridge activity during muscle contraction

1. Sodium.
2. Potassium.
3. Calcium
4. Magnesium

Q.

When do muscle fibres contract?

Q. The ion required for muscle contraction and nerve impulse transmission is:

1. ${\mathrm{Ca}}^{2+}$
2. ${\mathrm{Mg}}^{2+}$
3. ${\mathrm{Na}}^{+}$
4. ${\mathrm{Ca}}^{2+}$ and ${\mathrm{Na}}^{+}$

Q. What will happen to a muscle fibre when it is constantly acted upon by stimuli?

1. The muscle stops contracting
2. Tetanic contraction
3. The duration of response decreases
4. None of the above

Q. At the neuromuscular junction, nerve impulses are carried across the synaptic cleft by neurotransmitters.

1. True
2. False

Q. During muscle contraction, which of the following shortens?
(i) A band
(ii) I band
(iii) Sarcomere

1. i and ii
2. ii and iii
3. i and iii
4. i, ii, and iii

Q. In the resting muscle fibre, tropomyosin partially covers

1. Actin binding sites on myosin
2. Myosin binding sites on actin
3. Calcium binding sites on troponin
4. Calcium binding sites on actin

Q. Select the correct option:
i) Muscle contraction takes place by sliding of thick filaments over thin filaments.
ii) When the neural signal reaches the neuromuscular junction, it releases acetylcholine, which helps generate an action potential in the muscle fibre.
iii) Muscle contraction begins by a signal sent by the peripheral nervous system by a motor neuron.

1. Only i is correct
2. Only ii and iii are correct
3. Only ii is correct
4. All are correct