The ATPase activity of the myosin head is dependent on:

1. Magnesium ions

2. Manganese ions

3. Calcium ions

4. Ferric ions

Prostaglandins have no role in 

1. inflammatory and allergic reactions

2. blood clotting 

3. smooth muscle contraction

4. conduction of nerve impulses.

If a stimulus, several times greater than the threshold stimulus is provided to a muscle

fibre, it will

1. Contract with a larger force

2. Contract with a smaller force

3. Contract with a same force

4. undergo tetany

A motor unit is best described as:

(1) All the nerve fibres and muscle fibres in a single muscle bundle

(2) One muscle fibre and its single nerve fibre

(3) A single motor neuron and all the muscle fibres that it innervates

(4) It is the neuron which carries the message from muscle to CNS

Assertion   :       Muscle as a whole doesn’t obey All or None law.

Reason      :       Each muscle fibre contracts maximally whenever it contracts.

The binding of troponin on actin Filaments actually unmasks the …..

1. Active site for Tropomyosin

2. Active site for ATP

3. Active site for Myosin

4. Active site for troponin

The binding of calcium to troponin actually indicates

1. Unmasking of Myosin binding site over meromyosin

2. Unmasking of Myosin binding site over actin

3. Unmasking of the actin-binding site over Myosin

4. Unmasking of actin-binding site over tropomyosin

Which of the following statements is incorrect?

1. A new ATP binds and cross-bridge is broken with the next cycle of contraction

2. The process of contraction continues till the calcium ions are pumped back to the sarcoplasmic cisternae and resulting in the unmasking of actin Filaments

3. The reaction time of the fibres can vary in different muscles

4. Both 1 and 3

Contractile unit of muscle is part of myofibril between

1.  Z-line and l-band

2.  Z-line and Z-line

3.  Z-line and A-band

4.  A-band and l-band 

The ion that must be present in an adequate amount for binding of cross-bridges with actin is 

1.  $C{a}^{+2}$

2.  $N{a}^{+}$

3.  $K^{+}$

4.  $M{g}^{+2}$