During contraction of muscle fibers which of the following does not happen?

1. The length of the A band gets reduced

2. The attached actin Filaments are pulled towards the centre of A band

3. The Z line attached to actin Filaments is pulled inward

4. Shortening of sarcomere

Sliding Filament Theory states that

1. Contraction of muscle fibre takes place by the sliding of thin filaments over the thick filaments

2. Contraction of muscle fibre takes place by the sliding of thick filament over thin Filaments

3. Relaxation of muscle fibre takes place by the sliding of thick filament over thin filaments

4. Relaxation of muscle fibre takes place by the sliding of thin filament over thick filament

What masks the active sites for myosin head present on the actin myofilaments?
1. Light meromyosin
2. Heavy meromyosin
3. G – actin
4. Troponin

The cross-bridge formation actually involves

1. ATP hydrolysis

2. Binding of Myosin head to the exposed active sites for myosin

3. Both A and B

4. None of these

The role of calcium in muscle contraction is

1. to break the cross-bridges as a cofactor in the
hydrolysis of ATP

2. to bind with troponin, changing its shape so that
the actin filament is exposed

3. to transmit the action potential across the
neuromuscular junction

4. to spread the action potential through the T
tubules

When a skeletal muscle contracts

1. H-zone increases in length

2. A band decreases in length

3. I-bands get reduced

4. H-zone remains unaffected

Arrange the events during muscle contraction in correct order.

a. Acto-myosin complex synthesis

b. Release of neurotransmitter (acetylcholine) at the neuromuscular junction 

c. Pumping of ${\mathrm{Ca}}^{2+}$ into sarcoplasmic cisternae

d. Sliding of actin filaments over myosin

e. Release of ${\mathrm{Ca}}^{2+}$ into sarcoplasm

1. b, c, e, a d

2. e, b, a, d, c

3. b, e, a, d, c 

4. a, b, e, d, c

Which of the following is required for the breaking of cross-bridge during muscle contraction?

1. ATP and Ca⁺⁺

2.  ADP and Ca⁺⁺

3.  Only Ca⁺⁺

4.  ATP only

Which of the following statements about cross-bridges
is false?

1. They are composed of myosin
2. They bind to ATP after they attach to actin
3. They contain an ATPase
4. They split ATP before they attach to actin

The combination of a neuron and the muscle fiber it associates with is called a/an.

1. fascicle

2. motor end plate

3. motor unit

4. myoneural junction