Question

Short/ Long answer type questions.
Give the chemical events and changes that take place during muscle contraction.

Answer 1

The events that take place during muscle contraction are:

1. The contraction is initiated by the signal sent by CNS via motor neuron. At the axon terminal, acetylcholine is released that travels through the synaptic cleft and generates the action potential in the sarcolemma.

2. The impulse spread from sarcolemma to T-tubules to the sarcoplasmic reticulum.

3. As the muscle action potential travels along the sarcolemma and transverse tubule system, the calcium ion release channels open increasing its concentration. The calcium ions released combine with the muscle protein, troponin causing it to change the shape.

4. The globular head of myosin acts as ATPase that hydrolyses ATP. The energy generated is used by myosin to bind to the exposed active site on actin filament to form a cross bridge.

5. This pulls the actin filament towards the centre of A-band.

The changes that take place are:

1. The Z-line is pulled inwards thereby causing contraction.

2. The length of thin and thick filaments remains constant.

3. The H-zone shortens which reduces the length of I-band but retain the length of A-band