Question

Explain the important steps of sliding filament theory of muscle contraction.

Answer 1

(i) Central Nervous system initiate muscle contraction via motor neuron. 

(ii) Motor neuron–stimulate muscle fibre→secrete neurotransmitter→generate action potential in the sarcolemma→ Release of Ca²⁺ in sarcoplasm Ca²⁺ binds with troponin→ Unmask active site Myosin head binds to actin at active site and form cross bridge using ATP. → Pulls the actin filament towards the centre of 'A' band→Z lines also pulled thereby shortening of sarcomere i.e., contraction. I band get reduced, where the A band retain the length. 

During relaxation: 

Cross bridge between actin and myosin break→ Ca²⁺ pumped back into sarcoplasmic cisternae→ Actin filament slide out of 'A' band and length of I band increases.