Name: Vertebral Column
Uploaded: 2019-07-19
Duration: 3 min 21 s
Description: The vertebral column is present on the back. It is a hollow tube-like bone structure that comprises the spinal cord inside it. What exactly is it, and how do...

Question

Explain sliding filament theory of muscle contraction with neat sketches.

Accepted Answer

The sliding filament theory explains the contraction of muscles. As per this theory, when actin and myosin filaments slide towards each other; muscle contraction takes place.

A neural signal reaching to neuromuscular junction releases a neurotransmitter (Acetylcholine) which generates an action potential in the sarcolemma. Once the action potential is generated, calcium channels in the muscle cells open and allow the entry of calcium ions.

Increase of ${Ca}^{+ +}$ levels result in binding of calcium to troponin on the actin filament and bring about conformational changes. This removes the masking of active sites on myosin filaments.

Myosin a polymer of meromyosin has a head, arm and tail as its important parts. The head also called heavy meromyosin(HMM) utilizes the energy from ATP hydrolysis and binds with the active site on actin. This results in the formation of a cross-bridge between actin and myosin. This pulls the attached actin filaments towards the centre of 'A' band. The Z-line attached to actin are also pulled inwards, and contraction of muscle fibre happens.

Column I	Column II
A. Fast muscle fibres	(i) Myoglobin
B. Slow muscle fibres	(ii) Lactic acid
C. Actin filament	(iii) Contractile unit
D. Sarcomere	(iv) I-band

Explain sliding filament theory of muscle contraction with neat sketches.

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