Question

summarize muscle contraction

be thorough but also keep it short please, its going on twitter

Answer 1

Muscle contraction occurs when actin and myosin filaments slide past each other. This process is done by cross-bridges formation which extend from the myosin filaments and cyclically interact with the actin filaments as ATP is hydrolysed.

Muscle contraction is based on the sliding filament theory which can be broken down into four distinct stages:

1. Muscle activation: The motor neuron stimulates an action potential to pass through a neuron to the neuromuscular junction which stimulates the sarcoplasmic reticulum to release calcium into the muscle cell.

2. Muscle contraction: Calcium accumulates in the muscle cell binding to troponin causing actin and myosin to bind. The actin and myosin cross bridges bind and contract using ATP as an energy source.

3. Recharging: ATP is regenerated allowing actin and myosin to maintain their strong binding state so as to maintain the contraction.

4. Relaxation: When stimulation of the nerve stops, Calcium is pumped back into the sarcoplasmic reticulum breaking the link between actin and myosin. Thus actin and myosin return to their unbound state causing the muscle to relax. Alternatively relaxation also occurs when ATP is no longer available to provide energy for contraction.

Felt great to answer. Good luck!