Physiology of Muscle contraction:
Muscles contract to produce force, the actin and myosin filaments within the sarcomeres of muscle fibers bind to create cross-bridges and slide past one another, creating a contraction.
The events of muscle contraction:
- During a normal resting state of a muscle, the muscle membrane is in a polarized state, this occurs because:
- The interior of the muscle cell is negatively charged. It contains a large concentration of potassium ions.
- The exterior of the muscle cell is positively charged. It contains a large contraction of sodium ions.
- For a contraction to occur there must first be a stimulation of the muscle in the form of an impulse from a motor neuron. A motor neuron stimulates a number of muscle fibers within a muscle.
- The Nerve impulse reaches the muscle fibers of a Neuromuscular Junction, it stimulates a reaction in each sarcomere between the actin and myosin filaments. This reaction results in muscular contraction.
- When the muscle contraction is over, acetylcholine is destroyed by the acetyl cholinesterase.
- Now, Potassium ions move into the cell and sodium ions get out of the cell. ATP is re-synthesized allowing actin and myosin to maintain their strong binding state. This produces repolarization of the muscle membrane. Now the muscle is ready to contract again.