Physiology of Muscle contraction

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:

1. 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.

1. 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.
2. 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.
3. When the muscle contraction is over, acetylcholine is destroyed by the acetyl cholinesterase.
4. 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.