Your body and brain communicate with each other through nerve cells called neurons arranged throughout the body. These neurons function through the generation and conduction of electrical impulses. Without the nervous system, you would not be able to think, sense, or even move. On a very basic level, here's how it works.

1. Cell membrane pumps and selective permeability cause chlorine and sodium ions to build up outside the cell, and potassium ions and protein anions build up inside.

2. Buildup of ions creates both a concentration gradient and an electrical charge gradient across the cell membrane, creating a voltage of about -60 mV.

3. Depolarization consists of cell membrane channels opening and allowing sodium ions to flow in, changing the membrane potential to about +55 mV.

4. Wave of depolarization diffuses over cell body and sets off an electrical potential that is conducted down the axon to the bulbs, where it activates chemicals that diffuse to the next neuron.

5. Potassium ions flow out of the cell in order to return membrane to resting potential of -60 mV.

Wikipedia

This image shows the progression of a nerve impulse over time. When a stimulus causes depolarization (flow of ions) in the cell body, the change in voltage must be large enough to activate an action potential, which then is conducted down the axon, as previously described. The repolarizaton period involves the potassium ions flowing out of the cell, which returns the cell to its resting potential. During the refractory period, the cell cannot receive or produce impulses.

© 2005 Ana Marx