The body of a nerve cell (neuron) has many long, snaking arms calked dendrites and axons, which reach out to other cells, forming a neural net.
Travels along one of the nerve cell's long axons.
Wave of electricity
The impulse is a wave of electrical charge particles called ions.
When no impulse us being transmitted, the ions (red spheres) outside the membrane of the nerve cell are positively charged and those inside it are negatively charged. The arrangement "polarizes" (charges) the membrane.
When an impulse arrives, positive ions rush into the neuron. So many positive ions rush in that the membrane us depolarized. The inside if the cell us now positive compared to the outside.
Ions flow in the opposite direction, restoring the balance, and the electrical charge stimulates the next areas of membrane, passing the impulse on.
Crossing the Gap
An electric impulse arrives at a junction between nerve cells. It triggers the release of chemicals called neurotransmitters (red spheres), which cross the tiny gap between the nerve cells.
The neurotransmitters slot into recesses in channels.