What carries out the work of the nervous system?

Nerves are the cables of the nervous system. Each nerve is packed with hundreds of wirelike cells called neurons, which carry electric signals to and from the brain. The brain and spinal cord form the central nervous system, and the nerves outside them are the peripheral nervous system.

Nerves branch from the brain and spinal cord, forming a treelike network that runs throughout the body.

Neurons work like wires, transmitting electric signals. When the neuron is resting, an electric charge builds up inside it. If triggered, a nerve impulse rushes to the end of the cell, where a chemical called a neurotransmitter passes the signal to the next neuron across a gap, or synapse.

All neurons are similar in structure to a motor neuron. The cell body contains the nucleus that controls the cell. Filaments called dendrites branch out from the cell body and pick up signals from other neurons. The nerve fiber, or axon, takes the signal and passes it on to other neurons, muscles, or glands.