Making connections
The brain and the rest of the nervous system are composed of many different types of cells, but the primary functional unit is a cell called the neuron. All sensations, movements, thoughts, memories, and feelings are the result of signals that pass through neurons.
Neurons consist of three parts:
- The cell body containing the nucleus, where most of its molecules for proper functioning are manufactured.
- Dendrites extend out from the cell body like the branches of a tree and receive messages from other nerve cells that are passed on to the cell’s body.
- Some signals travel away from the cell body, down an axon to another neuron, a muscle cell, or cells in some other organ.
The neuron is surrounded by many support cells, some of which wrap around the axon to form an insulating sheath, making nerve signals travel faster and farther. Axons may be very short and carry signals only a hair’s width away, or are very long, carrying messages way down the spinal cord.
