http://www.ck12.org Chapter 1. Human Biology
1.41 Nerve Cells and Nerve Impulses
- Describe neurons and explain how they carry nerve impulses.
What do nerve cells look like?
Note that like most other cells, these nerve cells have a nucleus. They also have other organelles. However, the long,
threadlike extensions of the nerve cells are unique. This is where the nerve impulses are transmitted.
Neurons and Nerve Impulses
The nervous system is made up of nerves. Anerveis a bundle of nerve cells. A nerve cell that carries messages is
called aneuron(Figure1.73). The messages carried by neurons are callednerve impulses. Nerve impulses can
travel very quickly because they are electrical impulses.
Think about flipping on a light switch when you enter a room. When you flip the switch, the electricity flows to the
light through wires inside the walls. The electricity may have to travel many meters to reach the light, but the light
still comes on as soon as you flip the switch. Nerve impulses travel just as fast through the network of nerves inside
the body.
What Does a Neuron Look Like?
A neuron has a special shape that lets it pass signals from one cell to another. A neuron has three main parts (Figure
1.73):
- The cell body.