7th Grade Science Student ebook

UNIT 6 THE HUMAN BODY

Figure 18.1: The parts of a neuron.

central nervous system - the

control center of the body that

includes the brain and spinal cord.

peripheral nervous system -

consists of nerves that connect all

areas of the body to the central

nervous system.

nerve impulse - a wave of

electrical activity transmitted

between neurons.

18.1 The Nervous System

Which body system allows you to see and hear? Which body system keeps your other
systems working properly? You are right if you guessed your nervous system. In this
section, you will learn about the components of the nervous system and how signals
are transmitted in your body.

Parts of the human nervous system

Central and

peripheral

nervous systems

There are two major divisions of the

nervous system. The central nervous

system is your body’s command

center. It includes the brain and

spinal cord. The peripheral nervous

system consists of nerves that

connect all areas of the body to the

central nervous system. You can

think of the peripheral nervous

system as the “information

highway” of your nervous system.

Neurons and

nerve impulses

Your nervous system is made of

hundreds of billions of specialized

cells called neurons. A neuron has

three parts: the cell body, a long stalk

called the axon, and finger-like

projections called dendrites (Figure 18.1).

Neurons send signals called nerve

impulses throughout your body. A nerve

impulse is wave of electrical and chemical

activity transmitted between neurons.