Chapter 20

Controlling the Body

20.1 Lesson 20.1: Nervous System

Lesson Objectives

• Identify the functions of the nervous system.


• Describe neurons and explain how they carry nerve impulses.


• Describe the structures of the central nervous system.


• Outline the divisions of the peripheral nervous system.

Check Your Understanding

• If groups of cells are called tissues and groups of tissues are called organs, what are
  groups of organs called?


• What are examples of human organ systems?


• Which organ system controls all the others?

Introduction

Groups of organs called organ systems. Examples of human organ systems are skeletal,
digestive, and respiratory systems. The nervous system controls all the others.

Michael was riding his scooter when he hit a hole in the sidewalk and started to lose control.
He thought he would fall, but in the blink of an eye, he shifted his weight and regained his
balance. His heart was pounding, but at least he didn’t get hurt. How was he able to react
so quickly? Michael can thank his nervous system for that (Figure20.1).