http://www.ck12.org Chapter 1. Human Biology
1.40 Nervous System
- Explain the functions of the nervous system.
What body system helps you learn?
As these girls are studying, many processes are taking place. Their eyes have to take in the words on the page, and
their brains have to process the meaning of the words. The brain also has to assimilate the knowledge so it can be
retrieved at a later time. All these processes are controlled by the nervous system.
Introduction to the Nervous System
Michelle was riding her scooter when she hit a hole in the street and started to lose control. She thought she would
fall, but, in the blink of an eye, she shifted her weight and kept her balance. Her heart was pounding, but at least she
didn’t get hurt. How was she able to react so quickly? Michelle can thank her nervous system for that (Figure1.72).
Thenervous system, together with theendocrine system, controls all the otherorgan systems. Controlling muscles
and maintaining balance are just two of its roles. The nervous system also lets you:
- Sense your surroundings with your eyes and other sense organs.
- Sense the environment inside of your body, including temperature.
- Control your internal body systems and keep them in balance.
- Prepare your body to fight or flee in an emergency.
- Use language, think, learn, and remember.
The nervous system works by sending and receiving electrical signals. The signals are carried bynervesin the body,
similar to the wires that carry electricity all over a house. For example, when Michelle started to fall off her scooter,
her nervous system sensed that she was losing her balance. It responded by sending messages to muscles in her
body. Some muscles tightened while others relaxed. As a result, Michelle’s body became balanced again.