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11.40: Nervous System

Difficulty Level: At Grade Created by: CK-12
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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 (Figure below).

Staying balanced when riding a scooter requires control over the body’s muscles. The nervous system controls the muscles and maintains balance.

The nervous system, together with the endocrine system, controls all the other organ 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.
  • Think, learn, remember, and use language.

The nervous system works by sending and receiving electrical signals. The signals are carried by nerves in 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.


  • endocrine system:
  • nerve:
  • nervous system: Body system that sends electrical messages throughout the body; controls all other body systems.
  • organ system: Groups of organs that work together to perform a specific task.


  • The nervous system sends electrical messages throughout the body and controls all other body systems.
  • The nervous system allows you to think, learn, sense your surroundings, and control your internal body systems.


Use the resource below to answer the questions that follow.

  1. What are the major organs of the nervous system?
  2. What does the somatic nervous system do? Why is a system like this useful to organisms?
  3. What does the autonomic nervous system do? How does it differ from the somatic nervous system?


  1. What are some functions of the nervous system?
  2. What type of signals does the nervous system send?

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endocrine system

System of glands that secrete hormones into the bloodstream.


Bundle of nerve cells.

nervous system

Body system that sends electrical messages throughout the body; controls all other body systems.

organ system

Groups of organs that work together to perform a specific task.

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Difficulty Level:
At Grade
7 , 8
Date Created:
Nov 29, 2012
Last Modified:
Aug 30, 2016
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