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# 13.18: Central Nervous System

Difficulty Level: At Grade Created by: CK-12
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The human brain. The "control center." What does it control?

Practically everything. From breathing and heartbeat to reasoning, memory, and language. And it is the main part of the central nervous system.

### Central Nervous System

The nervous system has two main divisions: the central nervous system and the peripheral nervous system (see Figure below ). The central nervous system (CNS) includes the brain and spinal cord (see Figure below ). You can see an overview of the central nervous system at this link: http://vimeo.com/2024719 .

The two main divisions of the human nervous system are the central nervous system and the peripheral nervous system. The peripheral nervous system has additional divisions.

This diagram shows the components of the central nervous system.

#### The Brain

The brain is the most complex organ of the human body and the control center of the nervous system. It contains an astonishing 100 billion neurons! The brain controls such mental processes as reasoning, imagination, memory, and language. It also interprets information from the senses. In addition, it controls basic physical processes such as breathing and heartbeat. The brain has three major parts: the cerebrum, cerebellum, and brain stem. These parts are shown in Figure below and described in this section. For a video of the parts of the brain and their functions, go to this link: http://www.teachers.tv/video/13838 .

You can also take interactive animated tours of the brain at these links:

In this drawing, assume you are looking at the left side of the head. This is how the brain would appear if you could look underneath the skull.

• The cerebrum is the largest part of the brain. It controls conscious functions such as reasoning, language, sight, touch, and hearing. It is divided into two hemispheres, or halves. The hemispheres are very similar but not identical to one another. They are connected by a thick bundle of axons deep within the brain. Each hemisphere is further divided into the four lobes shown in Figure below .
• The cerebellum is just below the cerebrum. It coordinates body movements. Many nerve pathways link the cerebellum with motor neurons throughout the body.
• The brain stem is the lowest part of the brain. It connects the rest of the brain with the spinal cord and passes nerve impulses between the brain and spinal cord. It also controls unconscious functions such as heart rate and breathing.

Each hemisphere of the cerebrum consists of four parts, called lobes. Each lobe is associated with particular brain functions. Just one function of each lobe is listed here.

#### Spinal Cord

The spinal cord is a thin, tubular bundle of nervous tissue that extends from the brainstem and continues down the center of the back to the pelvis. It is protected by the vertebrae , which encase it. The spinal cord serves as an information superhighway, passing messages from the body to the brain and from the brain to the body.

### Summary

• The central nervous includes the brain and spinal cord.
• The brain is the control center of the nervous system. It controls virtually all mental and physical processes.
• The spinal cord is a long, thin bundle of nervous tissue that passes messages from the body to the brain and from the brain to the body.

### Practice I

Use this resource to answer the questions that follow.

• http://www.hippocampus.org/Biology $\rightarrow$ Biology for AP* $\rightarrow$ Search: Central Nervous Systems
1. What is the central nervous system?
2. What is the role of the spinal cord?
3. Distinguish between white and grey matter.
4. Describe the main structures and functions of the mammalian brain.

### Review

1. Name the organs of the central nervous system.

2. Which part of the brain controls conscious functions such as reasoning?

3. What are the roles of the brain stem?

4. Tony’s dad was in a car accident in which his neck was broken. He survived the injury but is now paralyzed from the neck down. Explain why.

### Vocabulary Language: English Spanish

brain

brain

Central nervous system organ inside the skull; the control center of the nervous system.
brain stem

brain stem

Lowest part of the brain that connects the brain with the spinal cord; controls unconscious functions such as heart rate and breathing.
cerebellum

cerebellum

Part of the brain below the cerebrum; coordinates body movements.
cerebrum

cerebrum

Largest part of the brain; controls conscious functions such as reasoning and sight.
spinal cord

spinal cord

Thin, tubular bundle of nervous tissue that extends from the brainstem down the back to the pelvis; connects the brain with the peripheral nervous system.
vertebrae

vertebrae

(singular, vertebra): Repeating bony units that make up the vertebral column of vertebrates.

Feb 24, 2012

Jan 25, 2015