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Brain and Nervous System

What Does the Brain Do?

The brain controls what we think and feel, how we learn and remember, and the way we move and talk. But it also controls things we're less aware of — like the beating of our hearts and the digestion of our food.

Think of the brain as a central computer that controls all the body's functions. The rest of the nervous system is like a network that relays messages back and forth from the brain to different parts of the body. It does this via the spinal cord, which runs from the brain down through the back. It contains threadlike nerves that branch out to every organ and body part.

When a message comes into the brain from anywhere in the body, the brain tells the body how to react. For example, if you touch a hot stove, the nerves in your skin shoot a message of pain to your brain. The brain then sends a message back telling the muscles in your hand to pull away. Luckily, this neurological relay race happens in an instant.

What Are the Parts of the Nervous System?

The nervous system is made up of the central nervous system and the peripheral nervous system:

  • The brain and the spinal cord are the central nervous system.
  • The nerves that go through the whole body make up the peripheral nervous system.

The human brain is incredibly compact, weighing just 3 pounds. It has many folds and grooves, though. These give it the added surface area needed for storing the body's important information.

The spinal cord is a long bundle of nerve tissue about 18 inches long and 1/2-inch thick. It extends from the lower part of the brain down through spine. Along the way, nerves branch out to the entire body.

Both the brain and the spinal cord are protected by bone: the brain by the bones of the skull, and the spinal cord by a set of ring-shaped bones called vertebrae. They're both cushioned by layers of membranes called meninges and a special fluid called cerebrospinal fluid. This fluid helps protect the nerve tissue, keep it healthy, and remove waste products.

What Are the Parts of the Brain?

The brain is made up of three main sections: the forebrain, the midbrain, and the hindbrain.

The Forebrain

The forebrain is the largest and most complex part of the brain. It consists of the cerebrum — the area with all the folds and grooves typically seen in pictures of the brain — as well as some other structures under it.

The cerebrum contains the information that essentially makes us who we are: our intelligence, memory, personality, emotion, speech, and ability to feel and move. Specific areas of the cerebrum are in charge of processing these different types of information. These are called lobes, and there are four of them: the frontal, parietal, temporal, and occipital lobes.

The cerebrum has right and left halves, called hemispheres. They're connected in the middle by a band of nerve fibers (the corpus callosum) that lets them communicate. These halves may look like mirror images of each other, but many scientists believe they have different functions:

  • The left side is considered the logical, analytical, objective side.
  • The right side is thought to be more intuitive, creative, and subjective.

So when you're balancing your checkbook, you're using the left side. When you're listening to music, you're using the right side. It's believed that some people are more "right-brained" or "left-brained" while others are more "whole-brained," meaning they use both halves of their brain to the same degree.

The outer layer of the cerebrum is called the cortex (also known as "gray matter"). Information collected by the five senses comes into the brain to the cortex. This information is then directed to other parts of the nervous system for further processing. For example, when you touch the hot stove, not only does a message go out to move your hand but one also goes to another part of the brain to help you remember not to do that again.

In the inner part of the forebrain sits the thalamus, hypothalamus, and