What is the brain?
The brain is a soft, spongy mass of tissue. It is protected by the bones
of the skull and three thin membranes called meninges. Watery fluid
called cerebrospinal fluid cushions the brain. This fluid flows through
spaces between the meninges and through spaces within the brain called
A network of nerves carries messages back and forth between the brain
and the rest of the body. Some nerves go directly from the brain to the
eyes, ears, and other parts of the head. Other nerves run through the
spinal cord to connect the brain with the other parts of the body.
Within the brain and spinal cord, glial cells surround nerve cells and
hold them in place.
The brain directs the things we choose to do (like walking and talking)
and the things our body does without thinking (like breathing). The
brain is also in charge of our senses (sight, hearing, touch, taste, and
smell), memory, emotions, and personality.
The three major parts of the brain control different activities:
* Cerebrum - The cerebrum is the largest part of the brain. It is at the
top of the brain. It uses information from our senses to tell us what is
going on around us and tells our body how to respond. It controls
reading, thinking, learning, speech, and emotions.
The cerebrum is divided into the left and right cerebral hemispheres,
which control separate activities. The right hemisphere controls the
muscles on the left side of the body. The left hemisphere controls the
muscles on the right side of the body.
* Cerebellum - The cerebellum is under the cerebrum at the back of the
brain. The cerebellum controls balance and complex actions like walking
* Brain Stem - The brain stem connects the brain with the spinal cord.
It controls hunger and thirst. It also controls breathing, body
temperature, blood pressure, and other basic body functions.