Structure

The brain is composed of four major sections:

The Cerebrum

The cerebrum is the largest portion of the brain and located in the uppermost section of the brain. The cerebrum may be divided into two sections separated by a groove (the great longitudinal fissure). Each half is referred to as a cerebral hemisphere. The right hemisphere controls the left side of the body while the left hemisphere controls the right side of the body. The corpus callosum connects the hemispheres at the bottom and delivers messages from one half of the brain to the other. Each hemisphere is further divided into distinct regions, called lobes.

The outer surface of the brain, referred to as the cerebral cortex, appears wrinkled and grayish brown in color. The outermost layer of the cerebral cortex consists of gray matter (so named because of its appearance). The gray matter is made of the nerve cells that control brain activity. Below the surface, white matter (which appears white in color) carries information between the nerve cells in the brain and the spinal cord.

The Cerebellum

The second largest portion of the brain is the cerebellum. The cerebellum occupies the back portion of the brain and is attached to the brain stem. The cerebellum initiates muscular movement, coordinates and refines the movement, and aids in maintaining balance in the body.

The Diencephalon (Interbrain)

Composed of many smaller structures, the interbrain, receives most of the information from the senses (sight, touch, hearing, taste) with the exception of the sense of smell. This information is processed in the interbrain and sent to the appropriate portion of the cerebral cortex.

The Brain Stem

The brain stem acts as a pathway for information being transmitted between the brain and the spinal cord. The brain stem is the bottom most portion of the brain. It is also the control center for basic body functions, such as blood pressure, heart rate and respiration (breathing).