The nervous system is the body's communication and decision-making center, made up of the brain and spinal cord. The brain consists of three main parts: the cerebrum, cerebellum and brain stem. The two hemispheres of the cerebrum are connected to each other by a structure called the corpus callosum. Each area of the brain is responsible for different brain functions. This makes damage to one area often cause very specific problems. Cells that are responsible for processing information in the brain are called neurons.
The Cerebrum
The cerebrum is the largest of all areas of the brain. This highly folded top layer of the brain is made up of four lobes that are responsible for processing certain sensory information. The frontal lobe is the home of planning and reasoning. It controls emotions and is responsible for speech production. A lesion in this area is likely to make a patient more aggressive or violent. The temporal lobe processes auditory information and is essential for understanding language and helping in distinguishing smells. The parietal lobe, which processes pain and pressure, helps a person identify objects. The occipital lobe is a home of the visual cortex that allows a person to understand what he sees.
The Two Hemispheres and the Corpus Callosum
The cerebrum can be divided into the right and the left hemisphere that control the opposite sides of the body. This makes an injury to the left cortex often cause damage to the right side of the body, and vice versa. The two hemispheres are connected to each other by the corpus callosum. This structure enables communication between these areas. Patients with severe epilepsy have sometimes had this structure severed to prevent seizures from traveling from one hemisphere to another. Unfortunately, these patients often end up having great difficulties with tasks that require collaboration between hemispheres.
The Cerebellum
The cerebellum is responsible for fine-tuning movement. Evolutionary, it's assumed to be much older than the cerebrum. Just like the cerebrum, the cerebellum has two hemispheres. This area is associated with controlling and regulating movements and balance. It also tells the brain where the limbs are positioned. Damage to this area can lead to "jerky" muscle movements or even paralysis.
The Brain Stem
The brain stem is the oldest and most primitive part in the entire brain. It sits on top of the spinal cord and the cerebellum, controling such essential bodily functions as many reflexes, breathing, blood pressure, heart rate and alertness. Damage to this area can be life-threatening, because the brain stem is involved in so many vital functions to the body.
Neurons
The cells that make up the nervous system are called neurons and glia. Out of these, only neurons have the ability to send information to various parts of the body and to each other. This information is typically from one neuron to another with the help of neurotransmitters, but it can also be sent with the help of electrical signals. Both the structure and functions of these neurons change constantly and is caused by learning.
