The human brain functions as the control center for the body. As a part of the nervous system, the brain receives, processes and responds to information gathered through the sensory experiences of the body. It regulates the operation of other vital organs, generates thoughts and emotions, and activates hunger and sleep drives. Though each of the various components of the brain perform specific tasks, they work together to make the complexities of human life possible.
Cerebrum
The cerebral cortex, or cerebrum, is the largest part of the brain and is responsible for higher brain functions like reasoning, memory and speech. Its surface is characterized by deep folds, which allow for a greater number of brain cells to fit in the contained space. The cerebrum is divided into right and left hemispheres that are connected by a bundle of axons called the corpus callosum. Each of these hemispheres is also subdivided into four sections, or lobes. The front section, called the frontal lobe, handles reasoning, emotion and problem solving. On the center bottom, the temporal lobe deals with perception of sound, memory and speech. The top section of the hemisphere, the parietal lobe, is associated with movement and orientation. And the back section, the occipital lobe, processes visual stimuli.
Cerebellum
Like the cerebrum, the cerebellum is divided into two hemispheres and has a highly wrinkled surface. It sits tucked under the occipital lobe of the cerebrum. Biologists believe the cerebellum to be a much older part of the brain, as many species that evolved before humans, such as reptiles, have fully evolved cerebellums. This section of the brain controls balance and posture. It also helps to coordinate voluntary motions like walking and talking as well as learned motor skills such as riding a bicycle.
Limbic System
Hidden inside the cerebral cortex at the center of the brain is the limbic system, of which the thalamus, hypothalamus, amygdala and hippocampus are parts. The thalamus is a pathway of gray matter that transports information from sensory organs, such as the eyes and ears, to the cerebral cortex for processing. The hypothalamus regulates bodily drives, such as homeostasis, hunger and thirst. The amygdala controls emotion and fear and is also involved in memory. And, the hippocampus controls learning by converting short-term memories to permanently held information.
Brain Stem
The brain stem regulates many involuntary bodily functions like heart rate, breathing and blood pressure. It is located underneath the limbic system and extends downward under the cerebellum. It is made up of three sections, which are called the midbrain, the pons and the medulla. The midbrain at the top end of the brain stem is involved in visual and auditory reflexes and voluntary motor function. The pons deals with sleep and levels of consciousness and the medulla, at the tail end of the brain stem, controls heart rate and respiration.
The Neuron
The brain is composed of billions of nerve cells called neurons. These cells transport electrochemical information from one to another. Branching off of the soma, the body of the cell that contains the nucleus, are extensions called dentrites. The dentrites receive electrochemical messages from other neurons that pass through the soma of the neuron. The neuron then passes the signal along to more cells via a special extension called an axon. The cells do not actually touch each other, but instead send the information through a space called a synapse.
