The brain is divided into three main parts: the cerebrum, cerebellum and brainstem. Each part has a specific location and contains certain divisions. Within each part, there are nerve cells that give the tissue either a gray or white appearance and perform specific functions; however, each part does not function alone. The parts of the brain are connected to each other to allow the brain to be one functional unit. Injury to any one part leads to disruption in brain function and, therefore, behavior and cognition.
Location and Divisions
The cerebrum, or cerebral cortex, is the largest part of the brain, but the cortex is only a thin outer layer. The cerebrum is divided into two halves, or hemispheres. Each hemisphere is further divided into lobes: the frontal lobe, at the front; the parietal lobe, at the top; the temporal lobe, on both sides; and the occipital lobe at the back.
The cerebellum is a separate structure at the back of the brain. It is divided into hemispheres, as well, and each hemisphere is divided into lobes: the anterior, posterior and flocculonodular lobes.
The brainstem, located deep within the brain, and emerging out the bottom, is a structure that links the brain to the spinal cord and contains the cranial nerves. The brainstem is comprised of the midbrain, pons and medulla oblongata, according to Bryn Mawr College.
Nerve Cells
The fact that the outside of the brain is gray and the inside is white has to do with the parts of nerve cells. Nerve cells contain three parts: dendrites to pick up sensory input, a cell body and an axon to carry the electrical signal. The dendrites and cell body are gray, while the axon is typically white. The white color is created by myelin, a fatty substance that surrounds the axon to speed electrical signals. The outer layer of the cerebrum and cerebellum are gray because these areas contain only dendrites and cell bodies. The inside of the brain contains myelinated axon; therefore, the tissue is white. The brainstem contains both myelinated nerve cells and clusters of gray nerve cell bodies, according to Indiana University.
Function
Each lobe of the cerebrum is associated with a particular function: the frontal lobe controls movement, problem solving, reasoning, speech, and emotions. The parietal lobe controls movement planning, recognition, orientation, and sensory perception. The occipital lobe controls visual processing and the temporal lobe controls sensory perception, recognition, memory, hearing and speech. The cerebellum mediates movement coordination, balance and posture. The brainstem is responsible for the basic processes of life such as breathing, blood pressure and heart rate, according to Bryn Mawr College.
Connectivity
It is true that each brain region has a specific function, but in order to fulfill its function, additional information is required from other regions of the brain. Brain regions communicate through nerve fibers that travel to and from various regions. For example, the corpus callosum is a structure in the brain where nerve fibers connect the two cerebral hemispheres together, according to Bryn Mawr College.
Brain Injury
Brain injury can be from a tumor, stroke or head trauma. If one area of the brain is injured, it frequently causes functional difficulties in other areas due to the parts of the brain being highly connected. Injury to the cerebrum can result in difficulties in controlling movement, problem solving, reasoning, speech, and emotions. Injury to the brainstem is life threatening and can disrupt blood pressure, heart rate, breathing and swallowing, in addition to eye movement, speech, body movement and hearing, according to The Ohio State University Medical Center.
