The brain is a complex organ responsible for controlling all aspects of physical and cognitive functioning. Operation requires a complex network of neurons and supporting cells called glial cells. The neurons function in sending and receiving signals while the supporting glial cells provide a structural framework, maintain homestasis and offer protection from harmful bacteria and drugs.
Neuron
The neuron is the core component of the nervous system with approximately 100 billion neurons in an average adult brain, according to "The Scientific American Book of the Brain." The brain and body communicate via electrical and chemical signaling between neurons. The electrical impulses travel along the neuron's axon and cause the release of chemicals called neurotransmitters at the end of an axon or synapse. The three types of neurons include sensory, motor and interneurons. Sensory neurons relay and process information from the external environment, motor neurons control body movement, and interneurons play an important role in connecting sensory and motor neurons.
Astrocyte
Astrocytes, also called astroglia, resemble stars and support glial cells that function in providing protection and maintenance of the brain's chemical environment. Astrocytes have structures called "end-feet" that form tight junctions around endothelial cells forming the blood-brain barrier. This barrier protects against drugs, bacteria and other nutrients and metabolites, allowing only certain molecules through. Astrocytes also function as a nutrient supply line for the brain as well as in controlling the chemical environment, such as in ion buffering or taking up excess neurotransmitters in the brain. Astrocytes also provide the highest amount of glycogen storage in the brain for use by the neurons.
Oligodendrocyte
Oligodendrocytes of the central nervous system play an important role in the structural framework of the brain and in increasing the conduction speed of neurons. Oligodendrocytes form what is called a myelin sheath around neurons. This sheath acts as an electrical insulator for neurons to increase the speed at which signals are sent between neurons. This allows the body to function much more quickly and efficiently in all its processes. Demyelinating diseases, such as multiple sclerosis, result from the loss of the myelin sheath around nerve cells, according to the Mayo Clinic.
Microglia
Microglia are the least numerous and smallest of the cell types in the brain, but still play a vital role in injury repair and cell debris and waste removal. They are similar to macrophages of the immune system in that they phagocytose (wrap around and eat) cell debris, waste and pathogens so the brain remains healthy and functioning properly. If an injury occurs, the cell congregate around the injured cells to clear the dead or dying cell.
Ependymal Cells
Ependymal cells support the neuroglial cells of the brain. The cells line the ventricles of the brain, which contain cerebrospinal fluid (CSF). Cerebrospinal fluid is a liquid that the brain "floats" in and serves as a protective cushion for the brain as well as a transport system for nutrients and wastes. The ependymal cells function in producing, circulating, and monitoring the CSF that flows through the ventriclular canals of the brain. They also serve as a permeable barrier between the CSF and the neurons, allowing only certain chemicals through.
