Fact Sheet For Grades 9-12
Cells of the Brain A neuron is made up of three basic parts: the cell body, or soma; branching dendrites that By Elizabeth A. Weaver II and Hillary H. Doyle receive signals from other neurons; and the axon, which sends signals out to surrounding The brain is a mosiac made up of different neurons through the axon terminal. When a cell types, each with their own unique neuron fires an action potential, electric and properties. The most common brain cells are chemical signals spread from the axon of one neurons and non-neuron cells called glia. The neuron to the dendrites of another neuron average adult human brain contains across a small gap called the synapse. (Read approximately 100 billion neurons, and just as our fact sheet on How Does the Brain Work? many—if not more—glia. Although neurons are to learn more.) the most famous brain cells, both neurons and glial cells are necessary for proper brain Glia function. Like neurons, glia are important cells of the nervous system. Scientists used to think that Neurons glia were like glue, only for holding the When you think of the brain, you probably neurons in place. The name “glia” is Latin for think of neurons. Neurons are the cells in the “glue.” However, we now know that glial cells brain that send and receive electrical and are not just brain glue. In fact, glia actively chemical signals. They are building blocks of participate in brain signaling, and are your brain, and transmit information to other necessary for the healthy function of neurons. neurons, muscles, and tissues throughout the body. They allow you to think, feel, move, and Unlike neurons, glial cells cannot fire action comprehend the world around you. potentials to communicate messages, but that does not mean they are inactive. Glia
Soma Axon
Synapse Myelin Sheath
Dendrites
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Cells of the Brain communicate to each other and to neurons the mess. This prevents the spread of buildup using chemical signals, and can even respond or debris in the brain, and protects the brain to many of the same chemicals that neurons from long term inflammation. Once the danger can, such as ions and neurotransmitters. This has passed, microglia go back to their resting means that glia can eavesdrop on the state, continuing to survey the brain. neurons, to help strengthen the messages that are passed between them. Research Highlight: Recently, scientists are discovering There are many types of glial cells in the brain. new roles for glial cells in disease. Here we will review three important glial cells Normally, glia protect and help known as oligodendrocytes, microglia, and neurons, but when they malfunction, they can cause serious damage. astrocytes. Animal studies have shown that inflammation caused by glia is Oligodendrocytes associated with many diseases such as Parkinson’s, Alzheimer’s, and A special type of glial cell known as an multiple sclerosis. This type of oligodendrocyte wraps around the axons of research is important because it neurons, making up what is known as the allows scientists to examine human diseases in animal models. As we myelin sheath. Like insulation around an continue to learn more about glia, we electrical wire, oligodendrocytes insulate the will be able to use this information to axon and help neurons pass electrical signals treat these diseases. at incredible speed and over long distances. Microglia Astrocytes Microglia are the immune cells of the central Astrocytes are star-shaped cells that nervous system. They move around within the surround neurons and support neuron brain and constantly communicate with other function. Astrocytes mainly help regulate glia. In a healthy adult brain, microglia are the brain’s environment. Astrocytes also constantly testing the environment for signs help neurons signal to other neurons by of trouble. For example, if an infection or passing chemicals from one neuron to disease causes neurons to die or become another. Although microglia are the primary damaged, these neurons will release chemical immune cells of the brain, “danger signals.” Microglia recognize these astrocytes can also help signals, and alert other nearby microglia of microglia when the brain potential danger. This causes the surrounding is in trouble. microglia to swarm to the dangerous area, where they begin to clean up
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