What Makes Gray and White Brain Matter?


Quick Answer

Gray brain matter is made of the bodies of neurons, while white matter is made up of the extensions of those cells, called axons, which connect the different neurons to one another. The axons in white matter are myelinated, which means they are insulated by biological materials, making them white.

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Full Answer

Grey matter has other components besides neuron cell bodies. Gray matter also contains accessory cells, capillaries and other types of nerve cell connections, including unmyelinated axons and dendrites. The gray matter covers the surface of the cerebellum and extends into the depths of the cerebrum and brainstem. It also extends into the depths of the spinal cord. Gray matter oversees motor control, sensory perception, memory, emotions and speech, and it actually has a gray-brown color in living brains because of the blood-bearing capillaries and the neurons themselves.

The myelin that makes white matter white is made up primarily of lipids. The properties of white matter allow the axons of the brain cells to transfer signals much more quickly than they could otherwise by allowing the signal to jump along the axons. These connections are very long and thin, and an adult human has about 100 miles of axons in the brain.

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