Question

Why is grey matter on the surface of the brain but sits inside the spinal cord?

Answer 1

Why is grey matter on the surface of the brain but sits inside the spinal cord?

White matter and grey matter are important components of CNS including grey matter and white matter. Grey matter usually looks like pinkish-grey color in living brain. Grey matter is rich with cell bodies, dentrites, axon terminals of neurons and all the synapses are! Grey matter mostly contains neuron cell bodies and non-neuron brain cells called glial cells also lack myelin content thereby remains normal grey color appearance and so called as 'grey matter'. These glial cells transport glucose into the brain and they provide nutrients and energy to neurons. They also helps in scavenging excess chemicals and may even affect the intensity of the neuronal communications. White matter contains axons which helps to connect different parts of grey matter. It has long axon tracts and spindly appendages of some brain cells which transmit the electrical signals called neurons. Axons in white matter is wrapped in fatty layer called myelin which helps to conduct signals quickly. Fatty layer of axon gives the white color appearance given the term 'White matter'.

In brain, white matter is buried deep inside whereas the grey matter is on the brain's surface, or cortex. The reverse is seen is spinal cord, in which grey matter at its core with insulating white matter is on the surface. This is because that the spinal cord involves in transmitting nerve impulses to and from the rest of the body. The white matter on the surface of the spinal cord helps in faster transmission