<P> Connecting each of the hemispheres is the corpus callosum as well as several additional commissures . One of the most important parts of the cerebral hemispheres is the cortex, made up of gray matter covering the surface of the brain . Functionally, the cerebral cortex is involved in planning and carrying out of everyday tasks . </P> <P> The hippocampus is involved in storage of memories, the amygdala plays a role in perception and communication of emotion, while the basal ganglia play a major role in the coordination of voluntary movement . </P> <P> This differentiates the central nervous system from the peripheral nervous system, which consists of neurons, axons and Schwann cells . Oligodendrocytes and Schwann cells have similar functions in the central and peripheral nervous system respectively . Both act to add myelin sheaths to the axons, which acts as a form of insulation allowing for better and faster proliferation of electrical signals along the nerves . Axons in the central nervous system are often very short (barely a few millimeters) and do not need the same degree of isolation as peripheral nerves do . Some peripheral nerves can be over 1m in length, such as the nerves to the big toe . To ensure signals move at sufficient speed, myelination is needed . </P> <P> The way in which the Schwann cells and oligodendrocytes myelinate nerves differ . A Schwann cell usually myelinates a single axon, completely surrounding it . Sometimes they may myelinate many axons, especially when in areas of short axons . Oligodendrocytes usually myelinate several axons . They do this by sending out thin projections of their cell membrane which envelop and enclose the axon . </P>

A basic nerve cell in the central nervous system is called a(n
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