<P> The structure of a neuron is seen to consist of two separate functional regions, or compartments--the cell body together with the dendrites as one region, and the axonal region as the other . Nissl bodies of the soma and dendrites, where protein is synthesised is absent in the axonal region which includes the axon hillock . </P> <P> The axonal region or compartment, includes the axon hillock, the initial segment, the rest of the axon, and the axon telodendria, and axon terminals . It also includes the myelin sheath . The Nissl bodies that produce the neuronal proteins are absent in the axonal region . Proteins needed for the growth of the axon, and the removal of waste materials, need a framework for transport . This axonal transport is provided for in the axoplasm . </P> <P> The axon hillock is the area formed from the cell body of the neuron as it extends to become the axon . It precedes the initial segment . The received action potentials that are summed in the neuron are transmitted to the axon hillock for the generation of an action potential from the initial segment . </P> <P> The axonal initial segment (AIS) is a structurally and functionally separate microdomain of the axon . One function of the initial segment is to separate the main part of an axon from the rest of the neuron; another function is to help initiate action potentials . Both of these functions support neuron cell polarity, in which dendrites (and, in some cases, soma) of a neuron receive input signals and the neuron's axon provides output signals . </P>

Region of cell body from which axon originates