ABSTRACT
A neuron with a single neurite is unipolar, one with two neurites is bipolar while a neuron with three or more neurites is said to be multipolar. Hence neurons are classified either according to morphology, function or by their neurotransmitters, and the assumption is that all neurons falling into a single class have similar functions. Neurons can also be classified on the basis of the lengths of their axons. Projection neurons have long axons which extend way beyond the region of the nervous system in which their cell body resides. Finally, neurons can be classified according to the neurotransmitters which they secrete. Moreover, there is often a clear correlation between neuron morphology and neurotransmitter. Estimates of the number of neurons in the nervous system can be made by statistical analysis of cell counts in thin tissue sections viewed under light microscope.
