Answer
All neurons have a single cell body, but neurons can be classified into three types based on the criterion of number of processes that grow out of the perikaryon or cell body. Some cell bodies grow a single process ( often modified). These neurons are unipolar neurons. Neurons that grow two processes (an axon and a dendrite) are bipolar neurons. Multipolar neurons grow three or more processes ( an axon and several dendrites) from the perikaryon.
Work Step by Step
Unipolar neurons produce a single process--an axon that grows out of the cell body. There are no truly unipolar neurons of this type in humans, but they do occur in invertebrates. The so-called unipolar neuron of humans is really a pseudo-unipolar neuron. After the axon grows out of the soma, it divides into a peripheral branch and a central branch. This looks somewhat like an upper case "T" with the cross line of the "T" representing the two axonal branches, and the down stroke representing the soma.
Pseudo unipolar neurons are sensory neurons. The peripheral branch of the axon picks up peripheral sensations like temperature, and touch, and transmits them down the peripheral branch to the central branch. The central branch carries the stimuli into the spinal cord. Both branches are axons ; there are no dendrites here. Cell bodies usually lie in cranial or spinal nerve ganglia.
Bipolar neurons have grow two processes , an axon and a main dendrite. There are very few of this type of neuron in the body . They are found in the retina and olfactory mucosa.
Multipolar neurons grow one axon and two or more dendrites. This type of neuron is very plentiful in brain and spinal cord
