Types of neurons

Based on the number of processes extending from the soma, neurons are classified as unipolar, bipolar and multipolar neurons. Figure 3.3 illustrates the types of neurons.

	Types of neurons.

As shown in figure 3.3, shows the unipolar, bipolar, and multipolar neurons. Unipolar neurons are sensory nerve cells with a single process connecting axon and dendrite. Most of the neurons conducting signals from skin to the brain and spinal cord are unipolar. The direction of conduction is from the dendrites to the axon. Bipolar neurons have a single axon and dendrite and hence are supposed to be primitive form of nerve cells. The direction of conduction in bipolar neuron is from the dendrite to the cell body and then to the axon. Multipolar neurons have many short dentrites and an axon. They are found throughout the central nervous system. As they are motor neurons, they constitute tracts of the brain. Multipolar neurons are further classified as Golgi type I and type II on the basis of their length and branching of the axons. Golgi type I neurons have long axons and few branches and they conduct excitation to some distance. Golgi type II neurons have short axons and multiple branches. They primarily extend excitation to nearby neurons.