Neural System

A neuron is a microscopic structure composed of three major parts namely cell body (soma), dendrites and axon. The cell body is the spherical part of the neuron that contains all the cellular organelles as a typical cell (except centriole) . The plasma membrane covering the neuron is called neurilemma and the axon is axolemma. The repeatedly branched short fibres coming out of the cell body are called dendrites, which transmit impulses towards the cell body.

The cell body and the dendrites contain cytoplasm and granulated endoplasmic reticulum called Nissl’s granules. An axon is a long fibre that arises from a cone shaped area of the cell body called the Axon hillock and ends at the branched distal end. Axon hillock is the place where the nerve impulse is generated in the motor neurons. The axon of one-neuron branches and forms connections with many other neurons.

An axon contains the same organelles found in the dendrites and cell body but lacks Nissl’s granules and Golgi apparatus. Figure . Neuron Nucleus with nucleolus Soma Trigger zone Axon hillock Initial segment Direction of signal transmission Synaptic knobs