Nerves and muscles are called as excitable cells. Neuron is the structural and functional unit of nervous system. The structure of neuron consists of the cell body and axon along with dendrites. The cell body consists of nucleus endoplasmic reticulum, ribosomes and Golgi complex. The cell body consists of nicely granules or frigid cells. They are present all over the cell except axon hillock. It resembles ribosomes and helps in synthesis of proteins. They disappear when nerve is damaged. The process is termed as Chromatolysis.
Dendrities: They are short branching processes 5 to 7 in number. They carry information towards cell.
Axon: It is the long process of neuron. It arises from the prominent portion of the cell body called axon hillock. Axon carries information away from cells the axon is covered with myelin sheath. The cells of schwann form the myelin sheath. The process of myelin sheath is myelinogenesis. The myelin sheath is interrupted at periodic interval called the nodes of ranvier.
Neurons do not multiply during life. Fortunately injury to a peripheral nerve fiber does not kill the neuron and various types of repair are possible. there are three types of nerve injuries:
1. Neuropraxia : there only pressure on the axon causing local anoxia. Recovery is possible within a few minutes to few days.
2. Axonotmesis: in this type of injury axon’s divided but the endoneurial sheath is continuous. This is due to prolonged and severe pressure on a part of neuron. Regeneration possible in this type of injury.
3. Neurotmesis: in this injury the axon and endoneurial tube are divided. Regeneration is complex. It depends on the endoneurial tube. If alignment restored regeneration is possible.