A neuron is the structural and functional unit of the nervous tissue. A neuron is made up of cyton or cell body and cytoplasmic extensions or processes.
1. Cyton:
The cyton or cell body contains granular cytoplasm called neuroplasm and a centrally placed nucleus. The neuroplasm contains mitochondria, Golgi apparatus, RER and Nissl’s granules.
2. Cytoplasmic extensions or processes:
(a) Dendron: They are short, unbranched processes.
The fine branches of a dendron are called dendrites.
Dendrites carry an impulse towards the cyton.
(b) Axon: It is a single, elongated and cylindrical process.
- The axon is bound by the axolemma.
- The protoplasm or axoplasm contains large number of mitochondria and neurofibrils.
- The axon is enclosed in a fatty sheath called the myelin sheath and the outer covering of the myelin sheath is the neurilemma. Both the myelin sheath and the neurilemma are parts of the Schwann cell.
- The myelin sheath is absent at intervals along the axon at the Node of Ranvier.
- The fine branching structure at the end of the axon (terminal arborization) is called telodendron.