Structure of Axon
1. Axolemma
The plasma membrane of Axon is called axolemma and it enclose cytoplasmic extension (cytoplasm of Axon), (Axoplasm), surrounded by its plasma membrane.
Myelin sheath and Neurilemma
Some axon covered with layer of whitish lipid sheath called myelin sheath.
The outer layer or sheath is neurilemma or Schwann sheath.
Between the layer of plasma membrane there are small amount of fatty substance called myelin.
Myelinated nerve fibers transmits nerve impulse faster than unmylinated sheath.
Myelin sheath protecting nerve and insulating layer; transmission of electrical impulse.
Nodes of Ranvier
Myelin sheath is segmented, interrupted at regular intervals by gaps called nodes of ranvier. NOR assist rapid transmission of nerve impulse in myelinated neurons.
Schwann Cells
Schwann cells are cells in peripheral nervous system that form the myelin sheath around neurons axon.
Unmyelinated sheath
A nerve fiber that doesnot have myelin sheath is unmyelinated fibres.
These fiber conduct impulses slow speed.
Small neurons which are present in CNS are non-myelinated.
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