Soma or prikariyon
Nucleus and cytoplamic organelles
Nissels granules = RER
Cytoskeletal proteins like neurofilaments,microtubules , actin microfilaments
Nucleus contain one or two nucleolus ,and no centriole
Terminally differentiated cells
Numerous short extensions from cell body
Increasing surface area
Dendritic spines
Receive incoming signals and transmits them
Helps in protein synthesis
Helps in generating ACTION POTENTIAL
Axon fibers form the nerve
Long cylindrical process extends away from cell body
Transmits output signals (Action Potential )
Contains organelles , cytoskeleton, axoplasm
Axon hillock - initial segment portion of neuron
Axon terminal – axon divides into several processes and has synaptic knobs
Buttons contains neurotransmitters
It’s a protective insulator covering of the axon
Formed by schwann cells
Double layer membrane of a single schwanncell wraps itself several times around axon
1 mm in length , 8 -10 micrometer in thickness
Layers stick to each other due to protein p0
Schwann cell nucleus lies in the outermost layer
Increases speed of conduction
It reduces energy expenditure by the cell
Provides protective covering of the axon
Different neurons in body shows diff time of myelination
Starts early as 4th month of fetal life and completes by 2 years
Transfer of substances between cell body and axon terminal
For the development of neuron
Bi-directional transport
From ell body to axon terminal
Mainly for neurotransmitters
Two types – fast and slow
Fast – 400mm/day by kinesin
Slow- 0.5 – 2 mm/day
Slow transport helps in nerve repair
From axon terminal to cell body
200mm /day done by dynin
Keeps soma informed about synaptic environment
Transports viruses such as varicella Zoster , rabies
Transport toxins
Transports nerve growth factor
Voltage gated Na channels are mainly concentrated on nodes of ranvier
Voltage gated Ca channels are mainly present at the axon terminal for neurotransmitter secretion
5 grades
1st-transient loss of function
2nd- severe injury due to prolonged pressure, intact endoneurium complete recovery but delayed
3rd- severe damage to endoneurial sheath
4th- disruption of nerve fasciculi
5th- complete transection