Cell body (soma)

Axon

Dendrites

Axon of anotherneuron

Cell BodyDendrites

Axon

MyelinSheath

Dendrites of another neuron

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

Soma extend into dendrites on one end and axon on the other

Membrane called plasmalemma

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

Nodes of Ranvier

Internodal distance is 1-2mm and each node is 0.5-1 micrometer

Increases speed of conduction

It reduces energy expenditure by the cell

Provides protective covering of the axon

Myleniated Axons

Unmyelinated Axons

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

Anterograde transport

Retrograde transport

Transneuronal 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

Based on function

Myelination

Erlanger and gasser classification

Demyelinating diseases

1) multiple sclerosis

2) Gullian barre syndrome

Wallerian degeneration

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

Neurotrophins

Other growth factors ( FGF,IGF-1, PDGF , CNTF,GDNF)

Nerve growth factor

Brain derived neurotrophic factor

Neurotrophin-3

Neurotrophin 4/5