This document describes the key parts and functions of a neuron. It discusses the soma, dendrites, axon and myelin sheath. The soma contains organelles and extends into dendrites and an axon. Dendrites receive signals and transmit them to the soma. The long axon transmits output signals away from the soma. The myelin sheath acts as an insulator around many axons. Nodes of Ranvier allow faster signal conduction along myelinated axons. The document also briefly discusses neurotrophic factors that support neuron growth and survival.

3.  Cell body (soma)
 Axon
 Dendrites

4. Axon of another
neuron
Cell BodyDendrites
Axon
Myelin
Sheath
Dendrites of
another neuron

6.  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

7.  Soma extend into dendrites on one end and
axon on the other
 Membrane called plasmalemma

8.  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

10.  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

12.  It’s a protective insulator covering of the axon
 Formed by schwann cells
 Double layer membrane of a single schwann
cell 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

16.  Nodes of Ranvier
 Internodal distance is 1-2mm and each node is
0.5-1 micrometer

17.  Increases speed of conduction
 It reduces energy expenditure by the cell
 Provides protective covering of the axon

18.  Myleniated Axons
 Unmyelinated Axons

19.  Different neurons in body shows diff time of
myelination
 Starts early as 4th month of fetal life and
completes by 2 years

20.  Transfer of substances between cell body and
axon terminal
 For the development of neuron
 Bi-directional transport

21.  Anterograde transport
 Retrograde transport
 Transneuronal transport

22.  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

23.  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

24.  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

25.  Based on function
 Myelination
 Erlanger and gasser classification

27.  Demyelinating diseases
1) multiple sclerosis
2) Gullian barre syndrome

28.  Wallerian degeneration

29.  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

31.  Neurotrophins
 Other growth factors ( FGF,IGF-1, PDGF ,
CNTF,GDNF)

32.  Nerve growth factor
 Brain derived neurotrophic factor
 Neurotrophin-3
 Neurotrophin 4/5