Structure, function and classification of neuron

1. Structure, Function And Classification
By: Dr.Sara Sadiq
Neuron

2. • Two Anatomical Divisions
– Central nervous system (CNS)
• Brain
• Spinal cord
– Peripheral nervous system (PNS)
• All the neural tissue outside CNS
• Afferent division (sensory input)
• Efferent division (motor output)
– Somatic nervous system
– Autonomic nervous system
General Organization of the nervous system

3. General Organization of the nervous system
Brain & spinal cord

4. Two types of neural cells in the nervous system:
 Neurons - For processing, transfer, and storage of
information
 Neuroglia – For support, regulation & protection of
neurons

5. Neuron :
The basic unit of nervous
system
CNS contain more then
100 billion neurons

7. Nerve Cell Body
• Also known as Soma or Perikaryon
• Contain:
Cell membrane => Neurilemma
Cytoplasm => Neuroplasm
Large nucleus => no centrosome
Endoplasmic raticulum => Nissl bodies
Mitochondria
Golgi appratus
Neurofibrils

9. •Myelin is wrapped
around the axon of
many neurons
•In periphery, myelin
is produced by
Schwann cells
•In CNS, it is
produced by
oligodendrocytes

10. • The presence of myelin
speeds up the transmission of
action potentials along the
axon
• The impulse jump from one
node to another node =>
Saltatory Conduction
• Myelin sheath has high
insulating capacity so
prevents the stimulation of
neighboring nerve fibers
• Unmyelinated gaps known as
“nodes of Ranvier”

11. • Regions of the nervous system containing
groupings of myelinated axons make up the
“white matter”
• “gray matter” is mainly comprised of groups of
neuron cell bodies, dendrites & synapses

12. Classification of Neurons
• Anatomical classification
1) Depending upon the number of poles
2) Depending upon the length of axon
• Functional classification => Depending upon
the function

13. Figure 12.4
1. Classification of Neurons Depending
Upon No: Of Poles

14. Anaxonic neurons
• no anatomical clues to
determine axons from
dendrites
• functions unknown

15. Unipolar neuron:
• Single process coming
off cell body, giving rise
to dendrites (at one
end) & axon (making up
rest of process)
• Present only in
embryonic life

16. Pseudounipolar neuron:
• Single short process that
branch like a T to form a pair
of longer processes
• Ex: Sensory neurons

17. Bipolar neuron
• two processes coming
off cell body – one
dendrite & one axon
•Dendrite is speciallized
to recive specific stimulus
•Axon conduct action
potential to CNS
•Ex: Retina of eye
Nasal cavity

18. Multipolar neuron
• multiple dendrites &
single axon
• most common type
of neuron within CNS

20. 2. Classification of Neurons Depending
Upon The Length Of Axons
1) Golgi Type-I Neuron:
• Long axons
• Cell bodies nare located in different parts of CNS and
their axons reach the peripheral organs
2) Golgi Type-II Neuron:
• Short axons
• Present in cerebral cortex and spinal cord

21. Functional classification
• Sensory (afferent) neurons
• Motor (efferent) neurons
• Interneurons

22. Sensory (afferent) neurons
•Transmit sensory
information from
receptors of PNS
towards the CNS
• Most sensory
neurons are unipolar, a
few are bipolar

23. Motor (efferent) neurons
• Transmit motor
information from the CNS
to effectors
(muscles/glands/adipose
tissue) in the periphery of
the body
• All are multipolar

24. Interneurons
• Transmit information between neurons
within the CNS; analyze inputs, coordinate
outputs
• Are all multipolar

26. Thank You