NERVE PHYSIOLOGY- NEURON & NEUROGLIA

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NEURON & NEUROGLIA

1. NERVE PHYSIOLOGY
Dr. NabeelBeeran
Dept. of Physiology
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2. Central Nervous System
The Brain + Spinal cord
The center of integration and
control
Peripheral Nervous System
The nervous system outside of
the brain and spinal cord
Consists of:
–Spinal nerves
–Cranial nerves
Responsible for communication
between the CNS and the rest of the
body.
Organization of the Nervous System
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4. Peripheral Nervous System
Somatic nervous system
Autonomic nervous system
Sympathetic divisionParasympathetic division
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5. Histology of neural tissue
Two types of neural cells in the nervous
system:
Neurons -For processing,transfer,
and storage of information
Neuroglia–For support, regulation &
protection of neurons
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6. NEURON
The functional and structural unit of the
nervous system.
Function:Send impulses to and from the CNS and
PNS and the effectors (muscles / glands).
There are different types of neurons, but most
have certain structural and functional
characteristics in common.
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8. CLASSIFICATON
OF
NEURONS
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9. DEPENDING UPON THEIR
FUNCTION
DEPENDING UPON THE NUMBER
OF POLES
DEPENDING UPON THE LENGTH
OF THE AXONS
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10. DEPENDING UPON THEIR FUNCTION
Sensory (afferent) neurons
Carry impulses from the sensory receptors
TOWARDSthe CNS
Motor (efferent) neurons
send information AWAYfrom the central
nervous system to muscles or glands.
Interneurons
send information BETWEENsensory
neurons and motor neurons.
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11. By function (connections)
Interneuron
Sensory Motor
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13. DEPENDING UPON THE NUMBER OF
POLES
i) Unipolar neurons
Have a single pole from which both the process
of axon and dendrite arise (embryonic stage in
human being)
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14. ii) Bipolar neurons
Have two poles one for axon and other for
dendrite (Vestibular, cochlear ganglia,
bipolar cells of the retina)
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15. iii) Multipolar neurons
Have many processes that extend from the
cell body. However, each neuron has only one
axon (examples: spinal motor neurons,
pyramidal neurons, Purkinje cells).
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17. DEPENDING UPON THE LENGTH
OF THE AXON
Golgi Type I neuron
-Have long axons
-The cell body of these neurons is in
central nervous system and their axons
reach the peripheral organs
Golgi Type II neuron
-Have short axons
-Present in cerebral cortex
and spinal cord
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18. STRUCTURE
OF
NEURON
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20. Cell body (Soma)
i) Nucleus-pale, large, spherical, central
ii) Neuroplasm-has neurofibrils, nissl
granules, mitochondria, golgi apparatus,
neurosecretory material
Absence of centrosome –Indicates that the
neuron has lost the ability for division
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21. Axon-
i) generally long
ii) arises from axon hillock
iii) axis cylinder has axoplasm, neurofibrils &
mitochondria
iv) axons end in terminal buttons
v) carry impulses away from cell body
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22. Axon arises from the conical extension of the cell
body –AXON HILLOCK
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23. Dendrite
i) multiple & short
ii) contain Nissl granules
iii) carry impulses towards soma
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24. Functional organization of neurons
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25. Functions of the Neuron
Cell body
1.Maintains functional and anatomical integrity of
the axon.
2.Neurotrophins ,proteins for neurotransmitters are
synthesized in the endoplasmic reticulum of the
cell body.
3.Stored in the synaptic knob by axoplasmic flow.
Dendrites
1.Receptive process of the neuron.
2.Transmits impulses towards cell body.
3.Local potentials are developed.
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26. Axon
1.Axon arises from axon hillock.
2.Long processes.
3.Forms an envelope called myelin sheath.
4.Initial segment of axon is the origin for action
potential.
5.Axon terminal form terminal knobs which store
neurotransmitters.
6.Axonal process
-Transmits propagated impulses away from cell
body to the nerve endings.
Synaptic knobs
-Neurotransmitters are stored in the nerve endings.
which get released due to the arrival of action potential.
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27. NEUROGLIA
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28. Specialized form of connective tissue cells found in
association with nervous system .
They are not excitable and they cannot conduct
impulses.
Number of neuroglia is much more than neurons .
Unlike the neurons they retain the ability to divide
and multiply throughout life.
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29. Functions
Responsible for the fixation of the neurons within
the nervous system.
Phagocytosis.
Nutrition.
Myelin sheath formation in CNS.
They acts as a “set point” for regulation of various
neural control mechanisms because of their fixed
metabolism.
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30. Types of Neuroglia
Microcytes/ Mesoglia
Astrocytes
CNS
Ependymal cells
Oligodendrocytes
Satellite cells
PNS
Schwann cells
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31. Neuroglia: Supporting Cells
Ependymal cell
Microglia
Oligodendrocyte
Astrocyte
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32. Neuroglia of CNS
•Astrocytes
–Regulate extracellular brain fluid composition
–Promote tight junctions to form blood-brain barrier
•Ependymal Cells
–Line brain ventricles and spinal cord central canal
–Help form choroid plexuses that secrete cerebrospinal fluid (CSF)
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33. Neuroglia of CNS
•Microglia
–Specialized macrophages
•Oligodendrocytes
–Form myelin sheaths if surround axon
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34. Neuroglia of PNS
•Schwann cells or neurolemmocytes
–Wrap around portion of only one axon to form myelin sheath
•Satellite cells
–Surround neuron cell bodies in ganglia, provide support and
nutrients 34

35. Microglia
•Specialized macrophages
Shows Phagocytic action.
Found in the grey matter of the CNS.
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36. Astrocytes
Found scattered throughout the CNS.
Both in grey and white matters.
Two types:
Protoplasmic Astrocytes.
Fibrous Astrocytes.
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37. Functions
Provides nutrition and remove the waste
products.
Support the neuron.
Anatomical basis of blood brain barrier.
They act as a electrical insulator.
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38. Ependymal cells
They resemble epithelial cells and line the
ventricles of the brain and central canal of
spinal cord.
Function:
Secretion of Cerebro -spinal fluid .
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39. Oligodendrocytes
Present both in grey and white matter.
Function:
To lay down myelin sheath around the nerve
fiber within the brain
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40. Satellite cells
Encapsulate the dorsal and cranial nerve
ganglion cells .
Function:
Regulate their micro environment (Barrier
formation).
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42. Schwann cells
They help in the formation of myelin sheath
around the peripheral neurons.
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43. Thank you………
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