CNS

1. Dr. Hany Gamal
Physiology of
The Central Nervous System

2. Central nervous system
Brain
Spinal cord
Peripheral nervous system
Cranial nerves
Spinal nerves
Higher brain level
Lower brain level
Spinal cord level
Afferent (sensory)
Efferent (motor)
- somatic
- autonomic

3. Types of Cells in the Nervous System
1- Neurons. (about 50% of all cells) 2- Glial Cells: (50% of all cells)
- microglial cells.
- Oligodendrocytes.
- Astrocytes.
- Ependymal cells.

4. Synaptic Transmission

5. Synapse

7. Axosomatic
Axodendritic
Axoaxonic Postsynaptic
neuron

8. Types of synaptic transmission
Electric transmission Chemical transmission

9. Chemical transmission
- Small clear.
- Small granular.
- Large granular.
30-50 nm

10. Mechanism of synaptic transmission
1- Release of chemical transmitter.
2- Binding of chemical transmitter with its receptor.
3- Generation of postsynaptic potential.
4- Removal of chemical transmitter.

11. (V-snare protein)
(T-snare protein)
Mechanism of release of synaptic transmitter

12. Ca++

14. Generation of postsynaptic potential
Binding of chemical transmitter to its receptor causes
opening or closure of membrane ion channels
change in membrane conductance to ions
flow of ions
change in postsynaptic membrane potential

15. Removal of chemical transmitter
microglia

16. Excitatory postsynaptic potential (EPSP):
EPSP
Opening of Na+ (or Ca++)
Ligand-gated channels

19. Inhibitory postsynaptic potential (IPSP):
threshold
stimulus
Membrane
potential
mV
IPSP

20. Grand Postsynaptic potential (GPSP):
Na+ voltage-gated channels

21. Presynaptic Potentials
Control the release of chemical transmitters
from presynaptic terminal.

22. serotonin
C-AMP
kinase
K+ channel
Ca++
channel
Postsynaptic
neuron
Presynaptic fiber
Presynaptic Facilitation

23. Presynaptic Inhibition

24. Characters of synaptic transmission:
1- one way transmission.
2- delay 0.5 msec.

25. Number of synapses in a reflex = Central delay
0.5

26. Characters of synaptic transmission:
1- one way transmission.
2- delay 0.5 msec.
3- Fatigue.
4- Synaptic plasticity.

27. Synaptic Plasticity
Ability of the synapse to change its strength
Short term plasticity
Develops rapidly and
lasts for short time
Long term plasticity
Develops slowly and
lasts for longer time

28. Short Term Plasticity
1- Short term Inhibition. Habituation
Inactivation of Ca++ channels

29. Short Term Plasticity
2- Short term facilitation.
- Post-tetanic potentiation
Ca++ Ca++
Ca++ pump
- Sensitization
Presynaptic facilitation

30. Glutamate
AMPA
NMDA
Na
Na
Ca++
Ca++
Calmodulin
+ Kinase II
NO
NO
Mg++
Na
Na
Ca++
Long-Term Plasticity
Long term potentiation

31. Long term inhibition
Long-Term Plasticity
?? Decrease release of chemical transmitter
?? Decreased number of postsynaptic receptors.

32. Factors affecting synaptic transmission:
1- Changes in internal environment:
- pH: acidosis - - inhibits alkalosis + + enhances
- Hypoglycemia: - - inhibits
- Hypoxia: - - inhibits
2- Drugs:
- Caffeine: depolarize postsynaptic membrane.
- Strychnine: competes with inhibitory transmitters.
- Analgesics, hypnotics and anesthetics.
3- Diseases:
- Tetanus: inhibits the release of GABA (spastic paralysis)
- Botulism: inhibits release of Ach. (flaccid paralysis)
- Myasthenia gravis: