1. Learning objectives of Today’s Lecture
Describe the physiological basis of Resting membrane potential of a neuron
Enlist the sequence of events in synaptic transmission
Differentiate between Excitatory Post Synaptic Potential EPSP and Inhibitory Post Synaptic Potential IPSP

2. Synaptic transmission
Dr Ghulam Mustafa

3. Resting Membrane Potential of the Neuronal Soma.
Resting Membrane Potential -65 millivolts.
Less negative than the -90 millivolts
Lower voltage is important:
Allows both positive and negative control of the degree of excitability of the neuron.
Decreasing the voltage - less negative value - neuron more excitable
Increasing the voltage - more negative value - neuron less excitable.

4. Resting Membrane Potential of the Neuronal Soma

5. of Synaptic Transmission
The process
of Synaptic Transmission

7. 40 nm vesicles formed in GA of cell body- Motor neuron
Vesicles transported---axoplasmic streaming to nerve terminal
Acetylcholine synthesized in terminal parts of nerve - stored
Action potential opens calcium channels

8. Calcium bind with protein molecules (Release sites)
Exocytosis of Acetylcholine vesicle
2000 and 10,000 molecules of acetylcholine are present in each vesicle
Enough vesicles in the Presynaptic terminal
To transmit more than 10,000 action potentials.

9. ACETYLCHOLINE (NT) IN SYNAPTIC CLEFT
Acetyl cholinesterase Vesicles reformation
Acetate Choline Coated pits - Clathrin
Reabsorbed BACK New vesicles
ACETYLCHOLINE (NT) IN SYNAPTIC CLEFT

11. Transmitter substance activates
Ion Channel Second Msgr System

12. If transmitter substance activates an Ion Channel
opens within a fraction of
a millisecond
Cation channel Anion Channel
Sodium Ions Chloride ions
Excitatory Transmitter Inhibitory Transmitter

13. “Second Messenger” System in the Postsynaptic Neuron.
G Protein activation
Alpha Beta Gamma
Alpha

14. G Protein mediated actions
Opening specific ion channels
Activation of cAMP or cyclic cGMP in the neuronal cell.
Activation of one or more intracellular enzymes.
Activation of gene transcription.

15. If Post synaptic
Neuron
to be
Excited

16. Excitation Opening of Sodium Channels
Depressed conduction through Chloride or Potassium channels, or both.
Various changes in the internal metabolism of the postsynaptic neuron

17. Effect of Synaptic Excitation on the Postsynaptic Membrane
Increase the membrane’s permeability to Na+
Neutralizes part of the negativity of the RMP
Positive increase in voltage above the RMP
Excitatory Postsynaptic Potential (or EPSP)
20 millivolts more positive than RMP
simultaneous discharge of many terminals —about 40 to 80

18. EPSP

19. EPSP

20. If Post synaptic
Neuron
to be
Inhibited

21. Inhibition
Opening of Chloride ion channels through the postsynaptic neuronal membrane.
Increase in conductance of potassium ions out of the neuron.
Activation of receptor enzymes that
Inhibit cellular metabolic functions
Increase the number of inhibitory synaptic receptors or
Decrease the number of excitatory receptors.

22. Electrical Events During Neuronal Inhibition
Open mainly Chloride channels
Potassium efflux
Increase the degree of intracellular negativity- Hyperpolarization
Inhibitory Postsynaptic Potential (IPSP)
More negative value of -70 millivolts
IPSP of -5 millivolts

23. IPSP

24. Function of Synapses Ensure impulse to pass in one direction
Prevent damage of effectors due to over stimulation
Act as junctions for dividing up and merging of neurons

25. Let's see
Today's
Knowledge Gain

29. Resting Membrane Potential of the Neuronal Soma

30. EPSP

31. IPSP

32. Thank you