1. Synapse and Neural Integration
بسم الله الرحمن الرحيم
Synapse and Neural Integration
Dr.Mohammed Sharique Ahmed Quadri
Assistant prof. Physiology
Al Maarefa College

2. Objectives Define synaptic transmission List the types of synapses
Describe the mechanism of action of chemical and electrical synapse.
Explain the mechanisms of excitatory and inhibitory post-synaptic potentials.
Compare EPSP &IPSP
Describe the properties of synaptic transmission

3. SNAPSES AND NEURONAL INTEGRATION
A Neuron may terminate on one of THREE structures:
1) MUSCLE
2) GLAND
3) ON ANOTHER NEURON –
JUNCTION BETWEEN TWO NEURON IS CALLED SYNAPSE

4. Synapses Junction between two presynaptic and postsynaptic neurons
There are two types of Synapse:
1. Electrical Synapses: Two neurons connected by gap junctions
2. Chemical Synapses: Chemical messenger is transmitted across the junction separating the two neurons

5. ELECTRICAL SYNAPSES
In electrical synapses, two neuron are connected by Gap Junction which allow ions (charged particles) to flow between the two cells . Therefore Action Potential travels from one cell to another.
Electrical signals are rare in Human Nervous System.

6. ELECTRICAL SYNAPSES [cont]
Example of Electrical Synapses
--- Pulp of tooth
--- Retina of the Eye
--- Cardiac Muscle
--- Smooth Muscle

7. CHEMICAL SYNAPSES
In human CNS , most of the synapses are Chemical, where chemical messenger transmits information from one neuron to another .
WE WILL DISCUSS CHEMICAL SYNAPSE

8. synapse

9. Synapse

10. Synaptic Delay
Transmission of electrical impulse [AP] by chemical means from presynaptic neuron to post-synaptic neuron takes time. It is called ‘Synaptic Delay’. It is 0.5 to 1 millisecond.

11. Synapses
Signal at synapse either excites or inhibits the postsynaptic neuron
Two types of synapses
Excitatory synapses
Inhibitory synapses

12. Neurotransmitters Vary from synapse to synapse
Same neurotransmitter is always released at a particular synapse
Quickly removed from the synaptic cleft
Some common neurotransmitters
Acetylcholine
Dopamine
Norepinephrine
Epinephrine
Serotonin
Histamine
Glycine
Glutamate
Aspartate
Gamma-aminobutyric acid (GABA

13. ‘Important’
Glutamate – Most common excitatory neurotransmitter in the brain. It causes EPSP.
GABA [Gamma amino butyric acid] – Most common inhibitory neurotransmitter in brain. It causes IPSP.

14. Neurotransmitter Removal From The Synaptic Cleft
Neurotransmitters are quickly removed from the synaptic cleft by various ways:
Inactivated by enzymes present on post synaptic membrane.
Diffuse away from synaptic cleft.
Actively taken back into axon terminal.

15. Neuropeptides Large molecules consisting of from 2 to 40 amino acids
Synthesized in neuronal cell body in the endoplasmic reticulum and Golgi complex
Packaged in large, dense-core vesicles present in axon terminal
Neuropeptides are considered neuromodulators don’t cause the formation of EPSP or IPSP, but bring about long term changes that subtly modulate, depress or enhance the action of the synapse

16. Comparison of Classical Neurotransmitters and Neuropeptides

17. Post-Synaptic Potential
EPSPs and IPSPs are graded potential [local]. They can be summated [added].
Types of Summation
1. Temporal Summation
2. Spatial Summation

18. Temporal Summation
When single presynaptic neuron is stimulated many times after short intervals, to summate several EPSP, it is called ‘Temporal Summation’.
Up to 50 EPSPs might be needed to bring post-synaptic membrane to threshold level.

19. Spatial Summation
When two or more excitatory neurons are stimulated together at the same time, to get the action potential.
It is called Spatial Summation.

21. Presynaptic inhibition or facilitation can selectively alter the effectiveness of a presynaptic input.

22. Convergence And Divergence
On a given neuron, many other neurons come and synapse on it. It is called ‘Convergence’.
Due to convergence input, a single neuron is influenced by thousands of other cells.

23. Convergence And Divergence [cont]
It refers to the branching of axon terminals so that single cell synapses with many other cells.

24. Convergence And Divergence

25. ‘Important Information’
There are about 100 billion neurons in the brain.
A single neuron maybe connected to 5000 to 10,000 other neurons.
Brain is responsible for different activities like sensations, movements of muscle, thought, emotion, memory – all these depend on electrical and chemical signaling between neurons along wired neural pathways.

26. Synaptic Drug Interactions
Possible drug actions
1. Altering the synthesis, axonal transport, storage, or release of a neurotransmitter
2. Modifying neurotransmitter interaction with the postsynaptic receptor
3. Influencing neurotransmitter reuptake or destruction
4. Replacing a deficient neurotransmitter with a substitute transmitter

27. Assignment
Drugs and diseases that modifies the synaptic transmission

28. References Human physiology by Lauralee Sherwood, seventh edition
Text book physiology by Guyton &Hall,11th edition
Text book of physiology by Linda .s contanzo,third edition