1. Synaptic Transmission

2. Synapses
The “synapse” is the physical gap between pre- and post-synaptic membranes (~20-30 nMeters)
Presynaptic membrane is typically an axon
The axon terminal contains
Mitochondria that provide energy for axon functions
Vesicles (round objects) that contain neurotransmitter
Cisternae that are a part of the Golgi apparatus: recycle vesicles
Postsynaptic membrane can be
A dendrite (axodendritic synapse)
A cell body (axosomatic synapse)
Another axon (axoaxonic synapse)
Postsynaptic thickening lies under the axon terminal and contains receptors for transmitters

3. Synapses
Junction is the connection between a nerve cell and another (muscle fiber or gland).
Synapse is the connection between 2 nerve cells.

4. Synapses

5. CLASSIFICATION OF SYNAPSES

6. Synapses could be classified according to
1- Either their location between the pre and postsynaptic neurons (histological classification)
2- The mechanism of transmission of impulses across them (physiological classification)

7. histological classification
synapses are classified into three types:-
1. Axodendritic synapses: These are synapses between the axon terminals of the presynaptic neuron and the dendrites of the postsynaptic neuron.
2. Axosomatic synapses: These are synapses between the axon terminals of the presynaptic neuron and the soma of the postsynaptic neuron
3. Axoaxonic synapses: These are synapses between the axon terminals of the presynaptic neuron and the axon of the postsynaptic neuron.

8. histological classification

9. PHYSIOLOGICAL CLASSIFICATION
synapses are classified into three types:
1. CHEMICAL SYNAPSES:
2. ELECTRICAL SYNAPSES:
3. CONJOINT SYNAPSES: (ELECTROCHEMICAL)

10. CHEMICAL SYNAPSES
In these synapses, transmission of signals occurs by releasing a ''chemical transmitter" from the presynaptic terminal into the synaptic cleft.
The transmitter then acts on specific receptors on the postsynaptic membrane to generate postsynaptic potential.
There are more than 40 different synaptic transmitters in the CNS which are either small molecule rapidly acting (acetylcholine) or large molecule slowly acting (substance P).
Chemical synapses are the only type of synapses found in the human nervous system.

11. ELECTRICAL SYNAPSES
In these synapses, there are gap junctions between the pre and postsynaptic membranes which allow the transmission of the depolarization wave directly from the pre to the postsynaptic membrane.

12. CONJOINT SYNAPSES
In these synapses, transmission of impulses occurs by both mechanisms electrical and chemical.
They are found in some fish and invertebrates.

13. SYNAPSES Action potential
 synaptic knob
 opening of Ca+ channels
neurotransmitter vesicles fuse with membrane
release of neurotransmitter into synaptic cleft
binding of neurotransmitter to protein receptor molecules on receiving neuron membrane
opening of ion channels
triggering of new action potential
Neurotransmitter is broken down by enzymes & ion channels close.

14. SYNAPTIC

15. Cell-to-Cell Communication Between Neurons Takes Place At Synapses
A synapse is a region at which a neuron communicates with its target cell. The synapse is composed of 3 parts: (a) the axon terminal; (b) the synaptic cleft, the space between the cells and (c) the membrane of the postsynaptic cell.

16. Acetylcholine (ACh): Synthesis and Breakdown
Synthesis requires the enzyme choline acetyltransferase (ChAT)
Made from choline (Ch) and acetyl coenzyme (acetyl CoA) in the axon terminal then filled into synaptic vesicles.
Once released into the cleft, its rapidly broken down by the enzyme acetylcholinesterase (AChE).
Ch is transported back into the axon terminal and reused to make ACh.