Physiology of Synapse I Synapse types I Functional elements of synapse I Nervous System Physiology This video will be about 1. Definition of synapse 2. Classification of synapse - anatomical, functional classification 3. Functional elements of synapse 4. Presynaptic axon terminal 5. Types of synaptic vesicles 6. Active zone 7. Components of active zone 8. Functions of active zone 9. Synaptic cleft 10. Postsynaptic membrane You can also watch the same topic on HM Learnings Youtube channel. You can also follow HM Learnings on facebook, instagram and twitter for daily updates

2. Synapse
• Junction where the presynaptic cell (neuron) terminates on the
postsynaptic cell (another neuron/ muscle/ gland).
• Formation of new synapses and synaptic modifications continue
throughout the life of an individual.

3. Types of Synapse
• According to the part of the neuron involved in synapse formation
1. axodendritic synapse e.g. cerebral and cerebellar cortex
2. axosomatic synapse e.g. basket cell of cerebellum
3. axoaxonal synapse e.g. presynaptic inhibition
4. dendrodendritic synapse e.g. granule cell (no axon) of olfactory bulb
form synapse with mitral cell, retina

5. • According to the nature of transmission
1. Chemical transmission – release of neurotransmitters
2. Electrical transmission – gap junctions (retina, olfactory bulb,
hippocampus)
3. Conjoint transmission – partly electrical, partly chemical
• According to the number of neurons involved
1. One to one e.g. neuromuscular junction
2. One to many e.g. sympathetic system
3. Many to one e.g. CNS

7. Functional elements of synapse
1. Presynaptic axon terminal and presynaptic membrane
2. Synaptic cleft
3. Postsynaptic membrane

8. Presynaptic axon terminal
• Mitochondria
• Synaptic vesicle – membrane enclosed
vesicles containing neurotransmitter
• Active zone

9. Types of Synaptic vesicle
1. Small vesicle with clear core- Acetylcholine, GABA, glutamate,
glycine
2. Small vesicle with dense core- norepinephrine, epinephrine,
dopamine (catecholamines)
3. Large vesicle with dense core- neuropeptides (substance P,
enkephalin, neuropeptide Y )

10. Active zone
• Active zone is a dense region of presynaptic terminal where synaptic
vesicles are concentrated, tethered to presynaptic membrane, some are
docked and primed and are in fusion ready state.

11. What does active zone consists of ?
• Cytoskeleton proteins that attach synaptic vesicle to the presynaptic
membrane (actin, myosin, tubulin, spectrin)
• Neural adhesion molecules like neurexin bind to its postsynaptic
component (neuroligin) for maintaining the matrix of synapse.
• Proteins involved in docking, priming and fusion of vesicle (SNARE
complex).
• Proteins involved in synaptic vesicle endocytosis (clathrin, dynamin).
• Contains voltage gated calcium channel.

12. Functions of active zone
• It ensures the orderly organization of synapse so that the
neurotransmitter release from presynaptic neurons occur in close
proximity to the postsynaptic density.
• It maintains the architecture of synapse.
• It ensures the release of neurotransmitter on arrival of action
potential.

13. Synaptic cleft
• It is the gap between the presynaptic and postsynaptic membrane.
• It is about 20-40 nm in width.

14. Postsynaptic membrane
• Postsynaptic receptors are clustered in a thickening on the
postsynaptic membrane called as the postsynaptic density.
• Binding proteins (neuroligin) and enzymes are also present in
postsynaptic density.

15. Upcoming Video
• Process of neurotransmission
• Properties of synapse