Synaptic Transmission.pptx

Synaptic Transmission

1. SYNAPTIC TRANSMISSION Dr. Geetanjali Purohit Professor Department of Physiology Dr. M K Shah MCRC

2. PY 10.2 Describe and discuss the functions and properties of synapse, reflex, receptor

3. SLO’s 1. Describe the main morphologic features of synapses. 2. Distinguish between chemical and electrical transmission at synapses 3. Define convergence and divergence in neural networks, and discuss their implications. 4. Describe fast and slow excitatory and inhibitory

4. S Y N A P S E The junction where the axon of one neuron ( Presynaptic neuron) terminates on the dendrites, soma or axon of another neuron (Postsynaptic neuron) Types of Synapses Chemical Electrical and Conjoint Through Neurotransmitters Almost all synapses in human C.N.S. Around 40 transmitters Through Gap junctions Only a few In smooth & cardiac muscles.

5. Physiological classification of Synapse Chemical synapse Electrical synapse Chemical mediators are released from pre to post synaptic site Pre and post membranes are close to each other by a low resistance bridge–Gap Junction through which ions pass Seen in most of the synaptic junctions Found at few locations like in lateral vestibular nuclei, hippocampus and cerebral cortex Allows large number of synapses per neurons and a large variety of neurotransmitters. Helpful in the processing of learning and memory. Too many synapses on the same neuron thus transmission is rapid and efficient. Sensitive to hypoxia Insensitive hypoxia Synaptic cleft is present Cleft is replaced by low resistance bridge Synaptic delay is observed No synaptic delay

6. Functional Anatomy and Transmission

7. Kiss and Run discharge

8. ***Tetanus and botulinum toxins are acting on synaptobravin and syntaxin and prevent the NT discharge Note: botulinum toxins is used for achlasia cardia and the treatment of wrinkles

9. Electrical Events at Synapse: Excitatory Postsynaptic Potentials (EPSP) >Single stimulus of one synaptic knob > After a synaptic delay of 0.5 ms >Opening of voltage-gated Na+ channels > A local and graded depolarizing potential produced in PS membrane > excitability to other stimuli is increased.

10. Electrical Events at Synapse: (contd.) Inhibitory Postsynaptic Potentials: (IPSP ) >Single stimulation of some pre synaptic fibers > Opening of Cl ˉ channels > Influx of Cl ˉ > Local hyperpolarizing potential > Decreased excitability to other stimuli.

11. EPSP & IPSP

12. Summation ****When the algebraic sum of EPSP and IPSP reach 10–15 mV (firing level), Action Potential results at the Axon Hillock. 1. Spatial summation: Activities in many synaptic knobs at the same time. 2.Temporal summation: Repeated afferents in a single knob causing new EPSP before the decay of previous EPSP.

13. 1. Electrical synapse conducts impulse from one cell to another freely due to the presence of which of the following component? A.Neurotransmitter B.Chemicals C.Gap junction D.Tight junction 2. Which of the following causes rupture of synaptic vesical at the presynaptic end of synapse? A.Ca2+ influx B.Na+influx C.K+influx D.Ca2+efflux 3. Repeated afferents in a single knob causing new EPSP before the decay of previous EPSP k/as . a. Temporal summation b. spatial summation c. Quantal summation d. none 4. Excitatory post synaptic potential EPSP occurs due to entry of which of the following ion into the post-synaptic neuron? A. Na+ ion B.Ca2+ ion C. K+ ion D. H+ ion 4. Inhibitory post synaptic potential IPSP occurs due to entry of which of the following ion into the post-synaptic neuron? A. Na+ ion B. Ca2+ ion C. Cl - ion D. H+ ion