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Physiology of Synapse and Applied
- 1. Physiology of Synapse And Applied Dr. Anupam Mittal MBBD, MD King George’s Medical University, Lucknow
- 2. Contents 1. Introduction 2. Structure 3. Synapse 1. Types 2. Neuronal synapse type 3. Type according to transmission 4. Synaptic Transmission 1. Electrical 2. Chemical 1. Transmission of Neurotransmitters 5. Applied
- 3. Consists of : • The soma ( cell body ) • Dendrites • Axons Neuron : Cellular Level
- 4. Human brain is made up of 80 - 100 billion neurons They “talk” to each other using signals
- 7. The junction between two neurons is called a Synapse
- 8. Synapse
- 9. Types
- 11. Types on the basis of Synaptic Transmission 1.Electrical 2.Chemical
- 12. 1. Electrical Transmission • Present in regions of most brain • Including the inferior olive, cerebellum, spinal cord, neocortex, thalamus, hippocampus, olfactory bulb, retina, and striatum.
- 13. 1. Electrical Transmission : Structure • Plasma membrane of coupled cells become closely apposed (~3nm) • Each gap junction channel formed by Two hemichannels called Connexons • Each connexon is hexamer of connexin protein subunit • Allows current to flow directly from one cell to another
- 14. Structure
- 16. Gap junction structure Freeze-fracture electron microscopy
- 17. 2. Chemical Transmission • No communication between cytoplasm of two cells • Synaptic Cleft ~20nm • Impulse transmission, is carried by Neurotransmitter • Either excite the neuron, inhibit it, or modify its sensitivity • Example of Neurotransmitter : • Acetylcholine, norepinephrine, epinephrine and other • “One- Way” Conduction
- 18. 2. Chemical Transmission : Steps 1. Neurotransmitter 2. Vesicle 3. Exocytosis 4. Synaptic Cleft 5. Post Synaptic membrane - Receptors 6. Endocytosis
- 23. Clinical Applied
- 24. • Myasthenia Gravis • Lambert- Eaton Syndrome • Botulism toxoid
- 25. Myasthenia Gravis • Autoimmune disorder • Autoantibodies - block or destroy the acetylcholine receptors at the NMJ • Neurotransmitter can not produce enough Action Potential • Worst after activity, Better at rest
- 28. Lambert- Eaton Syndrome • Auto-immune condition • Associated with Small Cell Carcinoma of Lung • Dysfunction at Neuro muscular junction • Antibodies against the calcium channels on Presynaptic neuron
- 31. Botulism / Tetanus Toxoid • In Both diseases causative agent is a toxin produced by a bacteria • Enter via Na Choline Co transporter (Pre-Synaptic) • Cleaves the SNARE protein • Prevent the release of neurotransmitter into synapse • By inhabiting vesicular fusion
Editor's Notes
- Cell Body Contain the nucleus the site of metabolic activity. Most of the neurotransmitters that will eventually be released at the synapse are synthesized here Dendrites Small projections from the cell body that serves a receptive role in the physiology of the neuron. They receive incoming signals from other neurons and relay them to the cell body, where the signals are integrated, and a response will be initiated. Axons The outflow tract of the neuron. It is a cylindrical tube that is covered by the axolemma and is supported by neurofilaments and microtubules. The microtubules will help to transport the neurotransmitters from the cell body down to the pre-synaptic terminal, where they will be released.
- Axo Dendritic - Excitatory Axo somatic - Inhibitory Purkinje cell Cerebellum Axo axonic Visual cortex Striatum (Basal Ganglia) Solitary Nucleus Baroreceptor – Plays role in baroreflex Spinal Cord Dendro dendritic Spinal cord (Gabaergic neuron) Olfactory pathway (Glomerulus Body)
- Small black arrows - Two dendritic spines are coupled by a gap junction. Large arrowheads point to the electron-dense material that marks the active zones. Black dots are immunogold labeling for GABA, thus identifying this terminal as GABAergic. Red arrowheads point to synaptic vesicles.
- Action Potential —> Voltage gated calcium channels open —> Influx of Ca Ion —> Cause synaptic vesicles to fuse with the cell membrane, releasing their contents by exocytosis The neurotransmitter diffuse across the synaptic cleft The neurotransmitter binds to the neuro receptors in post synaptic membrane, causing the channels to open
- The synapse consists of A presynaptic ending that contains neurotransmitters, mitochondria and other cell organelles. A postsynaptic ending that contains receptor sites for neurotransmitters. A synaptic cleft or space between the presynaptic and postsynaptic endings. It i s about 20nm wide.
- Cause — Thymoma – thymus produce antibody Ptosis – Levator Palpebrae muslce Diplopia – Extraocular Muscle Diminished facial expression Respiratory Depression Weakness Tensilon test – IV Endrophonium Treatment – Thymectomy, Medicine
- Botulism : By Clostridium botulinum, no release of ACH, produce inhibitory effects, prevents muscle contraction, caused flaccid paralysis Tetanus: By Clostridium Tetani, prevents release of GABA and glycine, both are inhibitory, Specifically their release is inhibited in Renshaw cells in spinal cord, produces symptoms like UMN, Spastic paralysis, lock jaw and opisthotonos.