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Excitable Tissues- Synapse

Excitable Tissues- Synapse

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Excitable Tissues- Synapse

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  1. Excitable Tissues- Synapse Prof. K. Sivapalan

  2. Synapses • Two or more neurons communicate through synapse. • Communications are formed with the cell body, dendrides or with the axon sometimes. Synapse

  3. Structure of a synapse • Pre-synaptic and post synaptic membrane • Synaptic cleft- 20-40 nm. • Synaptic vesicles- transmitter • Transmitters released by exocytosis and recovered by endocytosis or destroyed by enzymes Synapse

  4. Sequence of Events at the Axon Terminal • Action potential arrives in the axon • Voltage gated calcium channels at the pre-synaptic membrane open and calcium ions enter • Calcium activates release of synaptic vesicles • Synaptic vesicles cross the cleft and bind with the receptors in the post synaptic membrane. Synapse

  5. Events at the Post Synaptic Membrane • The transmitters released in the cleft bind with receptors in the post synaptic membrane • The transmitter may increase the conductivity (permeability) of cl- or Na+ [sometimes Ca++] • Ligand gated channels • This leads to entry of the respective ion into the ICF resulting in change in membrane potential. • Entry of cation alters the potential towards threshold level [EPSP] and anion causes hyper polarization [IPSP] • EPSP and IPSP from multiple synapses [spacial] or repeated [temporal] release from the same synapse are summated. Synapse

  6. Genesis of action potential in Post Synaptic Neuron Synapse