BIO203_Synapse

BIO203_Synapse - Synaptic Transmission Electrical Synapses...

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1 Synaptic Transmission • Electrical synapses • Rapid cell-to-cell transfer of electrical activity from one cell to another cell • Gap junction-mediated electrical current flow • Chemical synapses • Slower cell-to-cell transfer • Signal transfer across synaptic cleft via secretion of diffusible chemical messenger(s) Electrical Synapses Sherwood, Klandorf & Yancey, Animal Physiology: From Genes to Organisms , Figures 2-34, 9-20 • Passive (electrotonic) current flow from pre- synaptic (signal-sending) cell to post-synaptic (signal- receiving) cell • High degree of gap junctional coupling produces a functional syncytium for coordinated activity of the population of “electrically coupled” cells • Non-directional: capable of passing current in both directions under experimental conditions CARDIAC MUSCLE Chemical Synapses Pre-synaptic and post-synaptic cells separated by a synaptic cleft • action potential enters axon terminal of pre-synaptic cell • depolarization of synaptic knob causes opening of voltage-gated Ca 2+ channels •Ca 2+ enters synaptic knob •Ca 2+ -stimulated exocytosis of synaptic vesicles containing chemical neurotransmitter • neurotransmitter diffusion across synaptic cleft (adds delay) • neurotransmitter reception by ligand-gated ion channels in post- synaptic cell membrane • depolarization or hyperpolarization of post-synaptic cell membrane according to nature of neurotransmitter and ion channel The effect on the post-synaptic cell is: • excitatory if the post-synaptic cell membrane is driven toward the threshold for action potential initiation • inhibitory if the post-synaptic cell membrane is driven or held at
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This note was uploaded on 09/16/2011 for the course BIO 203 taught by Professor Loretz during the Fall '09 term at SUNY Buffalo.

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BIO203_Synapse - Synaptic Transmission Electrical Synapses...

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