PDBIO 305: The Synapse - Week 4
PDBIO 305: The Synapse - Week 4 PDBIO305
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This 2 page Class Notes was uploaded by Kirsten Notetaker on Friday October 14, 2016. The Class Notes belongs to PDBIO305 at Brigham Young University taught by David Thomson in Fall 2016. Since its upload, it has received 8 views. For similar materials see Human Physiology in Physiology and Developmental Biology at Brigham Young University.
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Date Created: 10/14/16
The Synapse Summary of nerve transmission so far: 1) Graded potentials occur on the cell membrane of the nerve 2) If they are big enough, or if enough occur simultaneously, the membrane is depolarized to threshold, setting off an action potential which spreads down the nerve axon Synapse = connection between two neurons Sequence of events in a synapse (helpful to draw it out for yourself) 1. Action potential depolarizes presynaptic membrane 2. Voltage-gated Ca ++channels open, Ca ++enters presynaptic axon ter++nal 3. Ca triggers exocytosis of neurotransmitter 4. Neurotransmitter binds to receptor on postsynaptic cell membrane 5. Postsynaptic neuron responds 6. Neurotransmitter may be degraded by enzymes OR taken back up by presynaptic neuron OR diffuse away from synapse Chemically gated ion channels EPSP: Excitatory Post-Synaptic Potential Neurotransmitters cause depolarization of the postsynaptic neuron With channels that allow both K and Na through, electrochemical gradient favors movement of Na inside the cell + and inhibits K movements outside of the cell because the cell at rest is negatively charged IPSP: Inhibitory Post-Synaptic Potential + Channels open which only let K through, which moves out of the cell and hyperpolarizes the postsynaptic neuron There are other ways for IPSP to occur, but we won’t cover them in this class Whether an EPSP or IPSP occurs depends on the type of neurotransmitters Summation Temporal summation: adding together of EPSPs or IPSPs generated by firing of the same presynaptic terminal at high frequency Spatial summation: adding together of EPSPs or IPSPs generated by firing of two or more presynaptic neurons simultaneously These may cancel each other out, i.e. EPSP & IPSP adding together = no change Grand Postsynaptic Potential (GPSP) Composite potential on the postsynaptic membrane due to all EPSPs and IPSPs occurring at the same time Is the net change a depolarization that reaches threshold? “To fire or not to fire – that is the question.” If GPSP reaches threshold an action potential is generated at the axon hillock