Lecture 32 notes - Lecture 32: Synapses 1056-1063.Chapter...

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Lecture 32: Synapses 1056-1063…Chapter 48 48.4 Neurons Communicate with Other Cells at Synapses -when an action potential reaches the terminals of an axon, it generally stops (most cases: action potentials are not transmitted from neurons to other cells…but INFO is transmited from neurons to other cells) -some synapses, electrical synapses contain gap junctions which do allow electrical current to flow directly from cell to cell…majority: chemical synapses (release of chemical neurotransmitter) - synaptic vesicles : stored in neuron’s synaptic terminals which is where the presynapitc neuron synthesizes the neurotransmitter -many synaptic terminals may interact with the cell body and dendrites of a postsynaptic neuron -when an action potential reaches a synaptic terminal, it depolarizes the terminal membrane, opening voltage-gated calcium channels in the membrane -calcium ions diffuse into terminal and then rise in ca_ concentration in the terminal causes some of the synaptic vesicles to fuse with the ther terminal memrane, releasing the neurotrasmitter by exocytosis -neurotramsitter diffuses across the synaptic cleft , a narrow gap that separates the presynaptic neuron from the postsynaptic cell -chemical synapse: 1- when an action potential depolarizes the plasma membrane of the synaptic terminal, it 2- opens the voltage gated calcium channels in the membrane triggering an influx of ca2+ 3- the elevated ca2+ concentration in the terminal causes synaptic vesicles to fuse with the presynaptic membrane 4- the vesicles release neurotrasmitter into the synaptic cleft 5- the neurotransmitter binds to the receptor portion of ligand gated ion channels in the postsynaptic membrane, opening the channels. In the ysnapse iboth na and k can diffuse throught he cahnnels 6- the neurotrasmitter is released from the receptors and the channels close. Synaptic transmisstionion ends when the neurotransmitter diffuse out of the synaptic cleft, is taken up by the synaptic terminal or by another cell, or is degraded by an enzyme -info transfer is much more modifiable at chemical synapses than at electrical synapses…many factors can affect the amount of neurotransmitter that Is released or the responsiveness of the postsynaptic cell…such modifications underlie an anaimal’s ability to alter its behavior in response to change and form the basis for learning and memory Generation of Postsynaptic Potentials -ligand gated ion channels are capable of binding to the neurotransmitter are clustered in the membrane of the postsynaptic cell, directly opposite the synaptic terminal -the receptor opens the channel and allows specific ions to diffuse across postsynaptic
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Lecture 32 notes - Lecture 32: Synapses 1056-1063.Chapter...

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