Midterm 1 Study

Midterm 1 Study - 5. Synapses a response that inhibits the...

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5. Synapses Neurons release a neurotransmitter onto a target cell. Chemical synapse: the site of transmitter release, diffusion, and binding to the target cell Pre-synaptic cell - transmitter releasing cell Post-synaptic cell - target cell, can be neuron.muscle.or epithelial cell Convergence: presence of more than one synapse onto a neuron Divergence: when a single pre-synaptic cell forms synapses onto more than one postsynaptic cell. Neurotransmitter release 1) depolarization of axon terminal 2) CA influx through voltage-gated Ca channels - > rise in Ca influx leads to exocytosis of vesicles 3) transmitter diffuses across cleft and binds to receptors 4) this leads to gating (opening or closing) of channels in the postsynaptic cell Transmitter-gated channels: neurotransmitters affect the post-synaptic cells by increasing the tendency of channels to open or close • if enough transmitter-gated channels open or close, the overall permeability of the postsynaptic cell can change, thus Em will change EPSP (excitatory postsynaptic potential) • the postsynaptic cell will depolarize • by moving the cell thoward threshold, the chance of spiking increases, this tends to excite the postsynaptic cell IPSP • a response that inhibits the postsynaptic cell • it decreases the probability it will spike • typically IPSPs are hyperpolarizations. Moves the membrane potential away from spike threshold • can be causes by an increase in Pk OR a decrease in Pna Disinhibition - the removal of inhibition 3 Ways to remove transmitters from synaptic cleft: diffusion, uptake into nearby glia, degradation by an enzyme Uptake into nearby glia: secondary active transport. Carrier protein binds Na ions and the transmitter, and releases them into the cytoplasm of the glial cell Degradation by an enzyme: enzymes bind to transmitter and hydrolize it to other chemicals that do not activate the receptors How do cells stop transmitter release?
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This note was uploaded on 01/31/2012 for the course NPB 101 taught by Professor Fuller,charles/goldberg,jack during the Summer '08 term at UC Davis.

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Midterm 1 Study - 5. Synapses a response that inhibits the...

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