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PSU BIOL 240W - Ion Flow and Changes in Potential

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BIOL 240W 1st Edition Lecture 30Outline of Previous LectureI. NeuronsII. Nervous SystemOutline of Current LectureI. Changes in PotentialII. Nervous SystemCurrent LectureI. Changes in Potentiala. Sodium currents (into the cell) cause depolarizationsb. Potassium currents (out of the cell) cause hyperpolarizationsc. Opening and shutting of the channels (permeability) makes it easier or harder for ion flowi. Resistance- anything that makes it harder for current to flowii. Shutting ion channels increases resistanceII. Nervous Systema. Electrophysiology creates nerve impulses and actions potentialsb. There are presynaptic and post-synaptic neuronsc. Presynaptic neuron releases a neurotransmitter (ligand) that can bind to membrane protein on post-synaptic neuroni. Neurotransmitters are ligands because they bind to membrane proteinsii. Ligand-gated sodium channels exist on postsynaptic neuron1. Gated means that these channels can open and close2. Ligand-gated means that the presence of a bound ligand determines whether the channel is opened or closed3. When a neurotransmitter (ligand) binds to the ligand gated Na+ channel on the postsynaptic neuron, the channel opens4. When the channel is open, Na+ enters the postsynaptic neuron through the channel5. Na+ entering the postsynaptic neuron causes a depolarization up to the threshold voltagea. Threshold voltage- critical membrane voltage necessary for another set of ion channels (voltage-gated channels) to openiii. Voltage-gated channels1. There are sodium and potasium voltage-gated channelsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.2. Open sodium channels cause sodium to enter cell3. Open potassium channels cause potassium to exit cell4. Numerous channels exist on the axon hilloc, down the axon, and to the axon terminals5. Only open when the critical voltage has been reached6. Action potentials begin at axon hillock and spread down the axon. a. 2) open ligand gated sodium channels to depolarize from RMP to threshold voltagei. if threshold voltage is not reached, the voltage gated channels will not open and the sodium will get pumped out of the postsynaptic neuron, repolarizing to RMPb. 3) when threshold voltage is reached, the voltage gated channels open. Na+ channels open first (quickly) and K+ channels open slow. Giant increase is due to quick sodium channels***end of lecture after description of


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PSU BIOL 240W - Ion Flow and Changes in Potential

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