BGYB30H3 Lecture 3 Notes The Action Potential 1 Sep 17

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BGYB30H3 Lecture 3 Notes
-all cells try to maintain resting potential (nerve and muscle cells)
-these cells respond to changes in membrane permeability by opening and closing ion channels
-electrodes are used to give voltage readings through a voltmeter (able to measure differences in
membrane potential between IC and EC compartments
-membrane potential difference is relative to 0
-depolarization is that membrane potential is moving towards 0
-hyperpolarization is that membrane potential is moving more negative than resting membrane
potential
-repolarization is that membrane potential moves away from 0 to resting membrane potential
-sodium channel has inactive and active gate
-at rest, sodium active gate is closed and inactive gate is open
-depolarization involves opening active gate
-at 30mV, inactivation gate closes, in repolarization, activation gate closes
-sodium flux happens when both gates are open
-the two types of potassium channels are leak and non leak channels
-at RMP, leak channels are open and non leak are closed
-depolarization involves leak channels closed and non leak channels are opened
-hyperpolarization involves leak channels open and non-leak channels are closed
-potassium channels are slow to activate and inactivate
-sodium channels are quick to activate and inactivate
-changes in membrane potential are localized in the cell membrane while the rest of the cell is
negatively charged
-IC and EC are relatively stable
-oouuv}v]o}v[µu]Z}u}]ZvP
-axon hillock of the neuron is the trigger zone where action potentials occur and travel
-chemicals move up and down axon while electricity moves down axon
-myelin sheath insulates the neuron and is comprised of glial cells
-cell body collects and integrates info
-there is either fast or slow chemical signaling
-chemical signals such as peptides are packaged by the Golgi apparatus and sent down the axon
transport quickly
-microtubules direct flow of chemical messengers in the axon
-retrograde transport moves chemical signals back up axon to be broken down by lysosomes
-anterograde transport moves chemical signals down the axon to release vesicles
-at the synaptic junction, vesicles are released by exocytosis
-amplitude of graded potentials is directly proportional to the strength of the triggering signal
-graded potentials decrease in amplitude as it moves through the cell body by local current flow
-Ál]uµ]v]Ìu}À]vP}ÁvZoo}Çv}v[}µvction potential
- (-55mV) is the threshold to generate action potentials
-o}ÁZZ}o}v[Pv]}v}v]o
-Ál]uµ}v[Pv]}v}v]o](o}ÁZZ}o
-strong stimulus decreases in size but will be above threshold to generate action potential
-amplitude of action potential is not directly proportional to stimulus (once at threshold is reached,
same action potential no matter strength of stimulus)
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Document Summary

All cells try to maintain resting potential (nerve and muscle cells) These cells respond to changes in membrane permeability by opening and closing ion channels. Electrodes are used to give voltage readings through a voltmeter (able to measure differences in membrane potential between ic and ec compartments. Depolarization is that membrane potential is moving towards 0. Hyperpolarization is that membrane potential is moving more negative than resting membrane potential. Repolarization is that membrane potential moves away from 0 to resting membrane potential. At rest, sodium active gate is closed and inactive gate is open. At 30mv, inactivation gate closes, in repolarization, activation gate closes. Sodium flux happens when both gates are open. The two types of potassium channels are leak and non leak channels. At rmp, leak channels are open and non leak are closed. Depolarization involves leak channels closed and non leak channels are opened. Hyperpolarization involves leak channels open and non-leak channels are closed.

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