Bio2 Lecture 5 - Bio2 Lecture 5 Nerve Impulses are action...

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Bio2 Lecture 5 2/1/05 Nerve Impulses are action potentials - We watch to see the charge change over time - Cell pumps ions, sodium and potassium ions - Sodium ions go out - Potassium ions go in - Ratio is 3:2, 3 sodium ions out for every 2 potassium ions in - Potassium also leak a lot, but sodium leak much less - At -55mV which is the threshold, once it crosses, then voltage activated sodium ion channels open, and its like opening the flood gates, and the voltage spikes up. - At 35 mV the voltage activated potassium ion channels begin to open, the exact voltage isn’t important - Action potential is unidirectional o Built in refractory period prevents everything from going the wrong way o All or nothing response, cannot be a larger or smaller action potential, they are all created equal o They are all the same with regard to their magnitude o Are being regenerated along the way o Action o potential is propagated all along the axon, like a wave, and if you isolate the axon it may be resting phase or middle of action potential, and occurs smoothly o Axons are like a chains and when nerve impulses go off the message travels like a wave down the line o They can find voltage by creating a small micropipette, then isolating a small patch of cell membrane. Then hope you get 1 ion channel, take that piece of tissue, and put in all sorts of ions and record the data, do experiment many times to make sure you got 1 ion channel - This has all been for unmylinated axon -
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