NPB 100 Lecture 8

NPB 100 Lecture 8 - -the connexons form a tube between the...

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-the connexons form a tube between the two cells -hexameric arrays of 6 subunits (1 subunit is 1 connexon protein) -in addition to inward transient Na currents -some cells express a slower noninactivating inward Na current -Calcium currents -L-type long lasting activation -T for transient, they’re short -N and T differs on when they first turn on -Potassium currents -C-current is Ca-gated, slower activation but persistent -A-current, shaker current, fast activation and inactivation -M-current -Muscarinic, another K current, slow activation but persistent -H-current -enables recriprocal inhibitory synapses to work -voltage step from -10 to -100 activates this current -a cation current -activated by hyperpolarization -slide 4. Cell in the center has only Na current and K current. If depolarize it with a step of current, membrane potential depolarizes and it starts to fire regularly -if you introduce one at a time a small amount of the other currents -if you introduce the A current, delays the spike, slows down the firing rate -introduce C current, a slower current but does activate with voltage. The firing pattern chages. Smaller number of spikes. Get big hyperpolarization followed by each spike. -M current, cell stops responding very much -persistent K current, firing rate of the cell drop. An example of accomodation -T-current. Ca voltage-gated current. Slow to turn on but it stays on. Gets a burst of spikes that persists. Inactivates with depolarization.
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-post-inhibitory rebound -strenght of burst that follows depend on how long and big the period of hyperpolarization is -will show simulations of neurons that show synaptic organization or not and Ih or not -will be plots of membrane potential here and time going in the other direction -one cell will be black and the other will be red -initially will show these cells going along (they have slightly different currents going in them so they fire at slightly different frequency) -they go along, heres one firing an action potential (that is a black action potential), here is a red one, bang!, black one fires at a lower frequency as you shall see. These things are completely independent of each other. -We can regard them as our red cell and our black cell sitting there side by side and the action potential of the two have no effect on each other because there are no electrical synapses between them. -as you shall see here, as the simulation proceeds, we wind up with twice as many red spikes as black ones (so racist! lol). -next simmulation: in this case, the 2 cells have identical membranes and starting at slightly different time. They start off and they go on and fire at the same frequency. At 1 second along here, 2 synapses (1 from red onto black and 1 from black onto red) will be turned on. At this point, something happens. Watch as how their firing changes. Black didn’t fire there, didn’t fire again. Get 2 red spikes. Red. There’s black. Red. Black. They settle into a pattern of firing alternating spikes. These things which have been firing at different times are now firing at precise
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This note was uploaded on 03/15/2010 for the course NPB NPB taught by Professor Bales during the Winter '09 term at UC Davis.

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NPB 100 Lecture 8 - -the connexons form a tube between the...

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