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Homework Help: Intro to Neuroscience

  1. Sep 25, 2009 #1


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    I need a little help with this assignment from my neuroscience class. I have tried to answer them but I'll like to know if my reasoning is right or wrong. I had to use the Neurons in Action software at school for some simulations but I think most of the questions could be answered without it.

    First problem:
    By changing the membrane capacitance to values of 1, 2, 5, 10 and 100 (microFarad/cm2), the Vm across the membreane would decrease as the membrane capacitance increases. This due to the fact that the membrane's ability to hold a charge is increased and the electrical charge across the membrane is lowered.

    By adding the leak channels to the bilayer membrane, the electrical current "decays" faster and the time constant is larger, making the speed of responses slow. No idea about an example, any help with this part would be appreciated.

    By adding the HH pump, the capacitve current density increases. The membreane threshold decreases. When the membrane capacitance has a value of 10 microFarad/cm^2 and the density of Na and K channels increased by tenfold, there is no change since everything increased by tenfold. Definetely not sure if this is right or not.

    a) Using the Goldman equation, the Vrest is -55 mV. Not sure how to calculate this Vrest.
    b) It would increase the resting potential from -55 to -28 mV.
    c) Using thi formula Vrest = (gKEK + gNaENa + gClECl)/(gK + gNa + gCl), the Vrest is -31.96 mV. I think a and c should match so one of them is worng, but sure which one.

    I do not expect you guys to just tell me the anwer straight foward but any help would be appreciated. I have until wednesday to hand in this assignment and tuesday I'll try to redo the simulations with the software and double check.

  2. jcsd
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