Neuroscience problem

[InquilineKea]

Hm so I'm having difficulty in answering this question. This is what I have so far:

 

1. The problem statement, all variables and given/known data

 

Consider a neuron with resting potential of -65 mV and threshold of -55 mV. It receives two

synaptic inputs with similar synaptic conductances, one with reversal potential of -10 mV and the

other with reversal potential of -58 mV. Draw the predicted postsynaptic response (change in

membrane potential) to stimulation of each synapse alone, and then to simultaneous stimulation of

both synapses. Briefly explain what’s going on and why the results might at first be confusing.

 

3. The attempt at a solution

 

So the neuron will reach an action potential at -55 mV. So if the neuron gains 10 mV, it will depolarize and reach an action potential. Now, how will the synaptic inputs affect the neuron? Input 1 might have a reversal potential of -10 mV, but that doesn't say how much current it sends to the neuron, nor does it say the proportion of total positive/negative ions in the input compared to that of the neuron. So that confuses me. How do we add potentials? Do we just take some average of the resting potential of the neuron with the reversal potential of the inputs? Which would be sort of like adding up concentrations or ratios. Or do we add-55 to -10 and -55 to -58? Ions sum up additively (and don't involve taking ratios) but I highly doubt the question wants me to say that since then there would just be hyperpolarization and no action potential for either input.

 

Thanks!

[zule]

I think you are confused about the term “reversal potential”. For a certain neurotransmitter, it is the potential which the net movement of charges will be zero.

 

When the membrane potential is more negative than the reversal potential , the net movement of charges caused by this neurotransmitter will do the membrane potential more positive. But once the potential of membrane is the same as the reversal potential, the net current flow of ions will be zero.

 

If the membrane potential gets more positive than the reversal potential, the net movement of charges caused by the neurotransmitter will do the membrane potential more negative.