Assume that a single IPSP has a negative magnitude of - 0.5 mV at the axon hillock, and that a single EPSP has a positive magnitude of + 0.5 mV. For a neuron with initial membrane potential is -70 mV, the net effect of the simultaneous arrival of 6 IPSPs and 2 EPSPs would be to move the membrane potential to
A)-72 mV.
B)-71 mV.
C)-70 mV.
D)-69 mV.
E)-68 mV.

Question

Quizplus · Accepted Answer

Each IPSP will result in a decrease of 0.5 mV in the membrane potential, whereas each EPSP results in an increase of 0.5 mV. Therefore, the simultaneous arrival of 6 IPSPs and 2 EPSPs would result in a net decrease in membrane potential of 4 mV (6 x -0.5 mV + 2 x 0.5 mV = -3 mV + 1 mV = -2 mV). 
Starting with a membrane potential of -70 mV, the net effect would be to move the membrane potential to -72 mV (-70 mV - 2 mV = -72 mV). Therefore, the best choice is A) -72 mV.

Assume That a Single IPSP Has a Negative Magnitude of -