Question

9. 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 an initial membrane potential of -70 mV, the net effect of the simultaneous arrival of six IPSPs and two EPSPs would be to move the membrane potential to

A. -72 mV

B. -68 mV

C. -71 mV

D. -70 mV

Answer 1

Correct answer is A. -72mV

if 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 an initial membrane potential of -70 mV, the net effect of the simultaneous arrival of six IPSPs and two EPSPs would be to move the membrane potential to -72 mV.

Because Simultaneous arrival of six IPSPs (6 X -0.5 = -3mV) and two EPSPs (2 X 0.5 = 1mV) occur, then the net effect on membrane potential will be -70 + (-3 +1) = -70 + (-2) = -70-2 = -72 mV

therefore the memrane potential decrease by 2 mV