試題詳解

3. Which of the following best explains why a neuron receiving a simultaneous excitatory postsynaptic potential (EPSP) and inhibitory postsynaptic potential (IPSP) may fail to reach the threshold for an action potential?
(A) The IPSP causes a transient inactivation of voltage-gated Nat channels, making depolarization impossible.
(B) The inhibitory synapse stabilizes the membrane potential at a level too positive to allow Na+ channel activation.
(C) The summation of EPSP and IPSP results in a net change in membrane potential that may be insufficient to reach the threshold.
(D) The presence of an IPSP leads to immediate degradation of neurotransmitters, reducing excitatory drive.
(E) The inhibitory synapse actively removes Nat from the postsynaptic cell, counteracting the excitatory input.