Answer:
some voltage-gated sodium channels are open
Step-by-step explanation:
In a neuron, a stimulus from a pre-synaptic neuron/sensory cell triggers the depolarization of the target cell toward the threshold of excitation ( i.e., the value where there is an initiation of an action potential). When this threshold is reached, sodium channels are opened and the membrane depolarizes, triggering an action potential. As soon as depolarization is complete, potassium channels are opened, sodium channels close and the neuron is hyperpolarized (.i.e., return to the resting potential).