Answer:
a. A nerve impulse occurs if the excitatory and inhibitory effects are equal.
Explanation:
A nerve impulse occurs when the summation of excitatory postsynaptic potential (EPSPs) from the presynaptic neurons is enough to reach the threshold level.
The excitatory effect of neurotransmitters causes depolarization of the postsynaptic membrane and brings it closer to the threshold to support nerve impulse.
On the other hand, the inhibitory graded potential causes hyperpolarization of the postsynaptic membrane and takes it closer to the resting stage. Hence, excitatory potential should be greater than the inhibitory potential to facilitate the nerve impulse.
