Which of the following is false or incorrect?

a. A nerve impulse occurs if the excitatory and inhibitory effects are equal.

b. An excitatory postsynaptic potential occurs if the excitatory effect is greater than the inhibitory effect but less than threshold.

c. An inhibitory postsynaptic potential occurs if the inhibitory effect is greater than the excitatory, causing hyperpolarization of the membrane.

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.