IPSPs (inhibitory postsynaptic potentials) A) block the efflux of potassium ions. B) increase membrane permeability to sodium ions. C) are local depolarizations. D) are local hyperpolarizations. E) block the efflux of calcium ions.

D) are local hyperpolarizations.

Explanation:

A neurotransmitter can trigger inhibitory or excitatory postsynaptic graded potentials. When a neurotransmitter causes hyperpolarization of the postsynaptic membrane, it is said to be inhibitory. When the postsynaptic membrane is hyperpolarized, it is more difficult to fire action potential since the inside of the membrane becomes more negative and is more away from threshold than from the resting state. This hyperpolarizing potential of the postsynaptic membrane is called inhibitory postsynaptic potential.