Final answer:
Inhibitory neurotransmitters such as glycine and GABA make a postsynaptic cell harder to depolarize by allowing an influx of Cl- ions.
Step-by-step explanation:
Inhibitory neurotransmitters such as glycine and GABA make a postsynaptic cell harder to depolarize by allowing an influx of Cl- ions.
When these inhibitory neurotransmitters are released from a presynaptic neuron, they bind to and open Cl- channels. The entry of Cl- ions into the postsynaptic cell hyperpolarizes the membrane, making the neuron less likely to fire an action potential.
On the other hand, allowing an influx of Na+ or K+ would have excitatory effects and depolarize the postsynaptic cell, making it easier to fire an action potential.