IB Psychology – Biological Approach Practice Test

Excitatory neurotransmitters are the chemicals that carry signals across the synapse to the next neuron and make the postsynaptic membrane more likely to fire. When released into the synaptic gap, they bind to receptors and depolarize the postsynaptic cell, creating an excitatory postsynaptic potential (EPSP). This depolarization brings the neuron closer to the threshold for an action potential, producing a stimulating effect in brain activity. Inhibitory neurotransmitters, by contrast, hyperpolarize the membrane and decrease firing. Agonists and antagonists affect receptor activity but the direct carriers of the signal that promote stimulation are the excitatory neurotransmitters.