Final answer:
In the central nervous system, excitatory neurotransmitters generally open sodium (Na+) channels, leading to the depolarization and the generation of excitatory postsynaptic potentials (EPSPs), which increase the likelihood of neuron firing an action potential.
Step-by-step explanation:
Excitatory neurotransmitters of the CNS usually act by opening Na+ channels.
Excitatory neurotransmitters in the central nervous system (CNS) typically function by opening specific types of ion channels that allow for the passage of certain ions into the postsynaptic neuron. The most common action is the opening of sodium (Na+) channels, which leads to depolarization and the potential for an action potential to be generated in the neuron.
When a neurotransmitter binds to a receptor on the postsynaptic membrane, which are ligand-gated channels, it causes an ion channel to open, letting Na+ ions enter the cell. The influx of Na+ ions results in a change in the electrical potential of the postsynaptic cell, which can create an excitatory postsynaptic potential (EPSP), making it more likely that the neuron will fire an action potential.
Other ions like K+, Cl-, Ca2+, and H+, while also important in neuronal function, do not typically result in excitatory postsynaptic potentials when their respective channels are activated by neurotransmitters. For example, K+ contributes to the restoration of membrane potential after an action potential, and Ca2+ ions are crucial for initiating neurotransmitter release at the synaptic cleft.