Final answer:
The opening of nicotinic cholinergic receptors, which allow both Na+ and K+ to move across the membrane, will lead to an excitatory postsynaptic potential (EPSP), depolarizing the postsynaptic neuron and making it more likely to fire an action potential.
Step-by-step explanation:
When nicotinic cholinergic receptors on the plasma membrane bind to acetylcholine, they open ion channels that allow both Na+ and K+ to move across the membrane. The influx of Na+ causes a depolarization of the postsynaptic membrane, leading to an excitatory postsynaptic potential (EPSP), which makes the postsynaptic neuron more likely to fire an action potential. On the other hand, an inhibitory postsynaptic potential (IPSP) causes hyperpolarization, making the neuron less likely to fire an action potential, commonly involves the movement of Cl- ions into the cell.
In this case, the opening of nicotinic cholinergic receptors that allow passage of both Na+ and K+ would lead to an EPSP, as the overall effect is to depolarize the postsynaptic membrane. This is similar to what happens at the neuromuscular junction, where the influx of Na+ through nicotinic cholinergic receptors leads to muscle contraction.