Which of the following correctly places the events of an excitatory postsynaptic potential (EPSP) in order?

• A. Binding to postsynaptic receptors → Neurotransmitter release → Influx of Na\(^+\) ions → Opening of ligand-gated ion channels → Membrane depolarization
• B. Neurotransmitter release → Influx of Na\(^+\) ions → Binding to postsynaptic receptors → Opening of ligand-gated ion channels → Membrane depolarization
• C. Opening of ligand-gated ion channels → Neurotransmitter release → Binding to postsynaptic receptors → Influx of Na\(^+\) ions → Membrane depolarization
• D. Neurotransmitter release → Binding to postsynaptic receptors → Opening of ligand-gated ion channels → Influx of Na\(^+\) ions → Membrane depolarization

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the sequence of events in an excitatory postsynaptic potential (EPSP). EPSPs occur when neurotransmitters released by the presynaptic neuron bind to receptors on the postsynaptic neuron, leading to a series of events that result in membrane depolarization.
2. Step 2: Begin with the first event: neurotransmitter release. Neurotransmitters are released from the presynaptic neuron into the synaptic cleft in response to an action potential.
3. Step 3: Next, the neurotransmitters bind to specific postsynaptic receptors located on the membrane of the postsynaptic neuron. This binding is crucial for initiating the subsequent steps.
4. Step 4: Binding of neurotransmitters to postsynaptic receptors triggers the opening of ligand-gated ion channels. These channels are specific to certain ions and open in response to the chemical signal provided by the neurotransmitter.
5. Step 5: Once the ligand-gated ion channels open, there is an influx of Na\(^+\) ions into the postsynaptic neuron. This influx causes the membrane potential to become less negative, leading to membrane depolarization, which is the hallmark of an EPSP.