Question

The main ion responsible for the excitatory postsynaptic potential (EPSP) is:

1) Na⁺
2) K⁺
3) Cl⁻
4) Ca₂⁺
5) Cl⁻ or K⁺

Answer 1

Na⁺ (sodium) ions are responsible for excitatory postsynaptic potentials (EPSPs), as they cause depolarization of the postsynaptic neuron membrane, making it more likely to fire an action potential.

Step-by-step explanation:

The main ion responsible for the excitatory postsynaptic potential (EPSP) is Na⁺ (sodium). When neurotransmitters such as glutamate are released into the synaptic cleft, they bind to the ligand-gated ion channels on the postsynaptic neuron. This causes the sodium channels, which are integral parts of AMPA receptors, to open. As Na⁺ ions rapidly flow into the cell, they depolarize the membrane, and if the depolarization is strong enough, it can trigger an action potential in the neuron. In contrast, neurotransmitters like GABA, when binding to their respective receptors, cause Cl⁻ (chloride) channels to open, leading to hyperpolarization of the membrane and an inhibitory postsynaptic potential (IPSP), making it less likely that the neuron will fire an action potential.