What happens to an action potential at an excitatory synapse? A)The postsynaptic neuron depolarizes the presynaptic cell membrane. B)The presynaptic neuron increases the permeability of the subsynaptic membrane of the postsynaptic cell to both Na⁺ and K⁺. C) The presynaptic neuron increases the permeability of the subsynaptic membrane of the postsynaptic cell to K⁺ only. D) A small hyperpolarization occurs.

Question

Quizplus · Accepted Answer

At an excitatory synapse, the presynaptic neuron releases neurotransmitters such as glutamate, which bind to receptors on the subsynaptic membrane of the postsynaptic neuron. This binding causes an influx of both Na+ and K+ ions, which depolarizes the postsynaptic membrane potential and results in an action potential. Therefore, the presynaptic neuron increases the permeability of the subsynaptic membrane of the postsynaptic cell to both Na+ and K+ ions. Choice A is incorrect because the postsynaptic neuron cannot depolarize the presynaptic cell membrane (only the opposite direction is possible). Choice C is incorrect because the permeability of the subsynaptic membrane is increased for both Na+ and K+ ions, not just K+. Choice D is incorrect because a small hyperpolarization occurs at inhibitory synapses, not excitatory synapses.

What Happens to an Action Potential at an Excitatory Synapse