What is the difference between an action potential and neurotransmitter release at a synapse?

• A. An action potential is the chemical signal across the synapse that influences the postsynaptic neuron
• B. Action potentials occur in glial cells; neurotransmitter release occurs in neurons
• C. An action potential is an electrical impulse along the neuron; neurotransmitter release is the chemical signal across the synapse that influences the postsynaptic neuron
• D. They are the same process

Answer: (C)

The main idea is that signaling in this part of the nervous system uses two different kinds of signals: an action potential and a neurotransmitter release, which are distinct steps in communication. An action potential is an electrical impulse that travels along the axon. It is generated by rapid changes in membrane polarity as voltage-gated Na+ and K+ channels open and close, and it moves down the neuron but does not itself cross the synapse.

When that electrical impulse arrives at the axon terminal, it triggers neurotransmitter release. This is a chemical signal: Ca2+ channels open, calcium enters, vesicles fuse with the presynaptic membrane, and neurotransmitters are released into the synaptic cleft. These chemicals then bind to receptors on the postsynaptic neuron, influencing its membrane potential and whether it fires an action potential.

So the difference is that the action potential is the electrical message traveling along the neuron, while neurotransmitter release is the subsequent chemical message across the synapse that affects the next neuron. The other statements mix up which signal is chemical versus electrical, or misstate where these processes occur (glial cells don’t typically generate the classic neuronal action potential).