What is the purpose of axonal terminals releasing neurotransmitter?

• A. To deliver myelin to axons.
• B. To convey signals to the postsynaptic cell by binding receptors.
• C. To generate ATP for the neuron.
• D. To produce action potentials in the presynaptic neuron.

Answer: (B)

Chemical signaling at a synapse hinges on releasing neurotransmitters when an action potential arrives at the axon terminal. The incoming signal opens calcium channels, causing vesicles filled with neurotransmitter to fuse with the presynaptic membrane and release their contents into the synaptic cleft. The neurotransmitter then binds to receptors on the postsynaptic cell, opening ion channels or triggering intracellular signals that alter the postsynaptic membrane potential and propagate the message. So, the main purpose of releasing neurotransmitter is to convey signals to the postsynaptic cell by binding its receptors and generating a response. For contrast, delivering myelin insulates axons, producing ATP is a general energy function, and action potentials are generated in the presynaptic neuron as part of the signaling process rather than the direct purpose of transmitter release.