What chemical is released at the presynaptic membrane to transmit action potentials across a synapse?

The chemical that is released at the presynaptic membrane to transmit action potentials across a synapse is a neurotransmitter. When an action potential reaches the axon terminal of a neuron, it triggers the opening of voltage-gated calcium channels. The influx of calcium ions causes synaptic vesicles filled with neurotransmitters to fuse with the presynaptic membrane, releasing these chemicals into the synaptic cleft.

Neurotransmitters then bind to specific receptors on the postsynaptic membrane, leading to the propagation of the signal in the next neuron. This process is crucial for communication between neurons in the nervous system. Neurotransmitters are essential for various functions, including mood regulation, motor control, and sensory perception. Understanding their role in synaptic transmission is fundamental in biology and neuroscience, as it connects to how information is processed in the nervous system.

Other choices do not serve the role of transmitters across synapses. Receptors are proteins that bind neurotransmitters but are not themselves released. Hormones are signaling molecules that typically travel through the bloodstream to target organs, rather than transmitting signals across synapses directly. Enzymes catalyze biochemical reactions but do not play a direct role in the transmission of neuronal signals across synaptic gaps