Final answer:
The concept not associated with a chemical synapse is neurotransmitters diffusing out of gap junctions as chemical synapses involve neurotransmitter release from synaptic vesicles into the synaptic cleft.
Step-by-step explanation:
The concept that is NOT associated with a chemical synapse is neurotransmitters diffusing out of gap junctions. A chemical synapse involves a specific structure known as the synaptic cleft, a tiny gap where neurotransmitters diffuse from the presynaptic neuron to the postsynaptic cell. These neurotransmitters are initially contained in synaptic vesicles within the axon terminal of the presynaptic neuron. Upon the arrival of an action potential, calcium ions trigger the fusion of these vesicles with the presynaptic membrane, releasing the neurotransmitters into the synaptic cleft. The neurotransmitters then cross the cleft to bind to receptor sites on the postsynaptic cell, which does not occur through gap junctions.
Furthermore, neurotransmitters binding to synaptic vesicles is not part of the normal function of a chemical synapse. Instead, synaptic vesicles release their neurotransmitter content into the synaptic cleft, not bind with it.