What is the correct order for the events of neurotransmitter release from the synaptic terminal? 1 – Extracellular Ca2+ enters terminal and binds to sensor protein in the cytoplasm 2 – Exocytosis of neurotransmitter into synaptic cleft 3 – Action potential reaches axon terminal 4 – Ca2+-protein complex stimulates fusion of the docked synaptic vesicle with the plasma membrane 5 – Voltage-gated Ca2+ channels open

When the action potential (AP) reaches the axon terminal, the membrane is depolarized, leading to the opening of the Ca2+ channels. Ca2+ outside of the terminal can now enter through the voltage-gated Ca2+ channels. This Ca2+ binds to the sensor protein which forms a protein complex that stimulates fusion of synaptic vesicles with the plasma membrane of the synaptic terminal. After fusion, exocytosis or release of the neurotransmitter that was in the synaptic vesicles occurs.

The neurotransmitters can then bind to receptors to carry on the transmission of the message the action potential is carrying.