Explain the process of synaptic transmission, beginning with the neurotransmitters at the axon terminal of the presynaptic cell and ending with the impulse being sent down the postsynaptic cell.

The synapse is actually the link between 2 neurons. Now when an action potential contacts the synaptic knob of a neuron, the voltage-gate calcium channels are unlocked, resulting in an influx of positively charged calcium ions into the cell. This makes the vesicles containing neurotransmitters, for example acetylcholine, to travel towards the pre-synaptic membrane. When the vesicle arrives at the membrane, the contents are released into the synaptic cleft by exocytosis. Neurotransmitters disperse across the space, down to its concentration gradient, up until it reaches the post-synaptic membrane, where it connects to the correct neuroreceptors. Connecting to the neuroreceptors results in depolarisation in the post-syanaptic neuron as voltage-gated sodium channels are also opened, and the positively charged sodium ions travel into the cell. When adequate neurotransmitters bind to neuroreceptors, the post-synaptic membrane overcame the threshold level of depolarisation and an action potential is made and the impulse is transmitted.

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