How are nerve impulses transmitted across a synapse?

Nerve impulses travel in one direction from the pre-synaptic to the post-synaptic neuron across a gap called a synapse. This is done to continue a nerve impulse so that it can reach its destination in the body. The process requires the use of a neurotransmitter, one of the most common is acetylcholine (ACh). Firstly the action potential reaches the synaptic cleft (end of the neuron) in the pre-synaptic neuron, causing the opening of voltage-gated calcium channels. Therefore, there is an influx of calcium into the axon causing vesicles containing ACh to fuse with the synaptic membrane and release ACh. This ACh then diffuses from a high to low concentration towards the post-synaptic neuron and binds with nicotinic ACh receptors. The binding causes the opening of ligand-gated sodium channels and therefore an influx of sodium into the post-synaptic axon to continue the impulse. Following this, ACh is broken down by acetylcholinesterase into acetyl and choline which both diffuse back to the pre-synaptic neuron ready to transmit future impulses.