How does a signal move from one neurone to another and how does this process change for different motor responses?

The transmission of an action potential- the signal- from one neurone to another occurs over the synapse. The structure of a synapse is as follows; there is a presynaptic bulb, a post synaptic bulb and the synaptic cleft between them. The action potential moves along the neurone by depolarisation (sodium influx) and repolarisation (potassium outflux), and is followed by a hyperpolarised refractory period. When that action potential reaches the presynaptic bulb, voltage gated ion channels open as a result of the depolarisation. These allow for the movement of calcium ions into the cell, causing vesicles containing neurotransmitters- most commonly acetylcholine- to be exocytosed into the synaptic cleft. These neurotransmitters bind to receptors on the post synaptic bulb that cause depolarisation in the attached, post synaptic neurone via the influx of sodium. The remaining neurotransmitter in the cleft is broken down by enzymes. Differences in this process can be seen in the different neurotransmitters used. In the motor pathways- also known as efferent, and the ones that initiate a response to stimuli- the somatic pathway (voluntary movement) uses the neurotransmitter acetylcholine, as does the parasympathetic autonomic pathway (responsible for the "rest and digest" response; gut peristalsis, increased urinary output, decreased heart rate). The sympathetic autonomic pathway however uses noradrenaline (this is responsible for the "flight or fight" response; pupil dilation, increased heart and respiratory rate).