The diagram illustrates a synapse within a reflex arc. Which two neurones are shown, and in what direction does the neurotransmitter move?
- Aneurone P: motor; neurone Q: relay; direction: $P \rightarrow Q$
- Bneurone P: motor; neurone Q: sensory; direction: $P \rightarrow Q$
- Cneurone P: relay; neurone Q: motor; direction: $Q \rightarrow P$
- Dneurone P: relay; neurone Q: sensory; direction: $Q \rightarrow P$