Final answer:
The most common neurotransmitter in the peripheral nervous system is acetylcholine, which is the primary neurotransmitter at neuromuscular junctions.
Step-by-step explanation:
The most common neurotransmitter in the peripheral nervous system is acetylcholine (E). It is released at the neuromuscular junctions and is responsible for triggering muscle contractions. The cholinergic system, which relies on acetylcholine as its neurotransmitter, is predominant within certain areas of the nervous system, including the peripheral nervous system. While other neurotransmitters such as norepinephrine and dopamine play significant roles in the nervous system, acetylcholine is the primary neurotransmitter at neuromuscular junctions in the peripheral nervous system.
Glycine and aspartate are primarily associated with neurotransmitter systems in the central nervous system (CNS), such as the glycinergic, and glutamatergic systems respectively. Substance P is involved in pain perception and is released in response to noxious stimuli.