Which neurotransmitter is known to function in both the central and peripheral nervous systems?

Acetylcholine (ACh) is the correct answer as it plays a crucial role in both the central and peripheral nervous systems. In the central nervous system (CNS), acetylcholine is involved in various functions, including memory and attention, influencing cognitive processes. In the peripheral nervous system (PNS), it serves as a neurotransmitter at neuromuscular junctions, where it facilitates muscle contraction by transmitting signals from motor neurons to muscle fibers. This dual functionality highlights the versatility of acetylcholine in coordinating complex responses throughout the body.

In contrast, dopamine mainly functions within the central nervous system and is associated with pleasure, motivation, and motor control but does not have a significant role in the peripheral nervous system. Norepinephrine, while it does operate in both systems, primarily functions as a hormone in the fight-or-flight response and is more prominent in the peripheral nervous system as part of the sympathetic nervous system. Serotonin is primarily found in the central nervous system and plays key roles in mood regulation, but it does not function in the peripheral nervous system to the same extent as acetylcholine. Understanding the role of neurotransmitters helps clarify their specific functions and importance in maintaining overall nervous system health and activity.