Final answer:
Serotonin is the neurotransmitter involved in emotional arousal and sleep among the options given. It plays a key role in mood regulation and sleep cycles, affecting various psychological and bodily functions.
Step-by-step explanation:
Among the neurotransmitters listed, serotonin is involved in emotional arousal and sleep. Dopamine plays a role in reward and motivation, acetylcholine is significant for muscle activation and memory, and GABA (gamma-aminobutyric acid) is primarily an inhibitory neurotransmitter that calms neuronal activity.
The neurotransmitter serotonin affects a variety of psychological and bodily functions, including mood, desire, appetite, sleep, memory, learning, temperature regulation, and some behaviors. An imbalance in serotonin levels can lead to mood disorders such as anxiety and depression. Thus, serotonin closely ties to both emotional states and sleep cycles.
While dopamine, acetylcholine, and GABA are also critical neurotransmitters within the brain, they are more specifically associated with other primary functions and effects. However, during the processes involving cognition and the central nervous system, these neurotransmitters might intersect with roles in emotion and sleep indirectly. Serotonin is singularly noted for its direct connection to emotional arousal and sleep regulation.