US High School Psychology Practice Exam 2026 – Your All-in-One Guide to Exam Success!

The neurotransmitter that plays a crucial role in regulating mood and sleep is serotonin. Serotonin is known for its involvement in a variety of functions, including the regulation of mood, anxiety, and happiness. It helps to stabilize mood and contributes to feelings of well-being and happiness. Furthermore, serotonin has a significant impact on sleep cycles, particularly in promoting sleep and regulating sleep rhythms.

This neurotransmitter is synthesized from the amino acid tryptophan and is primarily found in the brain, intestines, and blood platelets. Disruptions in serotonin levels can lead to mood disorders such as depression and anxiety, highlighting its essential role in emotional regulation. Additionally, serotonin's influence on sleep is linked to its role in regulating the sleep-wake cycle, as it is involved in the synthesis of melatonin, which is critical for sleep regulation.

In contrast, the other neurotransmitters have different primary functions. Dopamine is mainly associated with pleasure, reward, and motor control; acetylcholine is involved in muscle activation and memory; and norepinephrine primarily affects attention and responding actions in the brain. Each neurotransmitter has specific roles that do not focus primarily on mood and sleep in the same way that serotonin does.