Final answer:
Serotonin is a neurotransmitter synthesized from tryptophan that is found in all animal taxa. It plays a role in regulating mood, sleep, appetite, and pain sensitivity. It is important for the functioning of the central nervous system.
Step-by-step explanation:
Serotonin, which is synthesized from the amino acid tryptophan, is a neurotransmitter found in all animal taxa. It is a monoamine neurotransmitter that plays a role in various functions in the central nervous system and cardiovascular tissue. Serotonin is involved in regulating mood, sleep, appetite, and pain sensitivity. It is also known as 5-hydroxytryptamine (5-HT) and is an important target in the treatment of depression and anxiety disorders.