Neurotransmitters act as chemical messengers in the nervous system, essential for communication between neurons. They regulate physiological and psychological processes, including mood, memory, sleep patterns, and heart rate. There are various neurotransmitters, each with specific functions. For instance, serotonin, associated with well-being and happiness, influences mood, appetite, and sleep. Imbalances in serotonin levels can lead to depression and sleep issues. Dopamine, central to the reward system, affects pleasure and motivation. Dysregulation of dopamine is linked to Parkinson's disease and schizophrenia. In contrast, GABA is the brain's primary inhibitory neurotransmitter that reduces excitability. Low levels of GABA are linked with seizures, tremors, and insomnia. Acetylcholine supports muscle activation and cognitive functions such as memory and attention. Imbalances in acetylcholine are associated with Alzheimer's disease. Norepinephrine relates to attention and stress response. It is crucial for the fight–or–flight reaction and influences alertness and blood pressure during stress. Low levels of norepinephrine may lead to depression.