Acetylcholine (ACh) function

enables muscle action, learning, and memory. malfunction: with Alzheimer’s disease, ACh-producing neurons deteriorate.

Dopamine function

influences movement, learning, attention, and emotion. malfunction: oversupply linked to schizophrenia; undersupply linked to tremors and decreased mobility in Parkinson’s disease.

Serotonin function

affects mood, hunger, sleep, and arousal. malfunction: undersupply linked to depression; some drugs that raise serotonin levels are used to treat depression.

Norepinephrine function

helps control alertness and arousal. malfunction: undersupply can depress mood.

GABA (gamma-aminobutyric acid) function

a major inhibitory neurotransmitter. malfunction: undersupply linked to seizures, tremors, and insomnia.

Glutamate function

a major excitatory neurotransmitter; involved in memory. malfunction: oversupply can overstimulate the brain, producing migraines or seizures.

Endorphins function

neurotransmitters that influence the perception of pain or pleasure. malfunction: oversupply with opioid drugs can suppress the body’s natural endorphin supply.

Substance P function

involved in pain perception and immune response. malfunction: oversupply can lead to chronic pain.