The Brain's Chemical Messengers
Different neurotransmitters specialize in distinct jobs to keep your mind and body running.
Acetylcholine (ACh) activates skeletal muscle and supports memory; its loss is linked to Alzheimer's disease. Dopamine drives reward and motivation. Too little in the substantia nigra causes Parkinson's disease, while excess triggers schizophrenia symptoms.
Serotonin regulates mood, sleep, and appetite, and is targeted by SSRIs for depression. Norepinephrine promotes arousal and alertness for the fight-or-flight response.
Excitatory vs Inhibitory Traffic
Glutamate is the main excitatory transmitter essential for learning. GABA is the main inhibitory transmitter that dampens neural excitability. Endorphins act as natural opioid painkillers.
| Term | Effect on Receptor | Example |
|---|---|---|
| Agonist | Mimics or enhances effect | Nicotine mimics ACh |
| Antagonist | Blocks or reduces effect | Curare blocks ACh |
Pitfall: Never assume an antagonist does nothing. Blocking a receptor has dramatic effects, like naloxone reversing an overdose.