SIX BIG NAMES

The messengers you will see most

🔥

Glutamate

The main excitatory transmitter

🧊

GABA

The main inhibitory transmitter

🎯

Dopamine

Reward, motivation, and movement

🌙

Serotonin

Mood, sleep, and appetite

💪

Acetylcholine

Muscle control, attention, and memory

⚡

Norepinephrine

Alertness and the stress response

A handful of molecules carry a huge share of the brain's messages.

FAMILIES

Grouped by chemistry

Amino acids Glutamate, GABA, and glycine

Monoamines Dopamine, serotonin, and norepinephrine, made from amino acids

Choline-based Acetylcholine

Others Larger neuropeptides such as endorphins, and gases such as nitric oxide

Chemistry tells you how a transmitter is made and cleared.

SIZE

All small molecules

For comparison, an antibody is about 150,000 daltons.

All are under 200 daltons, tiny compared with a protein.

CHARGE

Charge decides how they behave

➕

Positive

Dopamine, serotonin, and norepinephrine carry a positive charge at body pH. Acetylcholine is permanently positive

➖

Negative

Glutamate carries a net negative charge at body pH

⚖️

Neutral overall

GABA has both a positive and a negative group, so it is roughly neutral

Charge matters for sensors, because many sense charge.

NOT ONE-TO-ONE

Meaning depends on the receiver

The same neurotransmitter can excite one cell and inhibit another, depending on which receptors that cell has. Many neurons also release more than one messenger at once. A transmitter is a word, and the receiver decides what it means.

The receptor, not the molecule, decides the effect.

UNIT 5 STUDY COMPLETE

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Ready for the Fab Challenge?

You've met the major neurotransmitters and seen why their small size and charge matter.