Key ideas

• Neurons don't touch; when an action potential reaches the end of an axon, neurotransmitters are released, cross the synapse, and bind to receptors on the receiving neuron.
• Neural communication is both electrical (the action potential within a neuron) and chemical (neurotransmitters between neurons).
• Excitatory messages make a neuron more likely to fire and inhibitory messages act like a brake; the neuron fires only if the total pushes it past threshold.
• After delivering their message, neurotransmitters must be cleared from the synapse, and one way is reuptake by the neuron that released them.
• AP Psychology requires eight neurotransmitters, listed below under key terms, each with different functions depending partly on where it acts in the nervous system.

Key terms

synapse

The tiny gap between one neuron and the next.

neurotransmitters

Chemical messengers stored at the ends of neurons that carry messages across the synapse.

receptors

Sites on the receiving neuron where neurotransmitters bind.

excitatory

Describes neurotransmitter messages that make the receiving neuron more likely to fire.

inhibitory

Describes neurotransmitter messages that make the receiving neuron less likely to fire, acting like a brake.

reuptake

When neurotransmitters are taken back up by the neuron that released them, clearing the synapse.

dopamine

Key to the brain's reward system, driving motivation and learning from rewarding experiences; also important for movement.

serotonin

Especially important for regulating mood; also involved in sleep and appetite.

norepinephrine

Involved in alertness and arousal.

glutamate

A major excitatory neurotransmitter.

GABA

A major inhibitory neurotransmitter.

substance P

Helps transmit pain information.

endorphins

Help reduce pain.

acetylcholine

Important for muscle movement and memory; in myasthenia gravis it can't communicate effectively with muscles, causing weakness.

Watch out