Neurons talk to each other by releasing chemical messengers called neurotransmitters. Pick a messenger, press Release, and watch what happens to the cell that receives it.
What's happening?
- A signal arrives. An electrical signal (an action potential) travels down the first neuron to its tip.
- Calcium rushes in. The signal opens calcium (Ca²⁺) channels, and calcium flows into the tip.
- Vesicles release the messenger. Calcium makes the little bubbles (vesicles) fuse with the edge of the cell and spill out neurotransmitter.
- The messenger crosses the gap. It drifts across the tiny gap between the cells (the synaptic cleft) and fits into receptors, like a key in a lock.
- The receiving cell responds. Depending on the receptor, the cell gets a push toward firing (excited) or a nudge away from it (inhibited). Watch the voltage chart.
- Clean-up. Proteins pull the messenger back in or break it apart, so the signal doesn't last forever. (For glutamate, most of the clean-up is actually done by nearby support cells called astrocytes. The model shows it on the sending neuron to keep things simple.)
Try this
Pick Glutamate and press Release a few times quickly. Can you push the voltage over the dashed line and make the cell fire? Now pick GABA. What happens to the voltage instead?
Pick Serotonin and turn on the drug (an SSRI, a common antidepressant). Watch how long the messenger hangs around in the gap.
Keep in mind
This is a simplified model. Real synapses work hundreds of times faster than shown here, a single synapse changes the voltage much less, and real cells carry many kinds of receptors at once.