What happens at a synapse?

Change input strength and frequency to see when the receiving neuron fires.

Press Play to begin.

Where the signals occur

Two branching neurons connected by a chemical synapseAn input spike triggers transmitter release. Transmitter opens ion channels on a receiving dendrite. The receiving neuron can fire after its voltage reaches threshold. First neuronAxonTerminalSynaptic gapIon channelsDendriteReceiving neuronOutput axon

Signals over time

incoming nerve spike synaptic current receiving-cell voltage firing threshold

Sequence

Step 1 Incoming nerve spike

A brief electrical spike travels along the first neuron’s axon.

Step 2 Transmitter release

The terminal releases neurotransmitter when the spike arrives.

Step 3 Synaptic current

Transmitter opens ion channels in the receiving membrane.

Step 4 Voltage response

Synaptic current changes the receiving neuron’s voltage.

Step 5 New nerve spike

The receiving neuron fires if its voltage reaches threshold.