What are the gaps between nerve cells called?

The gaps between nerve cells are called synapses.

More precisely, a synapse is the communication junction between a neuron and another neuron, muscle cell, or gland cell. In a typical chemical synapse, the tiny physical space between the two cell membranes is called the synaptic cleft, or synaptic gap. In everyday biology questions, however, “synapses” is the standard accepted answer for the connections between nerve cells.

When an electrical signal reaches the end of a neuron, it triggers the release of chemical messengers called neurotransmitters. These molecules cross the synaptic cleft and bind to receptors on the next cell, either stimulating or inhibiting it. The process allows neural networks to process information rather than acting as one continuous wire.

The word synapse was introduced by physiologist Charles Scott Sherrington in 1897. Synapses may be chemical or electrical, and the cleft in a chemical synapse is only about 20 nanometers wide. That narrow space was not clearly resolved until electron microscopy became available in the 1950s.