human
Can you tell me what a synapse is?
assistant
A synapse is a connection between two neurons, allowing one neuron to send signals to another. It is made up of a gap between the two cells, called the synaptic cleft, and an area on the receiving cell called the postsynaptic density. The neurotransmitter molecules are released from the sending cell into the synaptic cleft, where they bind to receptors on the postsynaptic membrane. This binding causes the postsynaptic membrane to become more permeable, allowing ions such as sodium and potassium to flow in and out of the cell. These ionic changes cause the receiving cell to fire, or "fire back" at the sending cell.