Some cells communicate with other cells by secreting chemical mediators.
A chemical mediator is a chemical messenger that acts locally (i.e. on nearby cells). Communication using chemical mediators is similar to communication using hormones – cells release chemicals that bind to specific receptors on target cells to cause a response. But there are a few differences:
1. Chemical mediators are secreted from cells that are all over the body (not just from glands).
2. Their target cells are right next to where the chemical mediator’s produced. This means they stimulate a local response (not a widespread one).