Final answer:
Animal cells use extracellular signal molecules called ligands to communicate with one another. These ligands bind to receptors on target cells, initiating a chain of events that leads to a cellular response. Cell communication can happen over short distances or long distances through the bloodstream.
Step-by-step explanation:
Animal cells use extracellular signal molecules to communicate with one another in various ways. These molecules, called ligands, are secreted by signaling cells and bind to specific receptors on target cells. This binding initiates a chain of events within the target cell, leading to a cellular response. There are several types of cell communication, including paracrine signaling (short-range communication), endocrine signaling (long-range communication through the bloodstream), autocrine signaling (self-signaling), and direct signaling through gap junctions.