Answer:
there are 4: paracrine signaling, autocrine signaling, endocrine signaling, and synaptic signaling
Step-by-step explanation:
paracrine:cells that are near one another communicate through the release of chemical messengers
autocrine: a cell signals to itself, releasing a ligand that binds to receptors on its own surface
endocrine:When cells need to transmit signals over long distances, they often use the circulatory system as a distribution network for the messages they send.
synaptic: nerve cells transmit signals. The junction between two nerve cells where signal transmission occurs.