The essence of multicellularity is the coordinated interaction of the various kinds of cells that make up the body.
Cells communicate with each other by chemical signals.
Autocrine signaling can occur solely within the cytoplasm of the cell or by a secreted chemical interacting with receptors on the surface of the same cell paracrine - chemical signals that diffuse into the area and interact with receptors on nearby cells. The release of neurotransmitters at synapses in the nervous system. This page will examine the properties of endocrine signaling. These receptors are transmembrane proteins . The receptors are transmembrane proteins.