Hormones and Signaling

Multicellular organisms require robust mechanisms to effectively communicate between distant tissues within their bodies. Such communication is essential for coordinated responses to external cues, such as a flight response after detecting a nearby predator or carrying out complex reproductive behaviors after identifying a potential mate. The nervous system uses neurons to transmit sensed information directly to other cells through axons and nerve terminals, but this approach can only reach a limited number of cells that are directly or indirectly innervated. The endocrine system evolved to provide a mechanism to broadly transmit information across the organism and uses hormones for this purpose.