title: Hormones, neurosecretions, and growth factors as signal molecules for intercellular communication.
abstract: Chemical signals, whether in the form of hormones, neurosecretions (neurotransmitters and neuropeptides), or growth factors and chalones are used to communicate information to cells at all stages of their life cycle. These signals inform the cells when it is time to progress through developmental change, when to change the rates of various activities (e.g. metabolism or contraction), and, in some cases, even when it is time to die. Throughout all of these interactive exchanges, the signal molecule itself carries no intrinsic message of a universal nature. The chemical identity of the signal molecule has meaning only for those cells competent to receive the signal (i.e. does it possess an appropriate receptor?). Moreover, it is the nature of the cell receiving the signal (itself the product of innumerable previous encounters with signals from other cells) that dictates the specific response that a particular signal will evoke. The signal emitted by the communicating cell only informs the target cell that it is time to act in a manner consistent with that signal. The majority of the discussion has been from the perspective of vertebrate organisms. Moreover, of necessity, the discussion has been general and superficial. The primary objective of the preceding discussion has been to underscore major similarities and differences existing among hormones, neurosecretions (neurotransmitters and neuropeptides), and growth factors as information-bearing substances used in communication among vertebrate cells. It should be realized that similar means of communication are employed by multicellular invertebrates, by plants, and even by single-celled organisms such as the protists and bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D002450:Cell Communication; D002468:Cell Physiological Phenomena; D006133:Growth Substances / Q000502:physiology*; D006728:Hormones / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000502:physiology; D018377:Neurotransmitter Agents / Q000502:physiology*
chemical_list: D006133:Growth Substances; D006728:Hormones; D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents