Hormones transduce signals to affect homeostatic mechanisms
المؤلف:
Peter J. Kennelly, Kathleen M. Botham, Owen P. McGuinness, Victor W. Rodwell, P. Anthony Weil
المصدر:
Harpers Illustrated Biochemistry
الجزء والصفحة:
32nd edition.p508-509
2025-11-27
63
The general steps involved in producing a coordinated response to a particular stimulus are illustrated in Figure 1. The stimulus can be a challenge or a threat to the organism, to an organ, or to the integrity of a single cell within that organism. Recognition of the stimulus is the first step in the adaptive response. At the organismic level, this generally involves the nervous system and the special senses (sight, hearing, pain, smell, and touch). At the organ, tissue, or cellular level, recognition involves physicochemical factors such as pH, O2 tension, temperature, nutrient supply, noxious metabolites, and osmolarity. Appropriate recognition of such stimuli results in the release of one or more hormones that will govern generation of the necessary adaptive response. For purposes of this discussion, that is, based on the location of their specific cellular receptors and the type of signals generated. Group I hormones interact with an intracellular receptor and group II hormones with receptor recognition sites located on the extracellular surface of the plasma membrane of target cells. The cytokines, interleukins, and growth factors should also be considered in this latter category. These molecules, of critical importance in homeostatic adaptation, are hormones in the sense that they are produced in specific cells, have the equivalent of autocrine, paracrine, and endocrine actions, bind to cell surface receptors, and activate many of the same signal transduction pathways employed by the more traditional group II hormones.
Table1. The DNA Sequences of Several Hormone Response Elements (HREs)a
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