How Specific Are Physiological Regulations?

HOW SPECIFIC ARE PHYSIOLOGICAL REGULATIONS? E. F. ADOLPH, Ph.D.* How does a Hving being automaticauy recognize and adjust the hourly disturbances of each of its many properties and components? When red blood cells have too little glucose in them, they admit glucose. But when their content reaches a norm, they exclude it (i). Will another sugar be accepted in the absence of glucose? Or a fatty acid? How specific is the restitution ofglucose? These questions need to be asked concerning every Hving unit—ceU, tissue, organ, and body. And they need to be asked not only about nutrients, not only about structural chemical constituents, but also about properties like excitability, number ofmitochondria, tensile strength, body temperature, and individual posture. I shaü consider what sort of system an erythrocyte or a man is, that maintains itselflike itself (a phrase of Gasnier and Mayer [2]) hour after hour and year after year. I shall generalize unmercifully from a few examples ofthe maintenances that continuaUy contrive to keep a being alive. We recognize that some influence arising from a disturbance ofthe usual state or norm apparently leads to a correction of the disturbance. How many separate items in that physiological state are differently reacted to? In other words, how many properties are regulated? Does the Hving unit juggle a hundred or a thousand items in its ceaseless insistence on norms? Does it distinguish items the way we do? Is each item provided with a distinctive control? Let me first indicate what I mean by "regulation." Thereafter I shall mention some methodsby which regulations have been successftulystudied and show how the question ofspecificity can be analyzed. Every biologist is intimately acquainted with some specific bodily properties, for he has made them his special study. Many are included in the enormous number * Department ofPhysiology, University ofRochester, Rochester, New York. 55 of details comprised in every treatise on physiology. In this essay I am merely trying to see one general aspect of those details and ask, How specific are the activities that maintain each given property? "Regulation" often remains a hazy term, perhaps because any definition would narrow it toomuch. At the risk ofcramping its use byphysiologists, I suggest that regulation is the act of regularizing what happens. It is the opposite of randomization. A way of conveying what physiologists often think is to say that an animal is compounded ofprocesses but that each ofthese processes is controUed. Movement, chemical transformation, and composition are proceeding at intensities or at rates that are not the greatest ofwhich the tissue is capable. Each activity operates in accordance with influences that determine its amount or that turn it on and off. This was the view ofBernard (3), who did much to show that controls were more intricate in Hving beings than in non-Hving systems. Into the term "regulation" I also inject the notion of smooth running—the control will be consistent with continued operation and will not explode the organism. In researches upon the self-controls of bodily properties, I had to rediscover for myselfwhatBernardhad already stated, thateach regulation depends mostly on some response ofa Hving unit to its own internal state. Hence these researches emphasized those kinds of regulation that result in constancy in the organism (4). Those kinds were termed "homeostatic" by Cannon (5). I have since considered some non-homeostatic regulations, such as those which take the organism away from a steady state or toward a different steady state (6). For instance, in muscular exercise a transition occurs to a second complex ofactivities that is no less regulated than is the resting state to which each component later returns. The term "component" I used to refer to a constituent process or property or substance in an organism. Perhaps we need a more general word, for we are concerned not only with regulation of contraction, of muscle tension, or of water content in a Hving unit but also of all describable characteristics. The term regulatum could refer to any item that can be regulated, which Ithink includes every characteristic or property ofevery living being. So our present task is to find to what degree exemplary regulata are specifically self-managed. When, in studying how an...