General Survey ~ Functional Changes in 



the Nervous System Induced by 



Ionizing Radiations 



Paul S. Henshaw 



Division of Biology and Medicine, 

 Atomic Energy Commission, Washington, D. C. 



This session deals with functional alterations in the nervous system that 

 result from exposure to ionizing radiations. In previous sessions, functional 

 changes have been touched on, but more in connection with particular parts 

 of the system. Here, we will devote attention to functional changes involving 

 the nervous system as a whole, and, thereby, performance of the entire 

 organism and even of population groups. 



In this survey I shall consider the efTects of different levels of radiation 

 exposure on the nervous system as an information processing device, and 

 then take into account features which seem to have particular meaning in 

 relation to functional changes. 



Range of Adaptiveness 



Adaptiveness — vigor, stamina or fitness — characterizes nearly all living 

 systems. All ecoentitics, such as cells, tissues, organs, organ systems, organ- 

 isms, and population groups possess an ecoforce which enables them to 

 function and thus to survive, assuming availability of substrate or nutrient 

 materials. 



Figure 1 is drawn as a scale to represent adaptiveness. On such a scale, 

 it is logical to think of three levels of capability: one of maximum perfoiTn- 

 ance, one of normal or usual range performance, and one of minimum 

 performance or the level at which failure occurs. 



With respect to radioneurology and radiobiology, let us consider different 

 kinds of ecoentities, taking first hemojx)ietic tissues, among the most radio- 

 sensitive. We can visualize a level of hemopoietic performance so low that 

 the organism cannot survive, an anemia so severe that death is inevitable. 

 Similarly, we can visualize a level of performance of blood cell output suf- 

 ficient to maintain the normal peripheral blood picture, and one at a much 



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