re the person's external environment.
The interaction of the human system and her or his environment is affected by five sets of variables (Harris, Hermiz, Meininger, and Steinkeler, 1989, pp. 361-387). These variables are associated with physiological characteristics of the person, psychological characteristics of the person, sociocultural characteristics of the person's environment, the developmental characteristics of the person, and the spiritual characteristics of the person.
In Neuman's Health Care Systems Model, the survival structure is the combination of all of the variables applicable to the survival of any human plus the survival variables that are unique to each individual person (Harris, Hermiz, Meininger, and Steinkeler, 1989, pp. 361-387). In the Neuman Health Care System Model, the process of interaction of matter, energy, and information, system input and output, system feedback, negentropy--energy absorption, entropy--energy depletion, and stability function as a single process (H
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