Humans are open systems who interact, interrelate, and are interdependent with the environment. Throughout the life span, humans strive to achieve optimal well-being through an interactive process between internal an external environments utilizing adaptation. Adaptation is a response to stressors that impact humans' physiological, psychosocial, developmental, cultural, and spiritual dimensions. Health is an individually perceived dynamic state of well-being and is conditioned by the human's ability to adapt to internal and external environmental stressors. Health is characterized by an integrated physiological, psychosocial, developmental, cultural, and spiritual functioning resulting in optimal use of resources to minimize health alternations.
Environment is composed of two components, the internal and external systems.
Interchange occurs between humans' environmental systems. This interchange is impacted by humans' internal environment that consists of physiological, psychosocial, developmental, cultural, and spiritual dimensions. The external environmental system consists of groups of humans united by common familial, geographic, socioeconomic, political, spiritual, and cultural characteristics. Societal groups within the external environment such as families, communities, institutions, and nations are interrelated and interdependent. The viability of any individual or societal group is a consequence of the complementary performance of societal roles within each group in adapting to environmental stressors.