The Roy Adaptation Model, by Sister Callista Roy, is a conceptual model of nursing that views humans as biopsychosocial adaptive systems that cope with environmental changes through the process of adaptation (Roy and Andrews, 1999; Roy and Zhan, 2006; Tomey and Alligood, 2006). The coping process can be either an adaptive (positive) response or an ineffective (negative) response, and adaptation occurs when the person responds positively to environmental changes (Roy, 1984). The person receives stimuli from both self and the environment and the level of adaptation is determined by the combined effect of focal, residual and contextual stimuli (Roy, 1984). The focal stimulus is “the internal or external stimulus with which the human system is most immediately confronted”; the contextual stimulus “are all other stimuli present in the situation that contribute to the effect of the focal stimulus”; and residual stimuli “are environmental factors within or outside the human system whose effects in the current situation are unclear” (Roy & Andrews, 1999). There are two interrelated subsystems in Roy's model. The primary or control processes consist of the adaptation mechanisms or the regulator and the cognator. The regulator adaptation subsystem provides adaptive mechanisms through adaptive physiological modes involving automatic responses via neural, chemical, and endocrine systems (Andrews and Roy, 1991). The cognative coping subsystem provides coping mechanisms through four cognitive-emotional channels of processing, learning, judgment, and emotion (Andrews & Roy, 1991). The secondary or effector subsystem consists of four adaptive modes: physiological/physical needs, self-concept/group identity, role function, and interdependence (Roy and Andrews, 1999). In other words...... middle of paper ......n & Lange.Mitchell, J. & Bray, G. (1990). Emergency department stress: Guidelines for safeguarding the health and careers of emergency department personnel. Englewood Cliffs, NJ: Prentice Hall. Mitchell, J. and Resnik, H. (1981). Emergency Crisis Response: A Crisis Intervention Guide for Emergency Services Personnel. Bowie, MD: RJ Brady Co. Roy, C. (1984). Introduction to Nursing: An Adaptation Model (2nd ed.). Englewood Cliffs, NJ: Prentice Hall. Roy, C. and Andrews, H. (1999). The Roy Adaptation Model (2nd ed.). Upper Saddle River, NJ: Pearson Education, Inc. Roy, C., & Zhan, L. (2006). Sister Callista Roy's coping model and its applications. In M. E. Parker (Ed.), Nursing theories and practice (pp. 268-280). Philadelphia: FA Davis. Toomey, A. and Alligood, M. (2006). Nursing theorists and their work (6th ed.). St. Louis, Missouri: Mosby Elsevier.