G.A.S. refers to the general adaptation syndrome, which describes the body's response to stress in three stages. Stage 1 involves an initial shock response, followed by activation of the sympathetic nervous system. Stage 2 is resistance, where stress hormones remain high and immune function is compromised. If the stressor persists to Stage 3 of exhaustion, resistance is lowered, leaving the body vulnerable to illness and disease. The G.A.S. model examines how psychological stressors tax the body's defense systems and can impact long-term physiological health if stress is not mitigated.