Fight or Flight Response The Concept of Fight or Flight The concept of physiological changes that occur in the individual was first highlighted by the Fren c h physiologist Claude Bernard in 1878 who described the physiological balance of the internal environment of the individual as the milieu intérieur . I n the first half of the twentieth century, Walter B. Cannon (Walter B. Cannon, 1915) was the first physiologist to introduce the concept of homeostasis for the first time and described the role of the adrenal medulla and the release of adrenaline (also called epinephrine) in the readiness of the individual to face unwelcomed situations. Cannon proposed that the environmental impact on the individual represents a stressful stimulus that provokes the activity of the adrenal medulla and the release of adrenaline. Consequently, adrenaline causes the heart rate to rise, bronchi to dilate, and the blood flow to shift from the skin and digestive system to t