Answer
When the body is in homeostasis the conditions of a normal internal environment are maintained. When the body experiences stress the normal physiological conditions of heart rate, blood pressure, hormone levels, glucose consumption etc are reset at levels to counteract the stress. If the stress responses are successful, physiologic conditions slowly return to typical homeostatic levels.
Work Step by Step
The stress response occurs in three stages. In the first stage (fight or flight) the physiological mechanisms of the body rapidly respond under the instruction of nerve impulses from the hypothalamus. As a result heart rate increases, blood pressure rises; blood vessels of skin, and GI tract constrict, while blood vessels of heart, brain, and skeletal muscles dilate. If the stress is not short- lived, a slower response follows the fight or flight response. This response, generated and maintained by hormones, keeps the higher levels of physiologic and metabolic activities working against the stress, for some time. If the stress is eventually removed, the conditions of the internal environment return to homeostasis. If the stress is maintained beyond the capacity of the body to oppose it, exhaustion is the result, and illness and injury ensue.
