Stage 1 of the General Adaptation Syndrome: Alarm
Selye called the first stage of the General Adaptation Syndrome the General Alarm Reaction. This reaction is the result of the biological processes that were described in the section on The Body's Response to stress: Signals are sent to the sympathetic division of the ANS, which increases heart rate, dilates bronchi, inhibits digestion, converts glycogen to glucose etc; meanwhile the hypothalamus also releases CRF, which in turn prompts the release of ACTH from the pituitary which stimulates the secretion of cortisol from the adrenal-cortex.
Stage 2 of the General Adaptation Syndrome: Resistance
If the stressor is not removed the body attempts to adapt to the stress and in the second stage, resistance, it is largely successful; nevertheless, adrenaline and cortisol levels remain high. The consequence of this is that although the body is able to cope, its resources are depleted. If the stress continues for longer the third stage of the syndrome is reached.
Stage 3 of the General Adaptation Syndrome: Exhaustion
Resistance to stress can only be maintained for a limited amount of time. As the body's resources become depleted, the immune system is weakened and health problems develop.