Physiological responses
How does the body react in stressful situations?
The body’s stress response process:
- The perception
The brain detects danger: when the brain (mainly the amygdala) detects danger or stress, it sends a signal to the hypothalamus, a central regulatory centre in the brain.
- Hormonal activation
Secretion of adrenaline and noradrenaline: The hypothalamus activates the sympathetic nervous system, which stimulates the adrenal medulla (the inner part of the adrenal gland) to release adrenaline and noradrenaline.
Cortisol release: the hypothalamus stimulates the adrenal cortex through the pituitary gland to produce cortisol. This hormone helps the body cope with stress in the long term.
- Physiological changes:
Heart and vascular system
Increase in heart rate and blood pressure: adrenaline and noradrenaline cause the heart to beat faster and blood pressure to rise to get more blood to the muscles and vital organs.
Blood vessel constriction: blood vessels constrict in some areas, such as the skin, while in other places, such as the muscles, they dilate to optimise oxygen and nutrient supply.
Respiratory system:
Faster Breathing: Breathing speeds up to get more oxygen into the bloodstream, which supports increased muscle activity.
Material exchange
Glucose release: cortisol and adrenaline increase blood glucose levels by releasing more glucose from the liver, which provides immediate energy for the muscles.
Muscle tension
Muscle activation: muscles tense up, ready to act, to react quickly to danger.
Sensory sharpening
Heightened perception: adrenaline and noradrenaline sharpen the senses, especially vision and hearing, to better perceive the dangers around you.
Digestion slowdown
Saving energy: the digestive system slows down as the body saves energy and focuses it on vital organs and muscles.
Immune system
Reducing inflammation: in the short term, cortisol reduces inflammation, but in the long term it can also suppress the immune system.
- Mental and emotional effects:
Increased alertness: the brain is ready to make quick decisions, which improves reaction time and survival chances.
Emotional tension: adrenaline and cortisol increase anxiety and tension, which can be helpful in the short term but exhausting in the long term.
Post-stress phase:
Activation of the parasympathetic nervous system: once the threat has passed, the parasympathetic nervous system starts to work to calm the body, slowing the heartbeat, lowering blood pressure and restoring normal digestion and other functions.
