S-Cool Revision Summary.
What is 'stress'?
Stress is a type of alarm reaction, involving heightened mental and bodily states - it is both a psychological and a physiological response to the environment. Your brain produces a stress reaction when you are in a situation that is physically or mentally demanding.
Your body's reaction to stress.
Your brain is on the look out for anything that threatens to upset its equilibrium - if there are serious 'stressors'around, it triggers off an 'alarm reaction'. The alarm reaction prepares your body for action - sometimes known simply as the 'fight or flight reaction'. Stress hormones and the action of the sympathetic nervous system prepare your body for vigorous muscular activity as follows:
- 1. Breathing rate increases.
- 2. Blood flow to skeletal muscles increases.
- 3. Heart rate increases.
- 4. Blood sugar levels increase.
- 5. Blood pressure in arteries increases.
- 6. Pupils dilate.
- 7. Intestinal muscles relax.
So, what if you are not in a situation in which it's OK to suddenly get up and run a four-minute mile round the block?
Well, that's when various unpleasant effects may set in, such as throbbing headaches, irritability, tense neck and shoulders, dried up mouth and butterflies in the stomach. Sound familiar? Most people experience this sort of stress sometimes.
The flow diagram below shows what goes on in the body when the brain detects a potentially harmful 'stressor':.
All the stress hormones circulating in the bloodstream and the neural effects of the sympathetic nervous system combine to create the 'fight-or-flight' response.
The hypothalamus plays a key role in the control of the endocrine system. There is a complex feedback system between the hypothalamus, sympathetic nervous system, the pituitary gland and the secretions of the adrenal glands.
The adrenal glands are found on top of your kidneys - they secrete epinephrine (otherwise known as adrenaline) and other 'stress hormones'. The activity of your adrenal glands is crucial to your mood, energy levels and ability to cope with stress.
In extreme cases of stress your adrenal glands may become enlarged, the spleen and thymus glands may shrink and deep bleeding stomach ulcers may occur. (Not very nice!).
Selye pioneered stress research in the 1950s - he came up with the idea of the general adaptation syndrome.This is a collection of symptoms shown by the body in response to any stress - physical illness such as infection or injury, or stress due to psychological factors. The key thing is that it is 'general' - a non-specific response to any illness.
Here are the three main phases of the 'general adaptation syndrome'.
1. Alarm reaction:.
Shock phase - response to stressor. Hypothalamus, sympathetic nervous system (heart rate and blood pressure increases), pituatory gland and hormones (e.g. adrenaline and corticosteroids) activated.
High level of arousal maintained. Prolonged release of…