AQA psychology AS. Unit 2. Body's response to stress.

The ANS is central to homeostasis, e.g. how humans keep a constant body temperature.

The ANS consists of the sympathetic branch and the parasympathetic branch.

Sympathetic dominance leads to a pattern of bodily arousal, with increases in heart rate and blood pressure. 

Parasympathetic dominance leads to the opposite pattern, one of physiological calm.

The body's response to stress begins with primary or secondary appraisal depending on the processing systems. If the situation is perceived as potentially stressful the hypothalamus at the base of the brain is alerted.

HPA

The hypothalamus detects a stressor and percieves the stimulus as a threat. I then sends a message via neurotransmitters to the pituitary gland. The pituitary gland secretes ACTH which travels in the bloodstream to the adrenal cortex. the adrenal cortex secretes corticosteroids into the bloodstream. The liver then releases stored glucose for energy. This pathway maintains the body on high alert when stress in chronic (longterm).

SAM

Hypothalamus perceives a stressor. The sympathetic branch is stimulated. The SNS stimulates the adrenal medulla to secrete adrenaline and noradrenaline. The body is prepared for fight or flight by increased heart rate, blood pressure and increased muscle tension etc. The pathway is activated under a sudden stressful situation. 

The parasympathetic branch is used to calm the body down and restore it to equilibrium again.

Raised levels of corticosteroids over a long period of time suppress the body's immune system

A major effect of corticosteroids being released is that it increases the levels of glucose and fatty acids in the blood.

Stage 1: ALARM 

A stressor is perceived and levels of stress related hormones surge, heart rate and blood pressure increase, and energy reserves are mobilised. 

Stage 2: RESISTANCE

If the stressor persists the body's response systems maintain their activation.

Stage 3: EXHAUSTION

Long periods of stress eventually exhaust the body's defence systems. This is when stress related illness might occur.

Selye emphasised that the GAS was a common response to all stressors. It is now also thought that stress related illness is not caused by exhaustion of the body's physiological responses but the effect of long lasting high levels of stress hormones.