stress booklet

Topics: Immune system, Fight-or-flight response, Nervous system Pages: 14 (3318 words) Published: January 19, 2014
AS Psychology:
Unit 2 PSYA2 (May exam)

Biological Psychology – Stress

Unit 2 Booklet 1 (of 2): Stress as a Bodily Response


First of all we need to answer the question- ‘What is stress?

There is no single definition of stress. Any definition of stress must take into account the internal factors (physiological changes), external factors (the situation itself) and cognitive factors (the person’s perception of the situation and their ability to cope with the demands of the situation).

How does the body respond to stress?

The stress response is important for survival in animals because the physiological changes associated with stress are essential in conditions of fight or flight (i.e. attacking or running away).

The stress response is therefore thought to be:

 An innate, defensive and adaptive response that should promote survival.

A bodily response which enables an animal to react quickly to potentially dangerous stimuli (e.g. when an animal sees a predator, it feels “stressed” and becomes biologically aroused and ready to respond (fight or flight) more quickly to the situation).

 Important because it increases physiological arousal as well as increasing motivation and concentration.

Continual exposure to stressful stimuli, causing prolonged or repeated stress responses may affect health by causing stress-related illness (this will be dealt with later in the booklet…). The Body’s Response to Stressors

There are two parts to the physical (or psychological) stress response system:

1. The Hypothalamic-Pituitary-Adrenal System (HPA)
2. The Sympathetic-Adrenal-Medullary Pathway (SAM)

AO1: The Hypothalamic-Pituitary-Adrenal System (HPA)

Some stressful experiences last for a long time, such as worrying about exams for months beforehand. This is called a chronic stressor and the chronic stress response occurs through the (hypothalamic) pituatary-adrenal system.

When stressed, the hypothalamus sends CRF to stimulate the pituitary gland into releasing ACTH (a stress hormone). The ACTH then stimulates the adrenal cortex (the outer layer of the adrenal gland) into producing hormones known as corticosteroids (e.g. cortisol and corticosterone) which stimulate the liver to release energy.

The function of cortisol is to maintain a steady supply of continued energy. This enables the body to cope with the stressor for maintained periods of time. This means that the body directs its energy towards maintaining energy supplies.

However, the immune system is also suppressed during this process and in the long term, this can lead to immunodeficiency diseases and be damaging for health.

AO1: The Sympathetic-Adrenal-Medullary Pathway (SAM)

Some stress experiences are relatively sudden and brief (like a flash in the pan), such as falling over on an icy path. This is known as an acute stressor and the acute stress response occurs through the sympathomedullary pathway.

Directed by the hypothalamus, the sympathetic branch sends messages, via neurotransmitters, to the adrenal medulla (inner core of the adrenal gland). This results in the release of adrenaline (causing an “adrenaline rush” i.e. feeling scared or thrilled). This “adrenaline rush” makes sure the body is ready for “fight or flight”. The release of adrenaline as well as noradrenaline causes a number of physiological reactions.

The body’s physiological reactions to adrenaline and noradrenaline include an increased heart rate and constricted blood vessels to raise blood pressure. This enables oxygen to be rapidly pumped to the muscles allowing for increased physical activity.

However, continued increases in heart rate and blood pressure can lead to physical damage to blood vessel linings or to muscles of the heart....
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