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Stress and GAS- Hans Selye Selye (1956)– administered noxious agents to rats and he found that they had same physiological response Could be the same.

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Presentation on theme: "Stress and GAS- Hans Selye Selye (1956)– administered noxious agents to rats and he found that they had same physiological response Could be the same."— Presentation transcript:

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2 Stress and GAS- Hans Selye Selye (1956)– administered noxious agents to rats and he found that they had same physiological response Could be the same with humans & stress? Different sources of stress – same non-specific physiological response occurs – which can be harmful Selye (1956) Called this General Adaptation Syndrome (GAS)

3 The transactional model of stress Most popular model for studying stress today – stress as a lack of fit between the perceived demands of a situation and the persons ability to cope In this model any stimulus which produces physical signs of a stress response is a stressor E.g. Exams – some overestimate the demands? may be very stressed and do well Some underestimate the demands, and do badly So there is a cognitive element and there are individual differences in this

4 The bodys response to stressors Two main responses – both involve the adrenal glands Two adrenal glands – just above the kidneys : each one made up from: Adrenal cortex & adrenal medulla: these release different types of hormones into the blood stream, and are controlled by two different pathways which are the hypothalamic-pituitary adrenal cortex (HPAC) pathway and hypothalamic-ANS-Adrenal medulla pathway

5 The hypothalamic-pituitary adrenal cortex pathway (HPAC) Controlled by the hypothalamus and pituitary gland Hypothalamus is a small structure at the base of the brain Pituitary gland master gland as it releases many hormones into the bloodstream When we are confronted with a stressor - it releases ACTH hormone and this travels to the adrenal cortex and triggers the release of corticosteroids – a vital part of the stress response – mobilising energy reserves – heart rate & blood flow The HPAC pathway is activated when higher brain centres evaluate a situation as stressful and instruct the hypothalamus to release the CRH hormone to stimulate the release of ACTH from the pituitary gland

6 Higher Brain Centres (cortex & limbic systems) Hypothalamus BrainstemPituitary gland Adrenal cortex Adrenal medulla Neural control via autonomic nervous system Epinephrine (adrenaline) and Norepinephrine (nor-adrenaline) In bloodstream Corticosteroids In bloodstream Metabolic effects on the body (higher heart rate & blood pressure to get oxygen to muscles) ACTH hormone in bloodstream The red arrows show the hypothalamic-pituitary adrenal cortex (HPAC) pathway Stressor CRH Hormone

7 The hypothalamic- autonomic nervous system (ANS) adrenal medulla pathway The autonomic nervous system (ANS) is a network of nerve pathways running from the lower part of the brain (the brainstem) to the bodys organs. Heart Digestive system Circulatory (blood) system Various glands- including the Adrenal medulla The ANS is controlled by the higher brain structures, especially the hypothalamus

8 Higher Brain Centres (cortex & limbic systems) Hypothalamus BrainstemPituitary gland Adrenal cortex Adrenal medulla Neural control via autonomic nervous system Adrenaline and Noradrenaline in Bloodstream (increases heart Rate & blood pressure) Corticosteroids In bloodstream Metabolic effects on the body ACTH in bloodstream The green arrows show the hypothalamic-ANS-Adrenal medulla pathway Stressor Activates The ANS sympathetic subdivision Via the brainstem CRH Hormone

9 Activating the bodys stress response Selye identified the HPAC & hypothalamic-ANS-adrenal medulla pathways as the main components of the bodys response to stressors He then thought about why they become activated Both systems prepare the body for energy expenditure – normally hypothalamus and ANS does this without of conscious involvement – making sure the body is functioning properly but we also need higher brain centres when things happen in the world which we have to respond to quickly. Cannon (1914) called this the - FIGHT OR FLIGHT RESPONSE

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11 Fight or Flight Response Increase oxygen intake Release stored glucose Divert resources away from digestion Ready to expend energy, either by fighting or by running away

12 Fight or Flight and your Body Sympathetic (Pumps you up) Parasympathetic (chill out) Pupils Lungs Heart Liver Stomach Saliva Activity: fill out this sheet with the effect of stress on these parts of the body

13 Higher Brain Centres (cortex & limbic systems) Hypothalamus BrainstemPituitary gland Adrenal cortex Adrenal medulla Neural control via autonomic nervous system Corticosteroids In bloodstream ACTH in bloodstream Stressor The thick arrows show the hypothalamic-pituitary adrenal cortex (HPAC) Pathway (colour in red) The thin arrows show the hypothalamic-ANS-Adrenal medulla pathway (colour in green) Activity: make your own diagram CRH Hormone Metabolic effects on the body (higher heart rate & blood pressure to get oxygen to muscles) Activates The ANS sympathetic subdivision Via the brainstem Adrenaline and Noradrenaline in Bloodstream (increases heart Rate & blood pressure)

14 Phase 1: Alarm Stress response systems activated Phase 2: Resistance Body copes with stress Phase 3: Exhaustion Stress related illness may develop The three phases of the General Adaptation Syndrome (GAS) (Selye, 1956)

15 The General Adaptation Syndrome (GAS) (Selye, 1956) The GAS has three phases 1 st phase – The alarm phase, the presence of a stressful event is registered – could be a threat from an outside or physical stressor – such as an injury or illness affecting the body - the hypothalamic-pituitary adrenal cortex (HPAC) pathway and hypothalamic-ANS-Adrenal medulla pathway prepare the body for energy expenditure (fight or flight) – nowadays many of the stressors are psychological

16 The General Adaptation Syndrome (GAS) (Selye, 1956) 2 nd phase is resistance – the bodys stress response is fully activated and coping with the stressor, so from the outside things appear to be back under control However, the body enters the 3 rd phase of exhaustion if the stressor is long lasting and chronic. Hormone levels are depleted, and stress related conditions such as raised blood pressure, ulcers, depression and anxiety may develop as stress systems become exhausted

17 Evaluation of GAS Experimental support – first systematic attempt to explain the bodys response to stress based on experimental data – also the first to emphasise the role of the hypothalamic-pituitary adrenal cortex (HPAC) pathway and hypothalamic-ANS-Adrenal medulla pathways Use of non human animals – Research carried out on rats, using physical stressors. Differences between the physiology of rats and humans, so its difficult to generalise his work to humans, however, his later work was done with humans Individual differences- GAS ignores individual differences, e.g. Type A behaviour (Highly driven people who thrive in stressful situations). It assumes that we all respond the same way to stress, but personality and gender can also play role

18 Questions to check your understanding 1) What are the two divisions of the nervous system 2) How does communication occur in the endocrine system? 3) Which is the faster method of communication? The NS or the Endocrine system? 4) What does the Sympathetic and Para-Sympathetic subdivisions of the ANS do? 5) Hormones travel through our……………. 6) The pea sized governor is also known as the ………………… 7) Give a definition of stress 8) What is a stressor? 9) How does the body respond to stress through the hypothalamic-pituitary adrenal cortex (HPAC) pathway 9) How does the body respond to stress through the hypothalamic-ANS- Adrenal medulla pathway 10) What is the fight or flight response? 11) What is the first stage of GAS? – What pathways are activated? 12) What is the second stage of GAS? 13) What is the third stage of GAS?

19 Energy mobilisation Nowdays stress comes from psychological sources such as the workplace/ relationships Physical activity rare in the response to stress – but GAS response preparing us for fight or flight Glucose and fatty acids produced to prepare for fight or flight cant all be re-absorbed into the body if stress is chronic, and the furring up of the cardiovascular system (hypertension & atherosclerosis)

20 Stress and Physical Illness Principle of the biological LOA demonstrated: there is a relationship between our stress response system (which works through and our nervous/endocrine system and is usually activated by psychological stressors) which then has an effect on our immune system causing illness (this is a biological correlate of behavior)

21 Stress and physical illness The immune system is a very complex system of cells and chemicals which protect the body from infection by viruses and bacteria. But during stress all resources are geared to escape, so protection and tissue repair can wait till later Its an excellent survival mechanism – but long term activation can lead to the shutting down of other systems which are also important

22 Walk and talk Using the note-card provided gather as many ideas as you can about the immune system and stress. You need to use the popcorn partner idea- only one fact from each person and it needs to be a new one; you need to exchange with each person in the class. When you have finished your quest for facts write an answer to the following questions How do steroids relate to stress? How does a persistent flow of steroids affect ones physical health?

23 The Immune System Structures and mechanisms that allow the body to resist and fight off infection by: Bacteria Viruses (aka antigens) White blood cells provide mechanisms of immunity (white blood cell) T-LymphocytePhagocyte

24 Non specific immunity - Surround and ingest foreign particles whenever they find them (white blood cell) Phagocyte (white blood cell) T-Lymphocyte Cell-based immunity –produced in the thymus gland they search & destroy foreign cells and cells infected with antigens such as bacteria

25 Immune system very complex & stress- response can affect it directly E.g. high levels of corticosteroids can shrink the thymus gland – preventing the development of T-Lymphocyte cells Long term stress causes long term reductions in immune function (Willis et al. 1987) Diet, exercise, and social support can improve immune function and it will recover if the stressful situation is resolved (Sapolsky, 1994) Suppression of the immune system

26 Stress & Immune Function Cohen & Herbert (1996) Stress associated with increased susceptibility to cold, flu, herpes virus, chickenpox Bartrop et al (1977) Immune suppression followed loss of intimate relationship through death or divorce Levy et al (1989) PPs who scored high on a scale of daily hassles had lower natural killer (immune) cell activity

27 Stress & Immune Function Evidence supports a weak link between stress and immune functioning The relationship is mediated by: Personality & coping style Social support Lifestyle Compared to impact of e.g. age, genes, nutrition stress is relatively unimportant

28 Other effects Stress hormones such as corticosteroids may influence the pituitary gland the master gland (which controls many bodily functions) The pituitary gland controls sexual and reproductive functions – In males, testosterone in males declines in the stress response. In females, the menstrual cycles can be disrupted Growth hormones are also controlled by the pituitary gland – some children suffer from stress dwarfism

29 Evaluation Suppression of immune functioning need not lead to illness and disease, you still need to be exposed to an infectious agent for illness to develop Correlations often small but significant Conclusion: there is a relationship between stress and physical illness, and this may be due to immunosuppression, and can also be explained by Selyes (1956) GAS.

30 Stress stimulates production of steroids. Steroids suppress the immune system Little effect when secretion is intermittent Persistent secretion decreases inflammation (increased blood flow to any injured area resulting in redness and increase in white blood cells Interferes with formation of anti-bodies therefore become susceptible to illnesses

31 Studies relating to stress and lifestyle i.e the effect of the environment on physiological processes In your group write up notes regarding the assigned study. Join another group and share details ensure that you have exchanged with all groups.


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