The Physiological Stress Response System – the relationship between mind & body The IB Syllabus Says: We will study: (The effect of psychological stressors (life events, daily hassles & workplace/occupational environment on physiological health) (we will also look at gender & cultural differences and stress management here) We will study: (The interaction between personality/ cognitive style (Type A & Hardy personality & stress related illness)

Background: The Nervous System Consists of billions of nerve cells (neurons) which receive and pass on information within the nervous system Miniscule cells (10 bn in the brain alone!) Spaced out with little gaps called synapses in between them Fire out chemicals to send information across the gaps. Neurotransmitters = the chemical substances that allow communication between nerve cells.

The Nervous System The CNS (Central Nervous System) includes the brain and the spinal cord and contains 90% of the bodies neurons The PNS (Peripheral Nervous System) connects the CNS to the rest of the body – its divided into the Somatic Nervous system (which transmits information about body movements and external environment) and Autonomic Nervous System (which transmits information to and from the internal organs and glands) The endocrine system also works alongside these

Stress A common topic – ‘I’m feeling stressed at the moment’ Stress – may be a reason for high prevalence of anxiety and depression, can also make us more vulnerable to colds and flu Stress – not always negative – from an evolutionary perspective we need stress to survive but stress can become damaging

Key Terms - What is Stress? Two ways to define stress: 1)A state of psychological tension and physiological arousal produced by a stressor (response to a stressor) 2) The lack of fit between the perceived demands of a situation and the person’s ability to cope (This is the transactional model -most popular model today – and we will be studying it in more detail) (if one feels they cannot cope – this leads to stress)

Key Terms - Stressor Something in the environment (such as exams of work pressure, significant life events) that produces a stress response in a person (Selye, 1956)

How does it feel? How did you feel just before your exams last year? Where did you feel it? How were your emotions?

Background: How Does the Body Know it Has to Respond? The body has 2 messenger systems: 1. Nervous System - travels through neurons (or nerve cells) 2. Endocrine System – hormones that travel through the blood

The body’s 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 (H-ANS-AM)

Location of important areas in the bodily response to stress Relay center between CNS and endocrine System Master gland for releasing hormones Controls The bodies organs The two parts of the adrenal gland

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 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 The ACTH travels to the adrenal cortex and triggers the release of cortisol – a vital part of the stress response – mobilising energy reserves – heart rate & blood flow

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

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

The autonomic nervous system is a part of the peripheral nervous system that  functions to regulate the basic visceral (organ) processes needed for the  maintenance of normal bodily functions.

this is done by the ANS without our conscious control The role of the ANS is to maintain normal functioning of the body systems e.g. when you run – the muscles need oxygen and energy, so carbohydrates and fats are converted into sugars and fatty acids in the bloodstream, and our heart rate and blood pressure increases this is done by the ANS without our conscious control To carry out these tasks there are two divisions to the ANS The sympathetic subdivision When activated: the body is Aroused – heart rate and blood pressure increase, fats and carbohydrates are mobilised, digestion slows down ‘Sympathetic arousal’ Gets us ‘pumped up’ Stimulates the fight or flight response The parasympathetic subdivision Heart rate and blood pressure return to normal (decrease), d igestion speeds up – calm and bodily relaxation. Phew – danger over, calms us down again

The divisions of the Autonomic Nervous System ‘pumps up’ ‘calms down’

Adrenaline– well known arousal hormone The adrenal medulla is controlled by the ANS – and activation of the sympathetic branch triggers the release of hormones: Adrenaline– well known arousal hormone Nor-adrenaline– has similar effects they increase heart rate and blood pressure – preparation for ‘fight or flight’ In stressful Situations the hypothalamus activates BOTH the HPAC and hypothalamic-ANS-Adrenal medulla pathways

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

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

Quick quiz……. Give a step by step account of how the HPAC stress response pathway is activated Give a step by step account of how the H-ANS-AM stress response pathway is activated

Question 1 mark scheme Gave full definition of abbreviation 1 mark Mentioned higher brain center evaluating stressor 1 mark Mentions hypothalamus and CRH hormone triggering pituitary gland 1 mark Mentions ACTH hormone triggering Adrenal cortex to release cortisol in bloodstream 1 mark 5. Mentions effects of cortisol on body – increase in heart rate and blood pressure 1 mark Total= 5 marks

Question 2 mark scheme Gave full definition of abbreviation 1 mark Mentioned higher brain center evaluating stressor 1 mark Mentions hypothalamus and Sympathetic subdivision of ANS and neural control via brainstem 1 mark Mentions triggering of adrenal medulla to release adrenaline and nor adrenaline into bloodstream1 mark Mentions effects of adrenaline/nor adrenaline on body – increase in heart rate and blood pressure 1 mark Total= 5 marks

Models of stress Selye (1956)– administered ‘noxious’ agents to rats and he found that they had same physiological response Selye (1956) Called this ‘General Adaptation Syndrome’ (GAS)

Activating the body’s stress response Selye (1956) identified the HPAC & hypothalamic-ANS-adrenal medulla (H-ANS-AM) pathways as the main components of the body’s response to stressors He then thought about why they become activated Both systems prepare the body for energy expenditure Cannon (1914) called this the - ‘FIGHT OR FLIGHT RESPONSE’

‘Fight or flight’ We have evolved from early humans – 10,000 years ago – and are behaviour is still adapted to that environment. E.g. you see a Sabre toothed tiger – if not hunting – run for your life, if hunting attack Same response – higher brain centres in the cortex and limbic system perceiving and evaluating the situation Leads to the HPAC and hypothalamic-ANS-adrenal medulla pathway (H-ANS-AM) activation Then when the emergency is over systems return to normal functioning

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

Fight or Flight Fido enters the classroom looking for trouble, you have 2 choices – run or take him on… For either of these options what would you need? Energy!!!! The Fight or Flight Response = the reaction of the nervous system in response to a stressful situation that produces energy to prepare the body extended and demanding amounts of effort

The Fight or Flight Response An early evolutionary adaptation that is useful in dealing with physical threats Helps us deal with short-term problems that can be solved by fighting or running Unfortunately, many of the threats we face in our society do not fall into these categories… in the modern world, most of the threats in today’s word a psychological, but dealing with these can trigger off the same response in the body as an attacking predator - so we become prepared for physical action with nowhere to go – this can have damaging effects in the long term

The General Adaptation Syndrome (GAS) (Selye, 1956) The GAS has three phases 1st 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 (H-ANS-AM) prepare the body for energy expenditure (fight or flight) – nowadays many of the stressors are psychological

The General Adaptation Syndrome (GAS) (Selye, 1956) 2nd phase is resistance – the body’s stress response is fully activated and coping with the stressor, so from the outside things appear to be back under control The 3rd 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

Stress response systems activated The three phases of the General Adaptation Syndrome (GAS) (Selye, 1956) Phase 1: Alarm Stress response systems activated (HPAC & Hypothalamic ANS pathways) Phase 2: Resistance Body copes with stress Phase 3: Exhaustion Stress related illness may develop Evaluation points?

Evaluation of GAS Experimental support – first systematic attempt to explain the body’s 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

Questions on stress: What's the difference between the central and the peripheral nervous system? Give a definition of stress What is a stressor? How does it feel to be stressed? What are the two main messenger systems of the body? What is the name of the model which explains stress stress that Selye (1956) introduced? What are the names of the main pathways involved in the stress response? When is the HPAC pathway activated? Explain how the HPAC stress response pathway works. What are the two divisions of the ANS? What are the different roles of these two divisions? Explain how the H-ANS-AM pathways works. Complete your own physiology of stress diagram, clearly showing the HPAC and hypothalamic-ANS-Adrenal medulla (H-ANS-AM) pathways and explain them to each other (use colours/etc) What is the name of the researcher who developed this model for stress? When faced with a stressor, the body prepares for energy expenditure, Cannon (1941) called this the........or..............response Why is the fight or flight response activated? What does the fight or flight response do to your body? What are the three phases of the general adaptation syndrome response to stress? Explain each of the GAS stages in detail Make 2 evaluative points that relate to the GAS model of stress?