Body's response to stress; The pathways

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  • Created by: alexandra
  • Created on: 31-05-13 15:22
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  • Body's Response To Stress
    • What is stress?
      • The response that occurs when we think we can't cope with pressures from our environment.
    • The hypothalamus - the control system for most of the body's hormonal systems.
      • The evaluation of whether something is a stressor, occurs in the cerebral cortex.
        • When there's a stressor in the environment these higher areas of the brain send a signal to the hypothamulus which activates one of two pathways.
    • The symphato-medullary pathway (SMP)
      • Initial shock response -> hypo-thalamus triggers activity in the sympathetic branch of the autonomic nervous system - which is a branch of the peripheral nervous system.
        • The sympathetic branch becomes more active when body is stressed and using energy.
          • It stimulates the adrenal medulla within the adrenal glands, which releases adrenaline and noradrenaline into the bloodstream.
            • BP and heart rate increase. Digestion stops. Pupils dilate. Breathing rate increases so more oxygen can be send to the muscles.
              • This prepares the body for the 'fight or flight' system.
                • The para-sympathetic nervous system
                  • Relaxes the body once the stressor has passed.
                    • Slows down the heart beat, Digestion begins again, reduces blood pressure etc.
                      • Known as the body's 'rest and digest' system.
                  • It is a branch of the ANS (autonomic nervous system)
      • Deals with ACUTE STRESS. (Stress that is short-term). It is FAST acting and involves electrical activity.
    • The pituitary-adrenal system (also knows as the HPA - hypothalamic-pituitary-adrenal axis)
      • Deals with CHRONIC STRESS. (Stress that is long term). It is a chemical based system. Not as fast as the SNP.
        • Because the stress is long term, the sympatho-medullary pathway will start using all the body's resources so this second system produces a countershock response - supplies the body with more fuel.
      • 1) The hypothalamus triggers the release of CRF (corticotropin-releasing factor)
        • 2) CRF stimulates the anterior pituitary gland. And this releases a hormone called ACTH (adreno-corticotropin hormone)
          • 3) ATCH stimulates the adrenal cortex.
            • 4) The adrenal cortex release corti-costeroids which give us energy by converting fat and protein.
              • This energy is needed to replace that used up by the body's initial reaction the the stress.


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