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Northburn 100 Miler, For the central nervous system, oxygen toxicity can…

- - - - Low blood sugar levels stimulate the alpha cells in the pancreas to release glucagon into the blood. Cells which absorb this hormone are signalled to convert glucogen (stored glucose) back to glucose to release into the blood.This process is called glycogenolysis.
        
        If the cells exhaust their glucogen supplies then they may begin gluconeogenisis, which is the prodcution of glucose from non-carbohydrate sources.
- - - - Receptors in the hypothalamus detect that the blood volume is too low and the blood is too concentrated
        
        ADH (antidiuretic hormone) is released from the pituitary gland. It helps to maintain water balance by regulating water absorption by the kidneys. More ADH will be released if the blood is more concentrated (ie. more sweating)
        
        ADH travels via the circulatory system to the kidneys and increases the volume of water absorbed by the kidney
        
        The urine output will be low, producing a small volume of concentrated urine. The blood volume will increase until the levels return to normal
  - - - Receptors in the hypothalamus detect the blood volume is too high and the blood is too dilute
        
        ADH secretion from the pituitary gland reduces or stops
        
        This decreases the volume of water absorbed by the kidney
        
        The urine output will be low, producing a high volume of dilute urine. The blood volume will decrease until the levels return to normal
- - - - Oxygen Therapy is utilized to treat high oxygen levels when the body can not (e.g. severe cases). This can involve using an oxygen mask or small tube clipped to the nose which delivers supplemental oxygen
  - - - The kidney (and liver to a smaller extent) release erythropoletin. Erythropoietin is a hormone that has a key role in the production of red blood cells which carry oxygen to the rest of the body.
        
        Erythropoletin stimulates red bone marrow
        
        Enhanced erythropolesis occurs and increases the red blood cell count
        
        The carrying ability of blood increases and oxygen flow returns to normal in the body.
        
        Oxygen Therapy is utilized to treat hypoxemia when the body can not (e.g. severe cases). This can involve using an oxygen mask or small tube clipped to the nose which delivers supplemental oxygen
    - - Severe cases: The carrying ability of the heart significantly decreases due to the lack or low amounts of oxygen. This leads to a decreased RBC amount, Hemoglobin amount and a decreased availability of oxygen for the person.
- - - - In a fully developed body
        
        activates heat-loss centre in hypothalamus
        
        Vasodilation: blood vessels in the skin dilate => heat is lost at the skin surface
        
        Sweating: sweat glands are activated, sweat evaporation loses heat, hairs on the skin flattened => reduced insulating layer => promote heat loss
      - In newborns
        
        Disadvantage
        
        sweating (but sweat glands not fully functional until 4 weeks after birth)
        
        Advantage
        
        have thin skin => blood vessels running near the skin allow heat to be lost easily
  - - - In a fully developed body:
        
        activates heat-promoting centre in hypothalamus
        
        Hormones: thyroid gland releases hormones to increase metabolic rate
        
        Vasoconstriction: Blood vessels in the skin constrict, blood is diverted from the skin => heat is not lost
        
        Muscle: rapid contractions of skeletal muscles cause reflex shivering => expend more energy for heat loss
      - In newborns:
        
        advantage
        
        increased brown fat activity and general metabolic activity => generate heat
        
        disadvantages
        
        have 3 times larger body surface than an adult's => more place for heat to be lost from
        
        have very large head compared to the body (skull's weight about 1/4 total body weight) => high heat loss rate
        
        have very little subcutaneous (white) fat for insulation