Homeostasis 

Covers control of blood glucose, heart rate and temperature. also discusses neuronal response.

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  • Created by: Orianne
  • Created on: 03-01-13 17:34
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  • Homeostasis
    • the maintenance of the internal environment of the body regardless of the external environment
      • Neuronal Rapid response. Action Potentials all have same size. Frequency indicates size of stimulus
        • Resting potential
          • 3 Na + in.  for every 2K+ out.
            • -70mV
        • generating an action potential
          • Sodium channels open  in response to stimulus. depolarising the membrane as Na+ move into the cell.
            • If enough sodium channels are opened and the membrane reaches the threshold potential of -50mV. an action potential is generated.
              • Threshold potential = opening of voltage sensitive Na+ channels
                • At +40mV sodium channels close. potassium channels opened. membrane repolarises.returns to resting state.
          • Transmission of Action Potential
            • SALATORY  CONDUCTION  result of myelin sheath. faster  than local currents as current is elongated jumps to node of ranvier.
            • LOCAL CURRENTS unmyelinated neurone. sodium ions diffuse away from high region of conc. causes sodium channels to open.
    • Temperature
      • Controlled by thermoregulatory centre in hypothalamus of brain.
        • peripheral temperature receptors detect external temperature.
        • INCREASING TEMPERATURE
          • vasconstriction. less radiated heat lost from skin
          • Liver cells increase rate of metabolism, more heat from respiration which is transferred to blood.
          • Hairs raise to trap a layer of air which insulates the skin and reduces heat loss.
          • increase surface area of body exposed to the sun.
          • move about to generate heat in muscles.
        • DECREASING TEMPERATURE
          • Secrete more sweat onto skin, sweat evaporates using latent heat of vapourisation.
          • Vasodilation. allows more blood to flow through capillaries near to surface of skin. heat is radiated of skin.
          • move into shade. spread out to increase SA for heat loss.
    • Blood glucose concentration
      • Controlled by Alpha and Beta cells of the pancreas.
        • Glucagon increases blood glucose concentration
          • glycogenlysis
          • gluconeogensis
        • Insulin decreases blood glucose concentration.
          • target cells - hepatocytes, muscle cells become more permeable to glucose. glucose is converted to glycogen.
          • Beta cells
      • TYPE 1 DIABTES
        • early onset. Autoimmune disease. B cells are attacked by bodies immune system. More water is excreted due to hight blood sugar. Treated with insulin inje
      • TYPE 2 DIABTES
        • insulin resistance by body cells. B cells begin to los ability to secrete insulin at hight rates, can be causesd by high sugar diet, inactive lifestyle etc. can usually be controlled by diert, weight loss and excercise.
    • Heart rate
      • Controlled by the Medulla Oblongata in the cardiovascular centre of the brain
        • IF TOO LOW  the chemoreceptors and stretch receptors of the vena cava detect.
          • Accelerator nerve sends impulse to SAN, AVN and cardiac muscle. Nor adrenaline is released. INCREASING HEART RATE
        • IF TOO FAST. stretch receptors in carotid sinus and aorta detect.
          • Vagus nerve sends impulse to SAN. Acetylcholine is released. REDUCING HEART RATE.
    • Hormonal, slower long term response. Strength is dependant on amount of hormone released.
      • the maintenance of the internal environment of the body regardless of the external environment
        • Neuronal Rapid response. Action Potentials all have same size. Frequency indicates size of stimulus
          • Resting potential
            • 3 Na + in.  for every 2K+ out.
              • -70mV
          • generating an action potential
            • Sodium channels open  in response to stimulus. depolarising the membrane as Na+ move into the cell.
              • If enough sodium channels are opened and the membrane reaches the threshold potential of -50mV. an action potential is generated.
                • Threshold potential = opening of voltage sensitive Na+ channels
                  • At +40mV sodium channels close. potassium channels opened. membrane repolarises.returns to resting state.
            • Transmission of Action Potential
              • SALATORY  CONDUCTION  result of myelin sheath. faster  than local currents as current is elongated jumps to node of ranvier.
              • LOCAL CURRENTS unmyelinated neurone. sodium ions diffuse away from high region of conc. causes sodium channels to open.
  • Alpha Cells
    • Glucagon increases blood glucose concentration
      • glycogenlysis
      • gluconeogensis

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