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  • Homeostasis
    • What is homeostasis?
      • Maintenance of a constant internal environment.
        • It involves control systems that keep your internal environment roughly constant. This is vital for cells to function normally and stop them being damaged.
          • It's important to maintain the right core body temperature because temperature affects enzyme activity and enzymes control the rate of metabolic reactions.
      • Temperature
        • The rate of metabolic reactions increases when the temperature increases.
          • More heat means more kinetic energy, so molecules move faster.
            • This makes the substrate molecules more likely to collide with the enzymes' active sites. The energy of these collisions also increases, which means each collision is more likely to result in a reaction.
              • BUT if the temperature gets too high the reaction essentially stops. The rise in temperature makes the enzyme's molecules vibrate more.
                • If the temperature goes above a certain level, this vibration breaks some of the hydrogen bonds that hold the enzyme in its 3D shape.
                  • The active site changes shape and the enzyme and substrate no longer fit together. At this point, the enzyme is denatured- no longer functions as a catalyst.
                    • If body temperature is too low enzyme activity is reduced, slowing the rate of metabolic reactions. The highest rate of metabolic reactions is their optimum temperature about 37 degrees.
    • Negative Feedback
      • Homeostatic systems involve receptors, a communication system and effectors.
        • Receptors detect when a level is too high or too low and the informations communicated via the nervous system or the hormonal system to effectors.
          • The effectors respond to counteract the change- bringing level back to normal. The mechanism that restores the level to normal is called a negative feedback mechanism.
            • Negative feedback keeps things around the normal level.
              • Negative feedback only works within certain limits though- if the change is too big then the effectors may not be able to counteract.
    • Positive Feedback
      • Some changes trigger a positive feedback mechanism, which amplifies the change.
        • The effectors respond to further increase the level away from the normal level.
          • The mechanism that amplifies a change away from the normal level is called positive feedback mechanism.
            • Positive feedback isn't involved in homeostasis because it doesn't keep your internal environment constant. It is used to rapidly activate processes in the body.


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