Homeostasis

ultrafiltration, selective reabsorbtion etc

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  • Created by: Mia
  • Created on: 21-12-10 20:17

Negative feedback

Factors in blood and tissue fluid must be kept constant:

    • Change affects rate of enzyme-controlled/biochemical reactions
    • Extreme changes denatures proteins
    • Humans maintain constant core body temp between 36-37.8°C
    • Body temp refers to core body temp → limbs may be cooler than 37°C
  • Water potential / avoids osmotic problems → cellular disruption
  • Conc of ions (Na, K, Ca)
  • Homeostasis is achieved by a negative feedback and involves
    • Change in level of an internal factor (change from norm level)
    • Detected by receptors / impulse send to hypothalamus
    • Activates effectors / stimulates corrective mechanism
    • Level of factor returns to norm
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Negative feedback

Controlling the level of water is linked to getting rid of nitrogenous waste so we'll deal with them both together. As mentioned before, nitrogenous waste would be toxic if it accumulated so it must be removed from the body. This is done in number of steps:

  1. Excess proteins (i.e, nitrogenous waste) are broken down into amino acids.
  2.  These then have the nitrogenous part removed as ammonia (see equation 1 below).
  3.  Within the liver, the ammonia is converted into urea (see equation 2 below). This process is called deamination.
  4.  The urea is then transported in the blood to the kidney (where it is extracted and excreted via the bladder).
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