Maintaining internal environments

• Homeostasis is the maintenance of a constant internal environment.
• If body temperature is too high, enzymes denature
• If body temperature is too low, enzymes have less kinetic energy so reactions happen slower. The body stays at 37 degrees.
• If water potential is too high, water enters the cells by osmosis and the cells could burst [lysis]
• If water potential is too low, water leaves the cell by osmosis and cells shrink [crenate]
• If blood glucose levels are too low, there is less glucose for respiration so there is a slower rate, meaning less energy is released.
• If blood glucose levels are too high, there's lower water potential in the blood, so water leaves the cells by osmosis.
• Homeostasis maintains a constant internal environment, so that the cell's metabolic reactions can take place at their optimum rate.
• When your too cold:

  • Body hairs rise, trapping a layer of air close to skin, insulating the body as there are erector muscles in skin contract.
  • Sweat gland stop producing sweat.
  • Blood vessels narrow (vasoconstriction). This reduces blood flow through capillaries, reducing heat loss.
  • Shivering, muscles contract and relax quickly, making your cells respire more quickly, transferring more energy by heating.
• When your too hot:

  • Body hairs lower, preventing insulation around the body.
  • Sweat gland produce sweat, made of water, salt and urea. The water evaporates, reducing your temperature.
  • Blood vessels widen (vasodilation), increasing blood flow, which increases heat loss.
• Blood glucose level too high:

  1. Pancreas detects that blood glucose level is too high and releases insulin into the blood
  2. Blood contains insulin and enters the liver
  3. The insulin causes the liver to store the excess glucose as glycogen
  4. Blood glucose level decreases back to normal
• Blood glucose level to low:

  1. Pancreas detects blood glucose level is too low and releases glucagon into the blood
  2. Glucagon is present in the blood and enters the liver
  3. Glucagon causes the liver the break down glucagon into glucose which is released into the blood
  4. Blood glucose level increases back to normal
• ADH is a hormone that controls how much water is reabsorbed by the collecting duct
• ADH is produced by the pituitary gland
• Water potential of the blood too low:

  1. Osmoreceptor cells lose water by osmosis and shrink
  2. Osmoreceptor cell sends electrical impulse to pituitary gland
  3. Pituitary gland releases ADH into the blood
  4. ADH binds to target cells in the collecting duct
  5. ADH increases the permeability of the collecting duct causing more water to be reabsorbed into the blood.
  6. Smaller volume of concentrated urine produced