Homeostasis and Osmoregulation

• Ways the body loses water


  1. Evaporation of water from the lungs during breathing

  2. Evaporation of sweat from the body

  3. Production of urine by the kidney
• Average volume of water gained by the body each day


  • Drinking 1500 cm³
  • Eating 700 cm³
  • Cell respiration 200 cm³
  • Total = 2400 cm³
• Average volume of water lost by the body each day


  • Urine 1400 cm³
  • Sweat 500 cm³
  • Breath from lungs 400 cm³
  • Faeces 100 cm³
  • Total = 2400 cm³
• Under normal conditions, the volume of water gained balances the volume of water lost
• If there is an increase in temperature


  Then the balance between water gained and lost is disrupted
• Total


  2400 cm³
• Faeces


  100 cm³
• In normal conditions, the volume of water gained balances the volume of water lost but if conditions change (such as an increase in the temperature), then osmoregulation brings the volumes back into balance
• Osmoregulation


  1. Involves the use of

  2. Filter the water that

  3. Load the amount

  4. Reabsorbed
• Conditions that change


  • Very warm weather
  • Vigorous exercise
• Body gains lots of water


  Kidneys produce a more dilute urine with more water
• Body loses lots of water


  Kidneys produce a more concentrated urine with less water
• Water gained by the body each day

  • Drinking 1500 cm³
  • Eating 700 cm³
  • Cell respiration 200 cm³
• Water lost by the body each day

  • Urine 1400 cm³
  • Sweat 500 cm³
  • Breath from lungs 400 cm³
  • Faeces 100 cm³
• Total water gained and lost by the body each day is 2400 cm³
• Antidiuretic Hormone (ADH)


  Hormone that controls the concentration of water in the blood
• ADH regulation of water concentration


  1. Water filtered out of blood is reabsorbed

  2. ADH produced by brain monitors blood water concentration

  3. ADH travels to kidneys

  4. ADH allows more water reabsorption in kidney medulla

  5. Less urine, more concentrated
• ADH regulation on hot day with water loss through sweat


  1. Loss of water through sweat

  2. Concentration of water in blood increases

  3. Brain detects change

  4. More ADH released

  5. More water reabsorbed in kidneys

  6. Less urine, more concentrated
• ADH regulation on hot day with water gain through drinking

  1. Gain of water through drinking

  2. Concentration of water in blood decreases

  3. Brain detects change

  4. Less ADH released

  5. Less water reabsorbed in kidneys

  6. Large volume of dilute urine
• Waste products (such as urea) are removed in the collecting ducts of the kidneys
• Ways the body gains water


  • Respiration
  • Eating
  • Drinking
• Renal artery


  Blood vessel that transports blood to the kidney
• Ureter


  Tube that carries urine from the kidney to the bladder
• Role of kidneys in regulating water in blood

  Osmoregulating the amount of water reabsorbed
• Process involving ADH when losing water through sweating

  1. Loss of water through sweating

  2. Concentration of water in blood increases

  3. Brain detects change

  4. More ADH released

  5. More water reabsorbed in kidneys

  6. Less urine, more concentrated
• Kidney function


  1. Waste not reabsorbed (such as urea) drained into collecting ducts

  2. Collecting ducts pass through medulla and into pelvis of kidney

  3. Collecting ducts empty into ureters for excretion
• Homeostasis


  Maintaining a constant internal environment in the body for the proper functioning of cells and enzymes in response to internal and external change
• Osmoregulation


  Maintaining the water balance at a constant level in the body
• Ways to gain water


  • Drinking liquids
  • In food
• Ways to lose water


  • Evaporation of sweat
  • Breathing out