Water Balance

• What is water balance in the body?

  Water balance (osmoregulation) is the control of water levels in the body to maintain a stable internal environment. It ensures that cells do not become too swollen (too much water) or shrivelled (too little water)
• Why does the body need to control water levels?

  Prevents cells from bursting or shrinking due to osmosis.

  • Maintains the right concentration of ions and glucose in the blood.
  • Prevents dehydration, which can cause confusion, fatigue, and organ failure.
• How does the body lose water?

  Urine – The kidneys remove excess water.

  • Sweat – Water is lost through the skin to cool the body.
  • Breathing – Water vapour is lost in exhaled air.
• What role do the kidneys play in water balance?

  • The kidneys filter the blood, removing waste, excess water, and ions.
  • They reabsorb water if the body needs more.
  • Excess water is removed as urine
• What is ADH, and how does it regulate water levels?

  Antidiuretic hormone (ADH) is released by the pituitary gland when water levels are low.

  • It makes the kidneys reabsorb more water, reducing urine volume.
  • This prevents dehydration and keeps blood concentration stable
• How does the body respond to dehydration?

  More ADH is released → Kidneys reabsorb more water → Less urine is produced.

  • Urine becomes dark and concentrated.
  • Blood becomes more concentrated, which can cause headaches, dizziness, and tiredness
• What happens if you drink too much water?

  Less ADH is released → Kidneys remove excess water → More urine is produced.

  • Urine becomes pale and dilute.
  • Too much water can lead to water intoxication, where cells take in excess water and swell, potentially causing brain damage
• How does negative feedback control water balance?

  • Low water levels → More ADH is released → Kidneys reabsorb more water and water levels return to normal.
  • High water levels → Less ADH is released → Kidneys remove excess water and water levels return to normal.