osmoregulation

• What is osmosis?

  • Movement of water from a high concentration to a low concentration across a semi-permeable membrane 
• What is osmoregulation?

  • The regulation of water potential 
• What is the structure of the nephron?

  • Glomerulus
  • Renal/bowman's capsule
  • Proximal convoluted tubule
  • Loop of henle
  • Distal convoluted tubule
  • Collecting duct

  
• What is the function of the nephron?

  • Site of osmoregulation in the kidney
  • Controls blood water potential
• What does urine contain?

  • Water
  • Ions
  • Urea
• What does urine not contain?

  • Proteins
  • Blood cells
  • Glucose
• What is urine?

  • the waste product of filtering the blood by the kidneys
• Why are proteins not found in urine?

  • Proteins and blood cells are too big to be filtered out of the blood  
• Why is glucose not found in urine?

  • Glucose is selectively rebasorbed at the Proximal convoluted tubule
• What happens at the glomerulus?

  • Ultrafiltration of blood because of high hydrostatic pressure in afferent arteriole, forcing water and small molecules out the Glomerulus capilarries into the renal/ bowman's capsule
• What happens at the PCT?

  • Selective reabsorption of filtrate such as ions and water but not toxic waste
• What happens at the loop of henle?

  • The descending loop of henle has permeable aquaporins which allows water to leave the filtrate by osmosis
  • The ascending loop of henle has Na+ and Cl¯ which actively trasnport out the filtrate
• What happens at the DCT and collecting duct?

  • Water moves out the distal convoluted tubule and collecting duct to return to blood and remaining filtrate (urine) is sent to the ureter
• What is Selective reabsorption?

  • Sodium moves out PCT lumen and out PCT epithelial cells
  • This makes a concentration gradient
  • Sodium moves back into PCT epithelial cells from the PCT lumen, carrying glucose with it
  • This then diffuses back into the blood cotransporting glucose
• Permeability

  • The more permeable the DCT and collecting duct are, the more glucose can diffuse out and be reabsorbed by the blood
• What does the hypothalamus do?

  • Detects change in water potential by osmoreceptors
  • Synthesises ADH which is sent to the pituitary gland
• What are osmoreceptors?

  • Cells in the hypothalamus that detect a change in water potential
• What is ADH?

  • Anti diuretic hormone
  • Anti-wee-hormone
  • Signals to save water by weeing less
  • Synthesised by hypothalamus
  • Released by pitituary gland
  • Kidney target organ
• What is the target cell of ADH?

  • Complimentary receptors on the distal convoluted tubule and collecting duct inside the kidney nephron
• Why is the decending loop of henle salty?

  • As water leaves by osmosis the concentration of Na+ and Cl¯ ions in the filtrate increase  
• What happens when blood water potential is too high? 

  • Detected by osmoreceptors in the hypothalamus
  • Pituitary gland releases less ADH
  • DCT and collecting duct become less permeable to water
  • Less water is reabsorbed by the blood
  • Urine becomes more dilute 
• What do osmoreceptors do?

  • When the blood water potential is too high they fill with water by osmosis and signal the hypothalamus to produce less ADH
  •  When blood water potential is too low they shrivel and water leaves by osmosis, signalling the hypothalamus to produce more ADH 
• What happens when blood water potential is too low? 

  • Detected by osmoreceptors in hypothalamus
  • Pituitary gland releases more ADH
  • DCT and collecting duct become more permeable to water
  • Water leaves and is reabsorbed by blood