Osmoregulation

• What is osmoregulation?

  Controlling water potential of the blood.
• What is blood with too low water potential described as?

  Hypertonic
• What is low water potential of the blood caused by?

  Loss of water by sweating

  Not drinking enough water

  Lots of ions(salts)in food or drink
• What can happen to cells as a result of low water potential in blood?

  Too much water will leave the cells and move into the blood by osmosis.

  Cells will shrivel(crenation)
• What is the corrective mechanism for low WP in blood?

  More water reabsorbed into the blood by osmosis from the tubules of the nephron.

  Urine is more concentrated as less water is lost in urine.
• What is blood with too high WP described as?

  Hypotonic
• What is high WP in blood caused by?

  Drinking too much water

  Lack of ions(salts) in food
• What will happen to cells as a result of high WP in blood?

  Too much water will move from the blood into the cells by osmosis. Cells will burst(lyse)
• What is the corrective mechanism for high WP in blood?

  Less water is reabsorbed by osmosis into the blood from the tubules of the nephrons.

  Urine is more dilute and more water is lost in urine.
• What are changes in the water potential of the blood detected by?

  Osmoreceptors.
• Where are osmoreceptors found?

  Hypothalamus
• Where is antidiuretic hormone (ADH) produced, and then released from?

  Produced in hypothalamus

  Released from prosterior prituatary gland
• Where and how does the ADH travel after being released?

  Travels in the blood to the kidney.
• How is a high WP of blood detected, and what does this stimulate?

  Water enters osmoreceptors by osmosis.

  This stimulates hypothalamus to produce less ADH
• How is low WP of blood detected, and what does this stimulate?

  Water leaves the osmoreceptors by osmosis causing them to shrivel.

  This stimulates the hypothalamus to produce more ADH.
• What does ADH cause when it reaches the kidney?

  An increase in the permeability of the walls of the DCT and collecting duct to water.

  This causes more water to leave the nephron and be reabsorbed by the blood.
• What do ADH bind to?

  Receptors on the cell membranes of the DCT and collecting duct.
• What does this binding of ADH to these receptors activate?

  Activates the enzyme phophorylase
• What does the enzyme phosphorylase cause?

  Causes vesicles containing aquaporins to fuse with the cell membrane, the aquaporins embed.
• What are aquaporins?

  Protein channels for water to pass through.