osmoregulation

• What is the term used to describe blood with too low a water potential?


  Hypertonic
• What are some causes of hypertonic blood?


  Loss of water from sweating, not drinking enough water, and lots of ions in food and drink
• What is the corrective mechanism for hypertonic blood?


  More water is reabsorbed by osmosis into the blood from the tubules of the nephrons
• What happens to urine when blood is hypertonic?


  The urine is more concentrated as less water is lost in the urine
• What is the term used to describe blood with too high a water potential?


  Hypotonic
• What are some causes of hypotonic blood?

  Drinking too much water and a lack of ions in the diet
• What is the corrective mechanism for hypotonic blood?

  Less water is reabsorbed by osmosis into the blood from the tubules of the nephrons
• What happens to urine when blood is hypotonic?


  The urine is more dilute and more water is lost in the urine
• Where are osmoreceptors located in the body?


  In the hypothalamus
• What hormone is produced in the hypothalamus related to water potential?

  Antidiuretic hormone (ADH)
• What happens to ADH after it is produced in the hypothalamus?


  It moves to the posterior pituitary gland and is released into the blood
• How does ADH affect the kidneys?


  It increases the permeability of the walls of the collecting duct and distal convoluted tubule to water
• What is the result of increased permeability in the kidneys due to ADH?


  More water leaves the nephron and is reabsorbed into the blood, making urine more concentrated
• Where do ADH receptors bind in the kidneys?


  On target cells in the distal convoluted tubule (DCT) and collecting duct
• What does ADH binding to its receptors activate?

  Adenyl cyclase to make cAMP
• What is the role of aquaporins in the nephron?

  They are channel proteins that allow water to be transported across the membrane
• What happens to the membrane when aquaporins are inserted?


  The membrane becomes more permeable to water, allowing more reabsorption back into the blood