ADH Role

• The main job of the kidneys is to filter the blood and remove all of the waste that we don't want, with urea being the main waste product.
• The kidneys also regulate the levels of useful things like ions and water which we need to keep at the right levels.
• We gain ions like sodium and potassium ions from our diet and need them in the body.
• If the levels of ions or water get too high or too low it can start to damage our cells and cause problems.
• Sweat is a natural way to regulate ions, but the main way we regulate ions is through our kidneys.
• Water regulation is complex as we gain water from the foods and drinks we consume and lose it partly from our skin when we sweat and our lungs when we breathe.
• Most of the water has to be lost from the kidneys in the form of urine.
• The kidneys remove waste products like urea and regulate other substances like ions and water.
• Each of our two kidneys contain around a million tiny tubes called nephrons which perform the filtration and selective reabsorption process.
• Inside the brain, there's a structure called the hypothalamus which detects the concentration of water in the bloodstream and sends a signal to the pituitary gland when the water levels in the body are too low.
• The pituitary gland releases a hormone called ADH into the bloodstream when the water levels in the body are too low, and as the ADH travels around the body it increases permeability of collecting ducts so the tubules to reabsorb more water into the blood, increasing the amount of water in the bloodstream and producing less urine.
• If the level of water in the bloodstream gets too high, the hypothalamus will stop sending signals to the pituitary gland and so it won't release as much ADH so collecting ducts become less permeable and fewer tubules reabsorbing water into the blood, leading to more water staying in the tubules and the kidneys having to produce more urine to get rid of the extra water.
• The process of water regulation is an example of negative feedback to make balance.
• selective reabsoprtion?

  of useful substances such as glucose back into blood via active transport
• filtration?

  small molecules of blood are filtered into tubule (water,glucose,urea). Larger molecules cannot filter into nephron so remain in blood
• function of ADH?

  Increases the permeability of the cell membranes in the collecting duct of nephron so more water is reabsorbed from urine by osmosis.
• what is urea?

  excess amino acids
• reabsoprtion?

  of water from collecting duct into blood by osmosis