Hormones

• what is controlled by hormones?

  water reabsorption
• What is theψ of the blood monitored by

  cells called osmoreceptors
• Where are osmoreceptors located

  hypothalamus
• What happens when the ψ of the blood decreases

  Water will move out of the osmoreceptor cells by osmosis

  = causes cells to decrease in volume

  = this sends signal to other cells in hypothalamus , which send a signal to the posterior pituitary gland

  = causes the posterior pituitary gland to release a hormone - ADH
• ADH =


  antidiuretic hormone
• what does ADH do

  Makes the WALLS of the DCT and collecting duct MORE PERMEABLE TO WATER
• ADH makes walls of collecting duct and DCT more permeable to water- what does this mean

  This means more water is reabsorbed from these tubules into the medulla and into the blood by osmosis

  • small amount of concentrated urine produced = less water lost from the body
• What is dehydration


  dehydration= what happens when you lose water

  • so the water content of blood needs to be increased
• How do we lose water -EXAMPLE

  sweating during exercise
• When does blood ADH level rise


  when you're dehydrated
• when does blood adh fall

  when you are hydrated
• What happens to increase the water content of the blood?

  • Water content of blood drops, so its ψ drops
  • This is detected by osmoreceptors in the hypothalamus
  • The posterior pituitary gland is stimulated to release more ADH into the blood
  • More ADH= the DCT and collecting duct become more permeable= more water reabsorbed into blood by osmosis
  • a small amount of highly concentrated urine produced & less water is lost
• What happens when you're hydrated

  • water content of blood rises , so its ψ  rises
  • this is detected by osmoreceptors in the hypothalamus
  • the posterior pituitary gland releases LESS ADH into the blood
  • less ADH = DCT and collecting duct become less permeable = less water reabsorbed into blood by osmosis
  • a large amount of dilute urine is produced and more water lost