osmoregulation

• Describe causes for rises in osmotic pressure

  • Little or large volumes of water being ingetsed
  • extent of sweating
  • amount of Salt intake
• What does diuretic mean?

  • Very dilute
• Explain the process of altering the permeability of the collecting duct

  • hypothalamus produces ADH, stored in posterior pituitary gland
  • when WP of blood is too low, hypothalamus causes pituitary gland to release ADH into the blood
  • circulates in the blood and binds to receptors on CD membrane
  • triggers formation of cyclic AMP (cAMP)
  • cAMP causes vesicles in cells lining collecting duct to fuse with cell surface membrane
  • forms aquaporins (protein-based water channels) increase permeability of collecting duct to water
  • water can move out by osmosis and be reabsorbed into blood
  • if WP of blood is too high ADH production is reduced and less aquaporins form
  • controlled by negative feedback
• State the roles of the DCT

  • Na ions actively pumped out of DCT with chloride ions following down electrochemical gradient if body is lacking in salt
  • water can leave DCT to make the urine more concentrated in response to ADH
  • plays a role in balancing the pH of blood
• What is the role of ADH?

  Increases permeability of distal convoluted tubule and collecting duct to water
• What detects/controls negative feedback of ADH production?

  • Osmoreceptors
  • In hypothalamus
  • Sensitive to the conc of inorganic ions in the blood
• what is osmoregulation?

  the process of maintaining or regulating a steady water potential of tissue fluid/blood
• which part of the brain is ADH produced by?

  the hypothalamus, secreted into the posterior pituitary gland where it is stored
• true or false? most water is lost as urine

  TRUE