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Concept 44.5: Hormonal circuits link kidney function, water balance, and blood pressure

Concept 44.5: Hormonal circuits link kidney function, water balance, and blood pressure. Mammals control the volume and osmolarity of urine. Fig. 44-18. Fig. 44-19. COLLECTING DUCT LUMEN. INTERSTITIAL FLUID. Osmoreceptors in hypothalamus trigger release of ADH. Thirst. Hypothalamus.

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Concept 44.5: Hormonal circuits link kidney function, water balance, and blood pressure

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  1. Concept 44.5: Hormonal circuits link kidney function, water balance, and blood pressure • Mammals control the volume and osmolarity of urine

  2. Fig. 44-18

  3. Fig. 44-19 COLLECTING DUCT LUMEN INTERSTITIAL FLUID Osmoreceptors in hypothalamus trigger release of ADH. Thirst Hypothalamus COLLECTING DUCT CELL ADH ADH receptor cAMP Drinking reduces blood osmolarity to set point. ADH Second messenger signaling molecule Pituitary gland Increased permeability Storage vesicle Distal tubule Exocytosis Aquaporin water channels H2O H2O reab- sorption helps prevent further osmolarity increase. H2O STIMULUS: Increase in blood osmolarity Collecting duct (b) Homeostasis: Blood osmolarity (300 mOsm/L) (a)

  4. Fig. 44-19a-1 Osmoreceptors in hypothalamus trigger release of ADH. Thirst Hypothalamus ADH Pituitary gland STIMULUS: Increase in blood osmolarity Homeostasis: Blood osmolarity (300 mOsm/L) (a)

  5. Fig. 44-19a-2 Osmoreceptors in hypothalamus trigger release of ADH. Thirst Hypothalamus Drinking reduces blood osmolarity to set point. ADH Pituitary gland Increased permeability Distal tubule H2O reab- sorption helps prevent further osmolarity increase. STIMULUS: Increase in blood osmolarity Collecting duct Homeostasis: Blood osmolarity (300 mOsm/L) (a)

  6. Fig. 44-19b COLLECTING DUCT LUMEN INTERSTITIAL FLUID COLLECTING DUCT CELL ADH ADH receptor cAMP Second messenger signaling molecule Storage vesicle Exocytosis Aquaporin water channels H2O H2O (b)

  7. The Renin-Angiotensin-Aldosterone System • The renin-angiotensin-aldosterone system (RAAS) is part of a complex feedback circuit that functions in homeostasis

  8. Fig. 44-21-1 Distal tubule Renin Juxtaglomerular apparatus (JGA) STIMULUS: Low blood volume or blood pressure Homeostasis: Blood pressure, volume

  9. Fig. 44-21-2 Liver Distal tubule Angiotensinogen Renin Angiotensin I Juxtaglomerular apparatus (JGA) ACE Angiotensin II STIMULUS: Low blood volume or blood pressure Homeostasis: Blood pressure, volume

  10. Fig. 44-21-3 Liver Distal tubule Angiotensinogen Renin Angiotensin I Juxtaglomerular apparatus (JGA) ACE Angiotensin II STIMULUS: Low blood volume or blood pressure Adrenal gland Aldosterone Arteriole constriction Increased Na+ and H2O reab- sorption in distal tubules Homeostasis: Blood pressure, volume

  11. Homeostatic Regulation of the Kidney • ADH and RAAS both increase water reabsorption, but only RAAS will respond to a decrease in blood volume • Another hormone, atrial natriuretic peptide (ANP), opposes the RAAS • ANP is released in response to an increase in blood volume and pressure and inhibits the release of renin

  12. Fig. 44-UN1a Animal Inflow/Outflow Urine Large volume of urine Freshwater fish Does not drink water Salt in H2O in (active trans- port by gills) Urine is less concentrated than body fluids Salt out

  13. Fig. 44-UN1b Animal Inflow/Outflow Urine Bony marine fish Drinks water Small volume of urine H2O out Salt in Urine is slightly less concentrated than body fluids Salt out (active transport by gills)

  14. Fig. 44-UN1c Urine Inflow/Outflow Animal Terrestrial vertebrate Moderate volume of urine Drinks water Salt in (by mouth) Urine is more concentrated than body fluids H2O and salt out

  15. You should now be able to: • Distinguish between the following terms: isoosmotic, hyperosmotic, and hypoosmotic; osmoregulators and osmoconformers; stenohaline and euryhaline animals • Define osmoregulation, excretion, anhydrobiosis • Compare the osmoregulatory challenges of freshwater and marine animals • Describe some of the factors that affect the energetic cost of osmoregulation

  16. Describe and compare the protonephridial, metanephridial, and Malpighian tubule excretory systems • Using a diagram, identify and describe the function of each region of the nephron • Explain how the loop of Henle enhances water conservation • Describe the nervous and hormonal controls involved in the regulation of kidney function

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