Lecture 4

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Lecture 4
2015-04-21 17:46:25
Lecture 4: Osmoregulation & Excretion
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  1. Osmoregulation
    regulates solute concentrations and balances the gain/loss of water
  2. Excretion
    gets rid of nitrogenous metabolites and other waste products
  3. Osmolarity
    the solute concentration of a solution
  4. Hyperosmotic vs. Hypoosmotic
    • Hyper- higher solute concentration
    • hypo- lower solute concentration
  5. 3 types of nitrogenous wastes
    • ammonia
    • urea
    • uric acid
  6. 4 key functions of excretory systems
    • filtration - filtering of body fluids
    • reabsorption - reclaiming valuable solutes
    • secretion - adding nonessential solutes and wastes from the body fluids to the filtrate
    • excretion - processed filtrate containing nitrogenous wastes released from the body
  7. Overview of excretory process
    blood comes in, gets filtered (filtration), uptake what you need actively (reabsorption), dump things that were not filtered but you want to get rid of (secretion), then get rid of waste from body (excretion)
  8. The two types of nephrons
    • cortical- reach only a short distance into the medulla
    • juxtamedullary- goes deep into the renal medulla
  9. What is the advantage of the juxtamedullary nephron?
    key feature in preserving water and not losing too much
  10. Structure of the kidney
    • renal cortex- top layer
    • renal medulla- inner layer
  11. ____ produces urine, ______ brings urine to _______, which stores urine temporarily, ______ leads urine to the outside
    • kidney
    • ureter
    • urinary bladder
    • urethra
  12. What does the glomerulus (bowman’s capsule) do?
    filters blood
  13. What does the filtrate contain?
    salts, glucose, amino acids, vitamins, nitrogenous wastes, and other small molecules
  14. What happens in the proximal tube?
    • reabsorption of water and nutrients
    • toxic materials are actively secreted into the filtrate
  15. What happens in the descending limb of the loop of henle?
    • as filtrate flows, solutes become more concentrated due to water leaving the tubules by osmosis
    • water is flows out of the filtrate to be in equilibrium with the environment
  16. What happens in the ascending limb of the loop of henle?
    • salt, but not water is able to defuse from the tubule into the interstitial fluid
    • so the filtrate becomes more dilute as it travels back up
    • NaCl is first pumped out passively, then actively
  17. What happens in the distal tube?
    • regulates K+ and NaCl concentrations of body fluids
    • controlled movement of ions contributes to pH regulation
  18. What happens in the collecting duct?
    • carries filtrate through the medulla to the renal pelis
    • water is lost again because environment becomes more concentrated the further down you go
  19. If body has a shorter collecting duct, urine would be
    more diluted because it cannot go through the gradient all the way
  20. How is osmolarity controlled?
    • osmolarity increases
    • hypothalamus senses that
    • posterior pituitary secretes hormone ADH, which travels to collecting duct
    • makes you drink more water and increases ability of collecting duct to reclaim water as it passes through gradient
  21. What does Antidiuretic Hormone do?
    • makes the collecting duct epithelium more permeable to water
    • helps conserve water
  22. Malfunctioning of the ADH-aquaporin system results in
    diabetes insipidus
  23. What is diabetes insipidus
    any abnormal condition characterized by the secretion and excretion of excessive amounts of urine
  24. Mutation in ADH production causes
    severe hydration and results in diabetes insipidus
  25. When is the Renin-Angiotensin-Aldosteron System used?
    when you don’t have a lot of blood or have a high concentration of solutes
  26. Describe the Renin-Angiotensin-Aldosteron System (RAAS)
    • Normal blood pressure/volume
    • Blood pressure/volume drops (injury, blood loss, dehydration)
    • A part in the nephron called juxtaglomerular apparatus (JGA), senses that you don’t have enough blood
    • Triggers a response, produces renin (because of drop in pressure or blood volume)
    • Renin meets angiotensinogen (produced by the liver, does nothing by itself)
    • Renin + Angiotensinogen = Angiotensinogen 1
    • Angiotensinogen 1 taken by enzyme ACE, produces Angiotensinogen 2
    • Angiotensinogen 2 signals adrenal gland to produce aldosterone to increase blood volume
    • More Na+ and H2O are reabsorbed in distal tubes, increasing blood volume
    • Also tells arterioles to constrict, because low blood volume = lower pressure, so arterioles constrict to keep pressure up
  27. What is the role of Angiotensinogen 2?
    • signals adrenal gland to produce aldosterone to increase blood volume
    • tells arterioles to constrict in order to keep the pressure up
  28. Why are some patients treated with ACE inhibitors?
    • because they have hypertension
    • by killing Angiotensinogen 2, blood pressure is decreases because less arterioles will be constricting
  29. What happens when kidneys don’t filter? (3)
    • poor regulation of solutes in blood
    • compromised fluid balance
    • accumulation of toxic waste
  30. What are aquaporins?
    Channels in the membrane that allow water to pass through easily
  31. how does ADH affect aquaporins?
    ADH increases the number of aquaporin proteins in the membrane of collecting duct cells