Exercise 9: Renal System Physiology

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Exercise 9
Renal System Physiology

• Hina Rehmani

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Structure and Function of the Kidney

• Wastes produced by metabolism need to be removed
  by the body
• Kidney is made up of about 1 million Nephrons
• Function of the Kidney
• Blood Filtration
• Fluid Processing

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Structure and Function of the Kidney

• Nephrons are microscopic tubules composed of
• Glomerulus
• Renal Tubule
• Glomerulus is a tangled capillary bed
• Filters fluid from blood into the Renal Tubule
• Glomerular Filtration Fluid moves passively out
  of Glomerulus
• Renal Tubule is a long tube
• Processes the filtrate from the Glomerulus
• Tubular Reabsorption Reabsorbs useful substances
  
• Tubular Secretion Move wastes towards
  elimination

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Structure and Function of the Kidney

• The Renal Tubule consists of
• Proximal Convoluted Tubule (PCT)
• Loop of Henle (Nephron Loop)
• Distal Convoluted Tubule (DCT)
• Collecting Duct
• Last part of the collecting tubule in the nephron
• Glomerular capsule surrounds the Glomerulus
• Funnels filtrate into the Renal Tubule
• Renal corpuscle
• Name for the Glomerulus and Glomerular capsule
  collectively

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Structure and Function of the Kidney

• Blood Supply to the Glomerulus
• Afferent Arteriole
• Feed the Glomerular Capillary Bed
• Efferent Arteriole
• Drains the Glomerular Capillary Bed

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Stimulating Glomerular Filtration
Glomerular capsule
Glomerulus
Afferent
Efferent
Collecting Duct
Loop of Henle
DCT
PCT
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Activity 1 Effect of Flow Tube Radius on
Glomerular Filtration

• Procedure Increase the Afferent Arteriole radius
  by 0.05 mm increments
• What happens to the Glomerular Filtration Rate as
  the Afferent radius increases?
• It increases!
• What would happen to the Glomerular Filtration
  Rate if the Efferent radius was increased or
  decreased?
• If increased then Glomerular Filtration Rate
  would decrease
• If decreased then Glomerular Filtration Rate
  would increase

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Activity 2 Effect of Pressure on Glomerular
Filtration

• Procedure Increase the blood pressure supplying
  the Glomerulus by 10 mmHg increments
• What happens to the Glomerular Filtration Rate as
  the blood pressure increases?
• It increases!
• Why does this occur?
• More pressure allows the Glomerulus to push out
  more filtrate

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Activity 3 Combined Effects on Glomerular
Filtration

• Procedure Record a baseline run and compare it
  to a run with the Outflow Valve Closed
• What was the difference between the two runs?
• When the Valve was Closed, there was no
  Glomerular Filtration Rate and no Urine
  Production
• What would happen if the all the collecting ducts
  in the kidney were blocked?
• Pressure would build up
• Ducts would burst/break
• Would kidney function as a whole be affected if
  one nephron was blocked?
• No, because the kidney has about one million
  other nephrons

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Activity 3 continued

• How could the body increase Glomerular Filtration
  Rate in the kidney?
• Dilate the Afferent Arteriole
• Constrict the Efferent Arteriole
• Increase Blood Pressure supplying the Glomerulus

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Review of the Relationships within the Renal
System

• Blood Flow, Glomerular Pressure, Glomerular
  Filtration Rate, and Urine Production are related
• Constricting the Afferent Arteriole causes
• Decrease in Glomerular Pressure
• Decrease in Glomerular Filtration Rate
• Decrease in Urine Production
• Constricting the Efferent Arteriole causes
• Increase in Glomerular Pressure
• Increase in Glomerular Filtration Rate
• Increase in Urine Production

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Stimulating Urine Formation
Glomerular capsule
Glomerulus
Afferent
Loop of Henle
Collecting Duct
Efferent
DCT
PCT
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Activity 4 Role of the Solute Gradient on
Maximum Urine Concentration

• In urine formation, solutes and water move from
  the lumen to the interstitial spaces
• Total solute gradient will effect the movement of
  solute and water to these interstitial spaces
• Antidiuretic Hormone (ADH)
• Increases water permeability in DCT and
  Collecting Duct
• Water flows from high solute conc. into the
  interstitial spaces
• Water is absorbed

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Activity 4 continued

• Procedure Increase the Max. Total Solute
  Concentration of the Gradient by 300 milliosmole
  increments, adding ADH as well
• What happens to the Urine Concentration as Total
  Solute Concentration Gradient (Conc. Grad)
  increases?
• It increases because ADH causes water to move out
  of urine and the more solute there is the more
  concentrated the urine

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Activity 5 Effect of Glucose Carrier Proteins on
Glucose Reabsorption

• There is a limit to the amount of glucose
  reabsorbed because carrier proteins are needed to
  move them to the interstitial fluid
• If glucose carriers are being used, excess
  glucose is eliminated in urine
• Procedure Increase the glucose carriers by
  increments of 100

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Activity 5 continued

• What happened to the glucose concentration in
  urine as the number of glucose carriers
  increased?
• Glucose concentration in the urine decreased
  because the carriers were able to get the glucose
  across
• If there was more glucose than could be
  transported by the available number of glucose
  carrier proteins, what would happen to the urine?
  
• An increased glucose concentration in the urine
• Why do we expect to find glucose in the urine of
  a diabetic person?
• The lack of insulin causes a high glucose
  concentration
• The glucose cant all be absorbed because there
  are only so many glucose carriers

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Activity 6 Effect of Hormones on Urine Formation

• Excess water dilute urine
• Dehydration concentrated urine
• Hormones control urine concentration
• ADH Produced by Hypothalamus and Stored in
  Posterior Pituitary Gland
• Increases water permeability
• Works at DCT and Collecting Duct
• Aldosterone Produced by Adrenal Gland
• Reabsorbs sodium ions and water but loses
  potassium ions
• Works at the DCT

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Activity 6 Continued

• Procedure Compare a baseline run with one when
  Aldosterone is added and one when ADH is added
• How are the results different when Aldosterone is
  added?
• Urine Volume decreases
• Sodium and Water are retained
• Potassium Conc. increases because it is kicked
  out
• How are the results different when ADH is added?
• Urine Concentration increases
• Urine Volume decreases
• Are the effects of Aldosterone and ADH similar or
  antagonistic?
• Similar (Agonists) - both conserve Sodium and
  Water

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