Renal Flashcards by Emily Caruso

Where does the largest amount of reabsorption occur?

PCT (70%) then TAL (20-25%)

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What do meat eaters secrete?

H+

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What do vegetarians secrete?

bicarb

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What is the equation for excretion?

Excreted = Filtered - Reabsorbed + Secreted

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The beating of the heart creates a hydrostatic pressure within the glomerular capillaries

GBHP

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What is the value of GBHP?

45mmHg

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Does GBHP promote filtration or reabsorption?

Filtration

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Is GBHP higher or lower than in the systemic circulation and why?

higher (~30) because it gets more BF

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Due to the volume constrictions of Bowman’s space, a small “back” pressure can be generated

CHP=capsular hydrostatic pressure

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What is the value of CHP?

10mmHg

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Is CHP higher or lower than in the systemic circulation and why?

Higher (0-1) we are in a much smaller space with only 1 exit point

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Does CHP promote filtration or reabsorption?

reabsorption

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The proteins that are retained within the glomerular capillaries create an osmotic pressure.

BCOP

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What is the value of BCOP?

27mmHg

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Does BCOP promote filtration or reabsorption?

reabsorption

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Is BCOP higher or lower than in the systemic circulation and why?

Higher (18) proteins are more concentrated

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This pressure is 0 mmHg because very few proteins should escape into Bowman’s space (proteins in the urine is a bad thing)

COP = Capsular osmotic pressure

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What is the Net Filtration Pressure at the Glomerulus?

8mmHg

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Amount of filtrate formed in all the renal corpuscles of both kidneys each minute

GFR

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Occurs when stretching triggers contraction of SM cells in afferent arterioles

Myogenic mechanism

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Does the Myogenic mechanism increase or decrease GFR?

decrease

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An analysis of the amount of solute being presented to the tubule for reabsorption or excretion

Filtered Load

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Filtered load =

GFR x Psolute (1/5)

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A process in which the nephron monitors the concentrations of Na and Cl ions arriving at the junction of the TAL and the DCT

Tubuloglomerular Feedback

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In Tubuloglomerular Feedback an increase in GFR is sensed by the macula dense cells of JGA detecting an increase in delivery of Na and/or Cl, Macula dense cells send a signal to the JG cells that causes them to ....

release less NO --> afferent arteriole constricts --> decrease in GFR

What is the outcome of SNS-NE constricting mainly the afferent arteriole?

Decreases RPF and GFR

What is the outcome of Angiotensin II constricting both afferent and efferent arterioles?

Decreases RPF and GFR but less than RPF

What is the outcome of Prostaglandins dilating afferent and efferent arterioles?

increases RPF, GFR may not change, may go up through dose-dependence

What is the outcome of ANP dilating afferent arterioles and constricts efferent arterioles?

Slightly increases RPF, increases GFR

Where are the macula dense cells located?

junction of TAL and DCT

What cells detect the arriving levels of sodium and chloride?

macula densa cells

What are juxtaglomerular cells?

contractile cells located in the afferent arteriole

What is the clearance equation?

C(inulin) = [U(inulin) x v] / P(inulin) units = mL/min

What is the clearance of PAH used to measure?

RPF - the amount of fluid arriving at the kidneys in a period of time.

What is equation to determine RBF?

C(pah) / (1-hematocrit)

What is the equation to determine Filtration Fraction?

FF=GFR/RPF | FF = Cinulin (or creatinine)/Cpah

What fraction of RPF normally filters into Bowman's space?

1/5 = 20%

Where are the primary spots in the nephron for secretion to occur?

1. DCT 2. CD

Where in the PCT is there an abundant reabsorption of the anion bicarbonate?

Early PCT

Where in the PCT is there an abundant reabsorption of the anion Chloride?

Late PCT

What is the symport transporter on the apical side in the early PCT?

SGLT - moving glucose and Na+ into the cell

How is glucose in the Early PCT transported into the blood across the basolateral membrane?

facilitated diffusion using GLUT

What is the antiport transporter on the apical side in the early PCT?

Na-H exchanger via SAT, H+ is secreted and bicarb is reabsorbed

How does the reabsorption of Cl- in the Late PCT occur?

anion shuttle in the apical membrane (anions = glutamate, phosphate, formate)

A process by which an increase in filtration leads to an increase in the reabsorption, and water and solute balance is maintained?

Glomerulotubular Balance

What type of transport is located on the apical membrane in the TAL?

Na+/K+/2 Cl- symporter (NKCC)

How are K+ and Cl- reabsorbed in the basolateral membrane of the TAL?

through leak channels

A drug called Furosemide inhibits what?

NKCC in the TAL

What type of substances are secreted in the nephron?

organic acids (uric acid), H+, any ions in excess, K+, creatinine

Where is ADH released from?

posterior pituitary gland

What is the water permeability of the glomerulus through the descending loop of Henle?

permeable

What is the water permeability of the TAL through Early DCT?

always impermeable

What is the water permeability of the Late DCT and CD?

impermeable to water unless ADH is present

The release of ADH is controlled by cells in the hypothalamus called?

osmoreceptors

Baroreceptors in the .... can also influence the release of ADH from the pituitary.

carotid sinus and aortic arch

What stimuli cause osmoreceptors to increase their generation of APs?

[ECF] becomes high = dehydration --> cell shrinks

What is the effect on ADH of the osmoreceptors increasing their firing rate of APs?

increases the release of ADH

What stimuli cause baroreceptors to increase their generation of APs?

increase in BP --> baroreceptors stretch

What is the effect on ADH of the baroreceptors increasing their firing rate of APs?

inhibits the release of ADH

Which has a larger effect on ADH, osmoreceptors or baroreceptors?

osmoreceptors

What type of receptors does ADH bind to in the Late DCT and CD?

V2 receptors

Binding of ADH to V2 receptors results in what?

insertion of aquaporin-2 channels into the apical membrane

What is ADH's effect on NKCC transporters?

increases their activity in the TAL

When ADH is high how does it affect urine osomolatlity in the Late PCT?

it has no effect still 300mOsm/L

When ADH is high how does it affect urine osomolatlity in the End of the TAL?

increases the NKCC transporters creating a more hypotonic urine (120 --> 100mOsm/L)

When ADH is high how does it affect urine osomolatlity in the Early (cortical) CD?

water is reabsorbed and urine osmolality increases to equilibrate with the interstitial fluid

When ADH is high how does it affect urine osomolatlity in the Later (medullary) CD?

Insertion of ureaporins causes urea to diffuse into the interstitial fluid (1200mOsm/L)

Where is the hormone Aldosterone produced?

Adrenal gland

The liver continuously produces ... which travels through the circulation.

inactive angiotensinogen

If the kidney detects low Na+ levels the JG cells produce what enzyme?

renin

What is the action of Renin?

angiotensinogen --> angiotensin I

What converts Angiotensin I --> Angiotensin II in the blood.

ACE

What nephron segment(s) are in the renal cortex?

PCT and Late DCT

What nephron segment is the main site of glomerulotubular balance?

PCT

What nephron segment is the main site of tubulogolmerular feedback?

TAL

What are the 3 actions of ANP in the nephron?

1. relaxes afferent arteriole 2. constricts efferent arteriole 3. inhibits Na/K pump in late DCT and CD increases GFR and decreases Na reabsorption

How does the class of diuretic that increases GFR influence urine output?

mild increase

How does the class of diuretic that inhibit ADH release influence urine output?

potent increase

How does the class of diuretic that are osmotic or renal-transport inhibiting substances influence urine output?

potent increase

What is a disease state in which an osmotic diuresis occurs?

Diabetes Mellitus

Where would Carbonic Anhydrase Inhibitors be most effective in the nephron?

PCT - inhibit reabsorption of bicarb

Where would Loop Diuretics be most effective in the nephron?

TAL - interrupts counter-current multiplier system

Where would Thiazide-type Diuretics be most effective in the nephron?

DCT - inhibit Na-Cl transporter

Where would Aldosterone Antagonists be most effective in the nephron?

CD - K+ saving