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Hum Physiology II > Tubular transport, lect 4 > Flashcards

Tubular transport, lect 4 Flashcards

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1
Q

give equation for filtered load

A

FLx = GFR x Px

  • Px = plasma concentration of X
  • equation gives the amount of material in glomerular filtrate
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2
Q

give equation for excretion rate (mg/min)

A
  • amount of material lost in urine
  • ER = (Ux)(V)
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3
Q

Give equation for transport rates

A
  • amount of material added to (secreted) or removed (reabsorbed) from glomerular filtrate
  • Tx = FL - ER
    • ER: excretion rate
    • if positive: then some material was removed from filtrate by reabsorption
    • if negative: then some material was added to the filtrate by secretion
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4
Q

name the two routes of reabsorption

A
  • paracellular (Between cells)
    • “leaky” epithelium
  • transcellular
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5
Q

transcellular reabsorption must cross what two barriers

A
  • luminal (apical) membrane
  • basolateral membrane
    • diffusion through interstitial fluid and capillary wall is fast
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6
Q

reabsorption of amino acids, glucose, lactate, citrate, phosphate etc. is done via what mechanism

A
  • secondary active transport
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7
Q

2/3 of water is passively reabsorbed and 2/3 of sodium is actively reabsorbed where in the nephron

A

proximal tubule

  • 2/3 is reabsorbed no matter how dehydrated a person is
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8
Q

sodium reabsorption in the distal tubule and collecting tubule is subjected to control by what

A

aldosterone

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9
Q

water reabsorption in the distal and collecting tubule is regulated by

A

ADH

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10
Q

fluid reabsorption is achieved through what mechanism?

A

a high oncotic pressure in the peritubular capillary

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11
Q

sodium enters proximal tubule cells via what transport system

A

via cotransport with organics and by Na+-H+ antiport (NHE)

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12
Q

sodium leaves the proximal tubule cell to enter interstitium via what transport mechanism

A
  • Na+K+ ATPase or via cotransport with HCO3-
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13
Q

sodium potassium ATPase is always located on what side of proximal tubule cell

A

interstitium side (near blood capillary)

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14
Q

angiotensin II influence on Na+ reabsorption in the proximal tubule

A
  • stimulates Na+H+ exchange (NHE) across apical membrane
  • increases Na+ reabsorption and H+ secretion
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15
Q

sympathetic nerve activity on Na+ reabsorption in the proximal tubule

A

stimulates Na+ reabsorption

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16
Q

parathyroid hormone influence on Na+ reabsorption in the proximal tubule

A
  • inhibits Na+-phosphate cotransport
  • increases urinary excretion of phospate
  • relates to calcium homeostasis; parathyroid hormone released when calcium levels in blood are low and function is break down bone to release calcium; bone releases ca2+ and phosphate but don’t want them to meet in blood so parathyroid inhibits reabsorption of phosphate
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17
Q

tubular fluid to plasma concentration (TF/P) = 1

what does this mean

Study These Flashcards
A

reabsorption has been exactly proportional to the reabsorption of water

18
Q

does osmolarity change in tubular fluid to plasma concentration ratio in proximal tubule

Study These Flashcards
A

osmolarity DOES not change

19
Q

tubular fluid to plasma concentration (TF/P) < 1

what does this mean

Study These Flashcards
A

reabsorption of the substance has occurred to a greater extent than water

20
Q

tubular fluid to plasma concentration (TF/P) > 1

what does this mean

Study These Flashcards
A

reabsorption of the substance has been less than water OR there has been net secretion of the substance

21
Q

how is tubular fluid to plasma concentration of inulin (TF/P) used

Study These Flashcards
A

used as marker

  • since inulin is only filtered, its concentration in the tube is solely determined by the movement of water
22
Q

what is tubular maximum (TM)

Study These Flashcards
A

the maximal rate at which renal transport systems can transport a particular solute

  • maximum rate (mg/min) of a solute that can be transported
23
Q

What is tubular maximum (TM) due to

Study These Flashcards
A

due to saturation of membrane transport proteins

24
Q

below tubular maximum (TM), all of the filtered load is

25
above tubular maximum (TM), all of the filtered load is
excreted
26
tubular maxima are found primarily in which portion of the nephron
proximal tubule
27
how do you find transport maximum on blood X concentration vs rate (mg/min) graph
rate when reabsorption levels off
28
In a blood X concentration vs rate (mg/min) graph, what does decreasing the GFR do to the threshold
decreasing GFR increasing threshold * threshold (x axis point when reabsorption line breaks off from filtered (GFR) line)
29
name some other solutes that have transport maxima
* sugars (fructose, galactose, glucose) * amino acids * metabolic intermediates (lactate) * phosphate ions * vitamins
30
Osmotic diuresis
is increased urination due to the presence of certain substances in the fluid filtered by the kidneys that cause water to come into the urine
31
what effect does excess unreabsorbed solute (e.g. mannitol) have in the proximal tubule
* manitol: non-reabsorbed carbohydrate can be given IV to induce osmotic diuresis * inhibits osmotic water flow from lumen to basolateral spaces * causes Na+ back diffusion into lumen of tubule with increased Na+ and water loss in urine * **osmotic diuresis**
32
osmotic diuresis results in a rapid loss of what two substances
* sodium and water -\> polyuria
33
name another commonly known disease that causes osmotic diuresis
diabetes: when glucose load exceeds TM , there is excess glucose in filtrate
34
tubular secretion occurs via what two routes
* paracellular * transcellular
35
the two main transport mechanisms present in tubular secretion seperate what compounds
* one is for **organic cations** * one is for **organic anions** * \*\*very non-specific
36
compounds to be secreted by the kidney are tagged for secretion in the liver via what
* glucuronic acid or sulfate
37
organic anions are secreted in the nephron via what type of transport
tertiary active transport
38
how is PAH, an organic anion, secreted across kidney cell
1. PAH is taken up into the cell in exchange for **alpha-KG** 2. PAH leaves the cell on the apical side via a PAH-anion antiporter
39
why does elevated plasma levels on one anion inhibit secretion of others?
all organic anions compete for the same transporter * ex: infusion of PAH inhibits the secretion of Penicillin, extending its life
40
Why does the inulin concetration increases (Tubular fluid/plasma concentration) in the proximal tubule
inulin is neither secreted or reabsorbed but water is reabsorbed making the concentration of inulin in the proximal tubule increase
41
Why does the sodium concetration appear not to change (Tubular fluid/plasma concentration) in the proximal tubule even though you know 2/3 is reabsorbed?
equal amount of water are being reabsorbed with it

Hum Physiology II (12 decks)

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