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Physiology > 4 Tubular Transport > Flashcards

4 Tubular Transport Flashcards

1
Q

Review: what are the components of rena function?

A
  1. Glomerular filtration (filtering the plasma of proteins)
  2. Tubular reabsorption (from tubular lumen to PTC)
  3. Tubular secretion (from PTC to tubular lumen)
  4. Excretion (not secretion….loss from body in the urine)
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2
Q

Filtered load is the amount of material in _____________: FL = ? (formula)

A

glomerular filtrate;

FL = (GFR)(Px)

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3
Q

Excretion rate is the amount of material ___________.

ER = (formula) ?

A

lost in urine;

ER = (Ux)(V)

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4
Q

Secretion vs. Reabsorption: Transport rates (Tx) are amount of material added to (secreted) or removed (reabsorbed) from glomerular filtrate

Tx = ? (formula)

A

Tx = FL - ER

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5
Q

Secretion vs. Reabsorption:

If the transport rate (Tx) is positive, then some material was ___________.

A

Reabsorbed (removed from the filtrate)

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6
Q

Secretion vs. Reabsorption:

If the transport rate (Tx) is negative, then some material was ___________.

A

secreted (added to thhe filtrate)

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7
Q

Fractional Excretion is the ratio of excretion rate over _________.

A

filtered load

FE = ER / FL

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8
Q

Fractional excretion:

If FE < 1, then some material was __________.

A

Reabsorbed (opposite of transport rate: negative –> secretion)

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9
Q

Fractional excretion:

If FE > 1, then some material was __________.

A

secreted (added to the filtrate) (opposite of transport rate which if positive –> reabsorption)

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10
Q

Tubular reabsorption:

Name 2 routes of reabsorption though the tubular epithelial cells

A

Paracellular (between cells) - “leaky” epithelium

Transcellular (through cells) - crosses 2 barriers –> luminal __membrane (apical) and basolateral membrane

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11
Q

About ____% of Na+ (active) and water (passive;solute-linked) are absorbed in the proximal tubule.

Loop of henle has ____% (Na+) and ___% (water) absorption

The distal and collecting tubes have ____% Na+ and ___% water reabsorption

A

Proximal tube: Na+: 67% (active) Water: 65% (passive; solute-linked)

Loop of henle: Na+: 25% (active) Water: 15% (passive; solute-linked)

Distal and Collecting Tube: Na+: 8% (active; aldosterone) Water: 20% (passive; NOT soulte-linked; regulated by ADH)

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12
Q

In the proximal tubule, LOH, and the distal and collecting tubules, Na+ reabsorption is _________. (active/passive?)

A

Active

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13
Q

Water reabsorption in the proximall, LOH, and distal and collecting tubules is _________. (passive/active?)

A

passive

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14
Q

By what mechanisms does Na+ enter the proximal tubule fromt the PTC? How does it leave the cell?

A

Cotransport with organics and a **Na+/H+ ion exchanger (NHE) **(Na+ reabsorption and H+ secretion)

Na+/K+ ATPase and through cotransport with HCO3-

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15
Q

How does Cl- enter the PTC?

A

It travels through paracellular routes (inbeetween cells)

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16
Q

What 3 hormonal and neural influences affect Na+ reabsorption by the PT? What are the effects?

A

Angiotensin II - stimulates Na+/H+ exchange across apicl membrane –> stimulates Na+ reabsorption and H+ secretion

Sympathetic nerve activity - stimulates Na+ reasorption

Parathyroid hormone - inhibits Na+-phosphate cotransport –> increases urinary escretion of phosphate

17
Q

TF/P ratios for freely filtered solutes are ___ in Bowman’s space (proximal tubule).

Water and solute are ________ along length of PT.

Inulin ratio (not secreted or reabsorbed) shows that the volume of tubule fluid is ___________.

Reabsorption can produce very _____ TF/P ratios.

Note that the osmolarity _________.

A

1

reabsorbed

decreasing

small

doesn’t change

18
Q

TF/Px Ratio

If TF/Px = 1.0, then reabsorption has been ______________ to the reabsorption of water.

If TF/Px < 1.0, then reabsorption of the substance has been ______ than water.

If TF/Px > 1.0, then reabsorption of the substance has been ______ than water OR there has been net ________ of the substance.

TF/P(inulin) is used as a marker. Since it is only filtered, it’s concentration in the tube is solely detemined by the movement of ________.

A

exactly proportional

greater

less; secretion

water

19
Q

Tubular Maxima

Tubular maximum (Tm) - maximal rate at which a renal transport system can _________ a __________.

The rate is limited due to saturation of ________ ________ ________.

Below Tm, all of the filtered load is ___________.

The portion of the load above Tm is __________.

Tm’s are foudn primarily in the _________ ________.

A

transport; solute

membrane transport proteins

reabsorbed

excreted

proximal tubule

20
Q

The threshold for the glucose tubular maximum is the plasma concentration where glucose first ________________. Depends on ______.

“Splay” - due to _______ of nephrons. Not all nephrons have the same Tm.

A

appears in urine

GFR

heterogeneity

21
Q

The Effect of Changing GFR on Threshold

Decreasing the GFR _________ (increases/decreases) the threshold.

A

decreases

22
Q

Other Solutes with Tm’s

  • Sugars (fructose, galactose)
  • Amino acids
  • Metabolic intermediates
  • Phosphate ions
  • Water-soluble vitamins
  • Proteins peptide
A
23
Q

Osmotic Diuresis - Proximal Tubule

Excess reabsorbed solute (e.g. mannitol) __________ osmotic water flow from lumen to basolateral spaces.

Causes Na+ ________ into lumen of tubule w/ increased Na+ and water loss (diuresis).

Causes _________ loss of water and electrolytes in urine.

A

inhibits

back-diffusion

increased

24
Q

Osmotic Diuresis can result in a rapid loss of _____ and _____.

Can accompany;

  • a high filtered load of _____
  • when glucose load _______ Tm in diabetic patients (excess glucose in filtrate)

________, a non-reabsorbed carbohydrate can be given IV to induce an osmotic diuresis.

A

sodium and water

urea

exceeds

Mannitol

25
Q

Tubular Secretion

Two routes?

Two main transport mechanisms present…**VERY NON-SPECIFIC **

  1. One for organic ______
  2. One for organic ______

Commpounds secreted

  • metabolites
  • waste products
  • foreign chemicals (tagged by liver e.g. with glucuronic acid or sulfate)
A

Paracellular, transcellular

  1. organic cations
  2. organic anions
26
Q

Secretion of Organic Anions - PAH

Draw out the secretion of organic anions - PAH

  • Organic anions are secreted via _______ _______ transport.
  • PAH is taken up into the celll in exchange for _______
  • PAH leaves the cell on the _______ side via a ________.
A

Tertiary active transport

alpha-KG

apical; PAH-anion antiporter

27
Q

Clinical Tidbits - Anion Transport

All organic anions compete for the same _______.

Thus, elevated _______ _______ of one anion will inhibit the secretion of others.

Ex: infusion of PAH inhibits the secretion of PCN, thus _________ PCN’s half-life.

During WWII, when PCN was in short supply, ________ were infused to extend the drug’s therapeutic effect.tranpo

A

transporter

plasma levels

extend

Physiology (5 decks)

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