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Physiology 2 > L4: Tubular Transport > Flashcards

L4: Tubular Transport Flashcards

1
Q

What is the equation to find filtered load?

A

FL= (GFR) (Px)

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2
Q

What is the equation to find excretion rate?

A

ER= (Ux)(V)

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3
Q

Define transport rate and what is the equation to find it?

A

The amount of material added to (secreted) or removed (reabsorbed) from glomerular filtrate.

Tx= FL -ER

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4
Q

What does it mean if the transport rate is positive?

A

Some material was removed from the filtrate by reabsorption

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5
Q

What does it mean if the transport rate is negative?

A

Some material was added to the filtrate by secretion

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6
Q

What are the two routes of reabsorption?

A

Paracelluar (between cells in leaky epithelium gap junctions, or transcellular (through the cell)

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7
Q

What are the mechanisms that facilitate transcellular transport?

A

Simple diffusion, faciliated diffusion, primary active transport, secondary active transport, and endocytosis

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8
Q

The proximal tubule (reabsorbs/secretes) *** of the water.

A

Reabsorbed 2/3s

***water follows sodium out

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9
Q

Why does the peritubular capillary next to the proximal tubule have high fluid reabsorption?

A

It has high peritubular capillary oncotic pressure (drives fluid in)

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10
Q

How does Na+ enter the peritubular cells?

A

Either by cotransport with organics or by Na+/H+ antiport (NHE)

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11
Q

How does Na+ leaves the peritubular cells?

A

Na+/K+ ATPase or cotransport with bicarbonate

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12
Q

How does angiotensin affect proximal tubule reabsorption?

A

It stimulates Na+/H+ exchange across apical membrane (NHE transporters) therefore increasing Na+ reabsorption and H+ secretion

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13
Q

How does the sympathetic nervous system affect Na+ reabsorption in the proximal tubule?

A

SNS activity stimulates Na+ reabsorption

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14
Q

How does the parathyroid hormone affect Na+ reabsorption in the proximal tubule?

A

PTH is released with low serum calcium and inhibits Na+/phosphate cotransport. This increases urinary excretion of phosphate

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15
Q

What does it mean if the TF/Px ratio is 1?

A

Reabsorption of the solute has been exactly proportional to the reabsorption of water

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16
Q

What does it mean if the TF/Px ratio is <1?

A

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

17
Q

What does it mean if the TF/Px ratio is >1?

A

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

18
Q

What is the tubular maximum?

A

The maximal rate at which the renal transport system can transport a particular solute

19
Q

What do the portions above and below Tm mean?

A

Below Tm: all the filtered load is reabsorbed

Above Tm: excreted

20
Q

What is the threshold for reabsorption?

A

The point where glucose first appears in the urine

21
Q

Does decreases GFR increase or decrease the threshold?

A

Increase

22
Q

What is osmotic diuresis and what does it do?

A

Excess unreabsorbed solute inhibits osmotic water flow from lumen to basolateral spaces. This causes Na+ back diffusion into the tubular lumen with increased Na+ and water loss

23
Q

What is mannitol?

A

An osmotic diuretic that increases loss of water and electrolytes
-nonreabsorbed carb

24
Q

What are the two things that osmotic diuresis can accompany?

A
  • high filtered load of urea because urea can act as an osmotic diuretic
  • when glucose exceeds Tm in diabetic patients
25
Q

What are the two main transport mechanisms for tubular secretion?

A

Organic cations and organic anions

-very nonspecific

26
Q

Organic anions are secreted via ***.

A

Tertiary active transport

27
Q

PAH is taken into the cell from the blood in exchange for ***.

A

Alpha ketoglutarate

28
Q

What is the transporter for PAH and alpha ketoglutarate?

A

OAT- organic acid transporter

*most organic anion secretion involved OAT-1 and OAT 3 transporters in the basolateral membranes of proximal tubule cells

29
Q

Organic cation transport is handled by several ** transporters, also in the **.

A

OCT

Proximal tubule

30
Q

How is Na+ transported across the basolateral membrane in the proximal tubule?

A

Na/K ATPase or with HCO3

31
Q

What part of the nephron are NHE transporters located in?

A

Proximal tubule on the apical side

32
Q

What part of the nephron does mannitol exert it effects?

A

The proximal tubule

33
Q

Most organic ion secretion involves ** transporters on the basolateral side of the ** cells.

A

OAT 1 and OAT 2

Proximal tubule

34
Q

Other than mannitol, what else can act as an osmotic diuretic in the proximal tubule?

A

Excess glucose, filtered load must exceed tubular maximum

Physiology 2 (13 decks)

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