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BIOE340 > filtration, reabsorption, and secretion (midterm 3) > Flashcards

filtration, reabsorption, and secretion (midterm 3) Flashcards

1
Q

what is GFR

A

glomerular filtration rate, the rate of fluid extraction from the glomerular capillaries into Bowman’ capsule (~180 L/day - ~ 2 mL/min into Bowman’s)

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2
Q

what are the 3 major layers of the glomerular capillary membranes (most cap membranes only have 2!)

A
  • the endothelium of the capillary
  • a basement membrane
  • a layer of epithelial cells (podocytes) surrounding the outer surface of the capillary basement membrane
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3
Q

what is filtered in glomerular filtration and at what rate compared to water

A
  • Sodium, glucose, and inulin are filtered as freely as water
  • Myoglobin is filtered 75% as rapidly as water; albumin 0.5% as water
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4
Q

what is the equation for GFR

A

Kf (filtration coefficient) x (PG - PB - πG + πB)
PG = glomerular hydrostatic pressure
PB = Bowman’s capsule hydrostatic pressure
πG = glomerular capillary colloid osmotic pressure
πB = Bowman’s capsule colloid osmotic pressure

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5
Q

what is net filtration favored by

A

glomerular hydrostatic pressure (PG) and Bowman’s capsule colloid osmotic pressure ( πB)
- typically, πB ~ 0 because there is no protein transport into Bowman’s capsule

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6
Q

what is the major determinant of GFR

A

PG - increased PG = increased GFR

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7
Q

what is PB usually and what does it do to GFR

A

18 mmHg - reduces GFR

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8
Q

what happens to GFR with πG

A

increased πG = decreased GFR

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9
Q

what are the three things glomerular hydrostatic pressure is determined by

A
  • Arterial pressure (increased arterial pressure increases glomerular hydrostatic pressure and GFR)
  • Afferent arteriolar resistance (increased resistance reduces glomerular hydrostatic pressure and decreases GFR)
  • Efferent arteriolar resistance (increased resistance (up to a point!) reduces glomerular capillary outflow, increases glomerular hydrostatic pressure and increases GFR)
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10
Q

what is the total renal blood flow of a 70 kg person

A

1200 mL/min (21% of cardiac output)

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11
Q

in normal vs renal tissue, what is the correlation between BF and metabolic demand

A

normal: BF = metabolic demand
renal: BF > renal metabolic demand

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12
Q

what do vasoconstrictors do to GFR

A

they decrease blood flow and therefore decrease GFR

norepinephrine, epinephrine

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13
Q

what do vasodilators do to GFR

A

they decrease renal vasculature resistance, increase BF, and increase GFR

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14
Q

what does increased sympathetic stimulation do to GFR

A

decreases renal arterial diameter, decreases BF, decreases GFR

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15
Q

what is tubuloglomerular feedback

A

changes in sodium chloride concentration causes changes in the macula densa, that then control renal arteriolar resistance (graph on pg 13 of notes/ desktop)

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16
Q

what is urinary excretion rate equal to

A

filtration rate minus reabsorption rate plus secretion rate

17
Q

how do glomerular filtration and tubular reabsorption compare to urinary excretion

A

they are very large relative to it

18
Q

are glomerular filtration and tubular reabsorption selective

A

glomerular filtration is non-selective

tubular reabsorption and secretion is highly selective

19
Q

what does filtration lead to

A

reabsorption

20
Q

what are the transport mechanisms during reabsorption

A

tubular epithelium -> interstitial space -> peritubular capillary endothelium

21
Q

what is primary active transport through the tubular membrane linked to

A

the hydrolysis of ATP via
- Sodium-potassium ATPase
- Hydrogen ATPase
- Hydrogen-potassium ATPase
- Calcium ATPase

22
Q

what does secondary active transport through the tubular membrane involve

A

Na+/glucose co-transport
Na+/amino acid co-transport
Na+/H+ counter-transport

23
Q

do active transport and passive transport have limits

A

active transport has a maximum limit
passive transport has no limit

24
Q

what is passive transport determined by

A

electrochemical gradient
membrane permeability
fluid retention time within the tubule

25
Q

what does sodium transport do

A

drives water reabsorption by osmosis

26
Q

what is the concentration of molecules along the nephron a result of

A

the individual molecules’ transport and the transport of water

27
Q

what is the concentration of sodium, glucose, and creatine/urea along the nephron + how they are transported

A
  • Sodium is highly transported, but its concentration does not change as water is also highly removed
  • Glucose concentration falls dramatically, as it is transported much more quickly than water
  • Creatinine and urea increase in
    concentration and urea is not reabsorbed
28
Q

what are the three segments of the loop of Henle

A
  • descending thin segment (highly permeable to water)
  • ascending thin segment
  • thick ascending segment (thick epithelial cells capable of active reabsorption of sodium, chloride, and potassium - ~ 25% of these filtered molecules are reabsorbed here)
29
Q

how is the distal tubule of a nephron similar to the loop of Henle

A

they both reabsorb most ions including sodium, potassium and chloride, but are impermeable to water and urea

30
Q

what two cell types do the late distal tubule and cortical collecting tubule contain

A
  • principal cells, which reabsorb sodium and water and as secrete potassium
  • intercalated cells, which reabsorb potassium and secrete hydrogen
31
Q

what is glomerulotubular balance

A

increased GFR => increased tubular resistance (proximal tubular reabsorption is 65% of GFR)

32
Q

what is the equation for tubular reabsorption and what does everything stand for

A

Kf x (-Pc + Pif + πc - πif)
- Peritubular hydrostatic pressure (Pc)
- Renal interstitium hydrostatic pressure (Pif)
- Peritubular colloid osmotic pressure (πc)
- Renal interstitium colloid osmotic pressure (πif)

33
Q

what are Pc and πc functions of and what do they do to absorption

A

Pc = f(Pa) (increased Pa, increased Pc => decreased reabsorption
and Pc = f(Ra, E) (decreased Ra, E (resistance of afferent and efferent arterioles), increased Pc => decreased reabsorption)
πc = f(πA) (increased πA, increased πc => increased reabsorption)
and πc = f(FF) (increased filtration fraction, increased plasma F, increased plasma (protein), increased πc => increased reabsorption

34
Q

what is the effect of arterial pressure regulation between 75 and 160 mmHg

A

only a slight effect on renal BF and GFR

35
Q

what happens when GFR auto regulation is impaired

A

arterial pressure can cause large increases in GFR and a greater effect on sodium and water excretion

BIOE340 (18 decks)

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