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Urinary > Lecture 7 - Control of plasma volume > Flashcards

Lecture 7 - Control of plasma volume Flashcards

1
Q

Major osmotically effective solute in ECF

A

Na+

Water in ECF dependent on Na+

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2
Q

Na+

A

Determines:

  • ECF volume
  • Plasma volume
  • Blood pressure
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3
Q

ECF contraction

A

Na+ excretion is more than Na+ ingested

ECF volume decreases as water is excreted decreasing BP

Negative balance

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4
Q

ECF expansion

A

Na+ excretion is less than the Na+ ingested

The extra Na+ is retained in ECF therefore volume increases and water is drawn out of the nephron
Increases BP
Positive balance

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5
Q

ECF volume detectors

A

Low pressure baroreceptors

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6
Q

Transcellular reabsorption

A

From cell to cell

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7
Q

Paracellular reabsorption

A

in between cells

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8
Q

Basolateral membrane

A

Contains the 3Na+/ 2K+ ATPase - driving force for secondary active transport

Na+/HCO3- cotransporter

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9
Q

Apical membrane

A

Lumen to epithelial cell

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10
Q

Proximal convoluted tubule transporters

A 
Na+ / H+ antiporter (exchanger)
Na+ / glucose symporter
Na+ / AA co transporter 
Na/ Pi
Aquaporins
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11
Q

Loop of Henle transporters

A

NaKCC2 symporter

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12
Q

Eary distal convoluted tubule transporters

A

Na+/ Cl- symporter

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13
Q

Late DCT and collecting duct transporters

A

ENaC - epithelial Na Channels

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14
Q

Reabsorption

A

Movement of water and solutes from the nephron tubule into the circulation

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15
Q

Secretion

A

Movement of water and solutes from the circulation into the nephron tubule

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16
Q

PCT

A 
Reabsorption of: 
Na+
Cl- - paracellular 
K+
Ca2+
Urea
Glucose 
Amino acids
HCO3-  ( via carbonic anhydrase)
H2O

Secretion of:
Creatinine
Drugs
H+

17
Q

Descending limb

A

Water reabsorption

lots of aquaporin channels and gap junctions

18
Q

Ascending limb

A

NO water absorption as no aquaporins

Na+ , Cl- and K+ reabsorption takes place - NKCC2

19
Q

DCT

A 
Reabsorption of:
Na+ 
Cl- 
Mg+ and Ca2+ - paracellular inbetween tight junctions
HCO3-

Secretion of:
H+
K+
Contains Na+/K+ transporter - (aldosterone)

20
Q

Collecting duct

A 
Reabsorption of:
Na+ 
Cl- 
Urea 
H2O - aquaporins
21
Q

Aldosterone

A

Produced and secreted by the adrenal cortex
In response to low BP
More Na+ reabsorbed thus more water
More K+ secreted - hypokalaemia

22
Q

ADH

A

Increase expression of aquaporins in collecting duct

Increase H2O reabsorption

23
Q

Amiloride

A

Diuretic
Inhibits NHE in PCT
Inhibits ENaC in DCT
Less Na+ reabsorbed so less water reabsorbed

24
Q

Loop diuretics - Furosemide

A

Furosemide - Inhibits NKCC2 in thick ascending limb

Less Na + reabsorption therefore less water reabsorption

Can cause hypokaleamia

Less vasoconstriction in afferent arteriole due to macula densa NKCC2 inhibition

25
Q

K+ sparing diuretic

A

Spironolactone - Inhibits ROMK

Less K+ excreted so the concentration gradient inside the epithelium decreases.

NKCC2 works less efficiently due to diminished gradient

26
Q

Thiazides

A

Inhibits Na+/Cl- (NCCT)

27
Q

Cell type of loop of Henle

A

squamous epithelium

few mitochondria

28
Q

Passive Na+ reuptake in thin ascending limb

A

water reabsorption in the descending limb creates a gradient for passive Na + reabsorption paracellularly

29
Q

Intercalated cell type A

A

Secrete H+

30
Q

Intercalated cell type B

A

Secrete HCO3-

31
Q

Ca2+ reabsorption

A
  1. Apical channels in the DCT transport Ca2+ into the epithelium
  2. It immediately binds to calbindin which shuttles it across to the basolateral membrane
  3. Ca2+ is transported to the capillary via NCX
  4. Tightly regulated by calcitriol and PTH
32
Q

Principal cells

A

Contains ROMK and ENaC on their apical surface

33
Q

Glucosuria

A

When the glucose transport maximum is reached, it exceeds the transporter capacity and therefore is excreted into the urine.

34
Q

How is HCO3- reabsorbed in the PCT?

A
  1. The PCT contains NHE on its apical surface which secretes H+ ions into the lumen
  2. HCO3- in the lumen reacts with H+ to produce H2CO3 (carbonic acid)
  3. Carbonic acid is converted to CO2 and H2O by carbonic anhydrase.
  4. CO2 is transferred into the tubular cells via transcellular transport.
  5. Via carbonic anhydrase CO2 reacts with water to form HCO3- and H+
  6. The HCO3- is reabsorbed into the capillary via Cl- / HCO3- (anion exchanger) - non-sodium dependent

Urinary (23 decks)

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