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GU1 - Nephrology > Phys 3 > Flashcards

Phys 3 Flashcards

1
Q

Reabsorption in PCT

A
  • location of most active reabsorption
  • all glucose and aa
  • 60-80% of Na+
  • 75-85% of water
  • K+
  • Urea
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2
Q

PCT

  • overall change to filtrate
  • secretion
A
  • filtrate volume reduced by 80%

- secretion of nitrogenous wastes

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3
Q

Descending loop of Henle

  • permeability
  • filtrate changes
A
  • freely permeable to water
  • not permeable to NaCl
  • filtrate is concentrated by water resorption
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4
Q

why does water exit descending loop of Henle?

A

exits based on osmotic gradient of cortical and medullary interstitial fluid

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5
Q

Ascending loop of Henle

  • permeability
  • filtrate changes
A
  • freely permeable to NaCl
  • not permeable to water
  • dilute filtrate formed
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6
Q

Why does Na+ leave the Ascending loop of Henle, what does it contribute to

A

actively transported out

- contributes to high osmolarity of the medullary ECF

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7
Q

DCT

  • absorption
  • secretion
A 
selective absorption and secretion
Absorption
- HCO3-
- Na+ (under Aldosterone control)
- Water (ADH control)

secretion:
- NH4 and H+

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8
Q

What happens to filtrate as it moves through DCT

A

becomes more concentrated as water is absorbed

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9
Q

CD reabsorption & secretion

A
  • urine is concentrated along medulla
  • reabsorption/secretion to maintain blood pH (K+, H+, HCO3-, Cl-)
  • urea diffuses via transporters to medulla, helps contribute to high osmolarity
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10
Q

Tubular secretion

- functions

A
  • dispose of unwanted substances not in filtrate such as drugs
  • eliminate unwanted substances that have been reabsorbed by passive processes
  • K+ elimination (via aldosterone)
  • Control of blood pH
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11
Q

How does tubular secretion change as blood becomes acidic

A
  • actively secrete H+ into filtrate (acidify urine)

- reabsorb HCO3- and K+

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12
Q

How does tubular secretion change as blood becomes alkaline

A
  • HCO3- is secreted
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13
Q

How is the flow of blood related to the flow through the nephron?

A

countercurrent

  • creates opportunities for osmotic movement with help from highly osmotic gradient of medullary interstitium
  • as blood flows past ascending limb absorbs ions, becomes hypertonic
  • then when passes descending limb water easily moves into blood dt osmotic pressure of ions
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14
Q

Vasa recta

- function

A
  • maintain osmotic gradient
  • deliver nutrient supply
  • sluggish blood flow
  • freely permeable to water and salt (vs. loop of Henle which is differentially permeable)
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15
Q

Volume of water in

  • the body
  • ICF
  • ECF
A

Total: 40 L
ICF: 25 L
ECF: 15 L (interstitial fluid and plasma)

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16
Q

Composition of body fluids

  • what maintains
  • ICF ion
  • ECF ion
A
  • Na/K pump
  • ICF: K+
  • ECF: Na+

*bc osmolality is equal between ECF and ICF, the NET change between the two is zero even though lots of ion, etc. flow between

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17
Q

Tonicity

definition

A

ability of a solution to change the tone of cells

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18
Q

Isotonic

- example

A

Physiological saline soln (PSS)

- 0.9% sodium w/v, 308 mOsmol

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19
Q

what happens to cells in solutions that are:
Hypotonic
Hypertonic

A

hypo: swell, lysis
hyper: shrivel, crenation

20
Q

What happens when there is a mismatch in osmolality of body fluids between electrolyte intake and loss

A

change in osmolality of body fluids - physiologic issues that must be fixed

21
Q

What two things happen when there is an increase osmolality of ECF?

A
  • thirst: drink more water, dilute ECF

- ADH secretion: water retention, dilute ECF

22
Q

Thirst drive for water balance

- two stimuli

A
  • decreased volume of ECF

- increased osmolality of ECF

23
Q

What happens when increased osmolality of ECF occurs?

A
  • decreased saliva secretion
  • dry mouth
  • drink
  • increased water = decreased osmolality
24
Q

what happens when decreased volume of ECF occurs

A
  • stim osmorelceptors in hypothalamic thirst center
  • sensation of thirst,
  • drink
  • increased water = increased volume
25
Q

ADH

  • released from what
  • why released?
A
  • released from posterior pituitary

- in response to hypothalamic stimulus

26
Q

ADH

- 2 receptor types

A

Osmoreceptors

  • in hypothalamus
  • depolarize when >285 mOsm/kg

Baroreceptors

  • great veins, L/R atria, PV
  • respond to low volume
27
Q

ADH

- what other stimuli cause release

A
  • pain
  • nausea
  • surgical stress
  • Ang II in response to hypovolemia
28
Q

ADH

- principle effect

A
  • water retention by kidney

- causes filtrate to become concentrated

29
Q

ADH

- receptor

A
  • V2 receptor
  • on CD cells
  • stimulates insertion of aquaporin 2 into the apical membranes
30
Q

where are aquaporins stored

A

endosomes

- ADH causes rapid translocation to cell membrane

31
Q

ADH

- effects

A
  • water enters hypertonic interstitum of renal pyramids, is reabsorbed
  • osmotic pressure of body fluids decreases
  • urine concentrates, volume decreases
32
Q

In conditions of good hydration and no ADH describe the

  • urine
  • water loss/gain
A
  • urine is hypotonic to plasma
  • urine volume is increased
  • net water loss
33
Q

what is the most important determinant of ECF volume

A

Na+

34
Q

Sodium

  • regulation linked to what
  • regulated by what 3
A
  • regulation linked to blood pressure and blood volume

- regulated by aldosterone, renin, natriuretic peptides (ANP, BNP)

35
Q

what regulatory molecule has the most influence over sodium in the ECF?

A

Aldosterone

36
Q

Aldosterone

A
  • steroid hormone

- produced and released by adrenal cortex

37
Q

Aldosterone is released in response to (2)

A
  1. renin from kidney (via angiotensin II)

2. High serum K+

38
Q

Function of aldosterone

A
  1. increase renal Na+ reabsorption and K+ secretion (water follows Na+)
  2. receptors on DCT and CT
39
Q

Renin

  • released from what
  • in response to what
A 
- released from juxtaglomerular cells
in response to:
1. decreased stretch due to low volume/bp
2. decreased filtrate osmolarity
3. direct SNS stimulation
40
Q

What is the function of Renin/angiotensin system

A
  • cleave angiotensinogen to release angiotensin I

- ACE action produces angiotensin II

41
Q

Functions (3) of Angiotensin II

A
  1. vasoconstriction
    - increases peripheral vascular resistance (after load)
    - increases bp
  2. aldosterone secretion from renal cortex
    - reabsorb Na+, increase blood volume and bp
    - secretion of K+
  3. feedback inhibition of renin
42
Q

Natriuretic peptides

- two types

A
  1. ANP: atrial natriuretic peptide (atrial myocytes)

2. BNP: B-type natriuretic peptide (ventricle)

43
Q

Natriuretic peptides

- released in response to what

A

stretch - increased blood volume/bp

44
Q

Natriuretic peptides

- action

A
  • decrease blood volume/bp
  • kidney:
  • increase GFR dt vasodilation
  • inhibit Na+ reabsorption by tubules
  • decrease renin - inhibit aldosterone
  • vascular smooth muscle relaxation (vasodilation)
45
Q

Potassium

  • essential for what
  • other very important function
A
  • essential for membrane potential, esp in heart

- important in pH buffering systems (H+ movement is balanced by K+ countermovement)

46
Q

What controls K+ balance

A

renal mechanisms under influence of aldosterone (directly sensitive to increased K+)

47
Q

How does body remove excess K+?

A

Aldosterone causes increased Na+ reabsorption by tubules

- concomitant secretion of K+ due to Na/K pump

GU1 - Nephrology (16 decks)

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