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MSAP Review > Renal Physiology > Flashcards

Renal Physiology Flashcards

1
Q

Basic Function of the Kidney

A

1) Urine Production Via Filtration and Reabsorption 2) Regulation of blood and cleaning/filtering 3) Secretion of hormones in response to blood. Ex) Renin, Erythropoietin, VitD 99% of filtration gets reabsorbed by body

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2
Q

List and identify structure of nephron

A
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3
Q

List the vasculature associated with the nephron

A

1) Afferent arteriole => brings blood into the glomerulus for filtration.
2) Efferent arteriole => bring blood out that has reabsobed substances from nephron.
3) Peritubular capillaries => Tiny blood vessels of the efferent arterioles that surround the PCT and DCT and are crucial in reabsorption.
4) Vasa Recta => Extension of the peritubular capillaries that surround the loop of henle.

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4
Q

What are the two types of nephrons found in the kidney

A

1) Cortical
2) Juxtaglomerular

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5
Q

Function of juxtamedullary vs cortical nephron

A

Juxtamedullary => more responsible for the concentration of urine (minority of nephrons in kidney)

Cortial => Excretion of waste (Majority of nephrons in kidney)

Big take away from lecture was Juxtamedullary is the nephron that is mainly involved in urine production.

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6
Q

Structural differences between the cortial and juxtamedullary nephron

A

Cortical:

  • Glomerulus in upper region of cortex
  • Only a small part of the loop of Henle is in medullary
  • Does NOT have a thin ascending tubule

Juxtaglomerular:

  • Glomerulus is near the border of cortex and medulla
  • Loop of Henle runs deep in medulla
  • Contains both a thin and thick acending limb
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7
Q

Basement membrane of glomerulus

A

Bowman’s capsule

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8
Q

What are podocytes

A

Specialized cells of the glomerulus that wrap around capillaries and that neighbor cells of the Bowman’s capsule

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9
Q

An extension of the podocytes

A

Pedicels

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10
Q

What do pedicels form

A

Form filtration slits

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11
Q

Permeability of filtrate through the glomerulus is dependent upon

A

Size and charge

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12
Q

Filtrate that is less that 15 Angstroms are _____ where are substrate greater than 35 Angstroms are _____.

A

Freely filtered

Not filtered

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13
Q

At what range of size is filtration possible but limited

A

Between 15A - 35A

Closer to 15A => easier the filtering

Closer to 35A => harder the filtering

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14
Q

Explain how charge can play a role in filtration.

A

Pedicels (filtration slits) have a highly negative charge. Therefore, there is an electrostatic attraction between filtrate with a charged cation.

Charge has a larger affect on filtration rate than size.

Example) A 15A negatively charged particle will have a slower filtration rate than a 20A postiviely charged particle.

Although the 20A is bigger, b/c its relatively close to 15A and is positively charged makes it faster.

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15
Q

What is the the concentration of free filtered molecules relative to plasma and Bowman’s Space

A

Concentration of filtrate in PLASMA = Concentration of filtrate in Bowman’s Space

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16
Q

What is the the concentration of non-freely filtered molecules relative to plasma and Bowman’s Space.

A

Concentration of filtrate in PLASMA > Concentration of filtrate in Bowman’s Space

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17
Q

What are the 4 types of Starling forces

A

PGC => Hydrostatic Glomerular Capsule Pressure

πBS => Oncotic Bowman’s Space Pressure

PBS => Hydrostatic Bowman’s Space Pressure

πGC => Oncotic Glomerular Capsule Pressure

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18
Q

Hydrostatic Pressure can be described as

A

Pushing force

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19
Q

Oncotic Presssure can be described as

A

Sucking force

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20
Q

Express the starling forces and how they affect filtration/reabsorption

A
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21
Q

Filtrate goes from glomerulus into _____ and then into ____.

A

Bowman’s Space and Proximal Tubule

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22
Q

Net movements of filtrate can be expressed by what equation and define that equation:

A

Starling Equation:

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23
Q

What do we assume of the oncotic pressure in the Bowman’s Space (πBS)

A

πBS​ = 0 mmHg,

Because proteins are NOT filtered from the Glomerular Capsule into the Bowman’s Space.

If proteins end up being filtered, this is indicative of a physiological disorder.

Diseases/disorders that can cause protein in urine (proteinuria):

Ex) Nephrotic syndrome, Lupus, Goodpasture’s syndrome and Glomerulonephritis

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24
Q

Give an example of something that gives urinary tract obstruction

A

Kidney stone

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25
Q

What part of the kidney can be obstructed by a kidney stone and what net effect does this cause

A

Kidney stone => blockage of renal calyx

Blockage of renal calyx => filtrate cannot leave kidney into ureter

Backing up of filtrate in Bowman’s Space can occur => lead to forced reabsorption rather than filtration.

26
Q

Explain Nephrotic Syndrome

A

Renal Disease in which the Glomerular capillaries are damaged. Damage causes proteins to enter into filtrate.

Why is proteinuria bad. We want proteins to be circulating in our bloodstream. By excreting proteins out of our body, our blood circulating CANNOT be sucking water out of intersitial spaces (onoctic pressure is eliminated).

People with Nephrotic Syndrome have a pooling of H20 in their interstitial spaces.

27
Q

What is edema

A

Swelling caused by excess fluid trapped in your body’s tissues.

28
Q

Rate at which the ultrafiltrate forms in Bowman’s space

A

Glomerular Filtration Rate (GFR)

29
Q

Why is GFR so important

A

Indicative of patient health

30
Q

Equation for GFR

A

Delta P => Derived from Starling equation

Kf => Filtration Coefficient and is invariant (typically from 10-15)

31
Q

Explain how changes in plasma flow affect filtration rate:

A
32
Q

Movement of solutes from glomerular capillaries to Bowman’s space

A

Filtration

33
Q

Return most filtered solutes to circulation

A

Reabsorption

34
Q

Transport of solutes from the peritubular capillaries and Vasa Recta into the tubular lumen.

A

Secretion

35
Q

Solute in urine due to filtration, secretion, and reabsorption

A

Excretion

36
Q

67% of reabsorption into the peritubular capillaries

A

At PCT (proximal convoluted tubules)

**REMEMBER: Peritubular capillaries are an extension of efferent arterioles.

37
Q

Define Autoregulation

A

Maintain balanced GFR flow to mediate reabsorption

38
Q

What happens if blood pressure falls below a normal range

A

Low blood pressure => low renal plasma blood flow => low GFR => hemorrhage/heart failure

*hemorrhage => ruptured blood vessel

39
Q

What happens if blood pressure falls above a normal range

A

High blood pressure (hypertension) => High renal plasma blood flow => High GFR => tachycardia

40
Q

Name the two ways in which autoregulation occurs:

A

1) Myogenic Response
2) Tubular Glomerular Feedback

41
Q

Explain where filtration, reabsoprtion, secretion and excretion are occuring in the nephron

A
42
Q

Why is it bad if GFR is too high

A

Filtration is too much and not enough reabsorption is occuring in the body. Patient is peeing out alot of necessary substances.

43
Q

Why is it bad if GFR is way too low

A

Reabsorption is too much and not enough filtration is occuring in the body. Waste especially is reabsorbed.

44
Q

Explain the kidney’s myogenic response to maintain homeostatic GFR

A

If there is high GFR in the afferent arteriole => stretch occurs.

Stretch receptors are activated and opening of Ca2+ channels occur. Ca2+ channels constrict the afferent arteriole to lower GFR

45
Q

Explain the kidney’s Tubuloglomerular response to maintain homeostatic GFR

A

Involves Macula Densa Cells.

These cells sense GFR flow via NaCl content.

If there is severe change in GFR, Juxtaglomerular cells are signal a vasoactive response.

1) High GFR => High Filtration.

Kidney releases Adenosine. Adenosine => Constricts afferent arteriole => lowers GFR to normal

2) Low GFR = > Low Filtration

Kidney releases Renin. Renin catalyzes Angiotensinogen to Angiotensin-I. Then Angiotensin-1 is converted to Angiotensin-II by ACE.

Angiotensin-ll => Constrict efferent arteriole to elevate GFR back to normal.

46
Q

In a health person, what is the relationship between Na+ intake and Na+ excretion

A

Na+ intake = Na+ excretion

47
Q

A person who has more Na+ intake> Na+ excretion is said to have

A

High blood pressure and blood volume

48
Q

A person who has more Na+ intake< Na+ excretion is said to have

A

low blood pressure and blood volume

49
Q

What occurs at the early proximal convoluted tubule

A

30-35% Na+ reabsorption

Na+ draws H20 reabsorption

50
Q

What occurs at the late proximal convoluted tubule

A

~35% Na+ reabsorption

Na+ draws H20 reabsorption

51
Q

What occurs at the thick ascending limb

A

25% Na+ reabsorption

(No H2O)

52
Q

What occurs at early distal tubule

A

5% Na+ reabsorption

53
Q

Late Distal Tubule and Collecting Duct

A

3% Na+ Reabsorption

54
Q

Explain how the RAAS system work and when it is activated

A

When there is LOW Na+ intake (and HIGH Na+ excretion) => LOW BLOOD PRESSURE

Sympathetic Response => RAAS:

Angiotensinogen => Angiotensin-I => Angiotensin-ll => Aldosterone

Aldosterone => increases Na+ and water reabsorption (acts on principal cells)

RAAS => raised blood pressure

55
Q

Describe some of the actions of Angiotensin-ll

A

=> Stimulates aldosterone secretion

=> Constricts efferent arteriole

=> Stimulates thirst

=>Stimulates Na+ reabsorption at PCT

56
Q

What is Atrial Natriuretic Peptide (ANP) and when is it released.

A

ANP is a hormone secreated by atria when there is a heavy intake of Na+ (increase in ECF volume and blood pressure).

ANP is secreted out from the heart in response to stretch and increases GFR. This encourages filtration and inhibits reabsorption of Na+.

It also inhibits aldosterone.

ANP => REDUCES B/P

57
Q

What function do anti-diuretics serve

A

=> Urinary Retention

58
Q

What is ADH

A

Anti-diuretic hormone (vasopressin). Its a hormone that works on Distal and Collecting duct to reabsorb water.

ADH binds to a G-Protein receptor and causes a release of cAMP in principal cells. => Aquaporin H20 channels are activated in the principal cells to stimulate water reabsorption.

59
Q

How is ADH activated

A

1) By a 1 mOSm/L rise in plasma (more solutes and less water)
2) Hypovolemia => loss of blood volume

60
Q

What actions does angiotensin II have that are not related to its ability to vasoconstrict? Angiotensin II:

A

Increases Na+ reabsorption by proximal tubule

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