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2023 Systems Phys > Renal - Intro to Renal Physiology > Flashcards

Renal - Intro to Renal Physiology Flashcards

1
Q

Define

Internal Sea

A

Salty ECF

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2
Q

How is the internal sea of land vertebrates maintained?

A

By controlling the quanity of H2O and Plasma Constituents

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3
Q

Kidney Function

When there is a surplus of H2O or ions in ECF kidneys…

A

Kidneys eliminate in urine

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4
Q

Kidney Function

When there is a deficit of H2O or ions in ECF kidneys…

A

Kidneys limit losses until more is ingested

H2O or ions are stored/held onto until more is ingested (not in urine)

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5
Q

What are the main functions of the kidney?

A

Eliminate waste/toxins (endogenous and exogenous)
Regulation of Water and Electrolyte Balances
Regulation of Erthrocyte Production
Regulation of 1,25-Dihydroxyvitamin D3 (calcitriol) production
Regulation of Acid-Base Balance

A WET BED

Acid-base balance, Water removal, Erthropoiesis, Toxin removal, Blood pressure control, Electrolyte balance, Vitamin D activation

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6
Q

Kidney Function

Electrolyte balance

What does it control and why?

A

Control of ECF osmolarity essential for maintenance of cell volume
Control of ECF volume key to long-term regulation of BP

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7
Q

Kidney Function

Erthropoiesis

A

Kindey secretes erythropoietin which stimulates the production of RBCs in bone marrow

Not enough erythropoietin can cause anemia

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8
Q

Kidney Function

Vitamin D activation

A

Increasing VD in intestines, increases reabsorption of plasma calcium and PO4^3-

1,25-Dihydroxyvitamin D3 (calcitriol)

Calcitrol is the final product of VD -> when not enough calcium is obtained from bones

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9
Q

Kidney Function

Acid-Base Balance

A

Kidney has a pivotal role: distribuances can be completely corrected thru changes in H+ secretion and HCO3- reabsorption and production

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10
Q

Pathway

Urine

A
  1. Kidneys form urine
  2. Ureters carry urine to bladder
  3. bladder stores urine
  4. urine is preiodically emptied through urethra
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11
Q

Define

Nephron

A

Functional unit of kidney
2 components: vascular/tubular

1.2 million nephrons/kidney

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12
Q

Renal Blood Supply

Renal blood flow is _ by humoral factors

A

autoregulated

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13
Q

Pathway

Renal Blood Supply

How does blood flow through the renal system?

A
  1. Afferent Arterioles
  2. Glomerular Capillaries (Glomerulus)
  3. Efferent Arterioles
  4. Peritublar Capillaries
  5. Vase recta (sometimes)
  6. renal vein
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14
Q

Renal Blood Supply

Afferent Arterioles

What do they do/where do they go?

A

Brings blood to the glomerular capillaries
1/kidney

Blood “Arrives”

Major area of blood flow control

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15
Q

Renal Blood Supply

Glomerulus

What are they? What do they do?

Glomerular Capillaries

A

Small tuft of capillaries sandwhiched between two arterioles
Filters blood from Afferent Arterioles and drains remaining to Efferent Arterioles

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16
Q

Renal Blood Supply

Efferent Arertioles

What do they do/where do they go?

A

Drains blood from the glomerular capillaries

blood not filtered by glomerulus “exits” to peritubular capillaries

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17
Q

Renal Blood Supply

Peritubular Capillaries

What are they/where do they go?

A

A second bed of capillaries that lie after the efferent arterioles and surround the cortical regions of the nephron
Returns blood from the efferent arterioles to the renal vein

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18
Q

Renal Blood Supply

Vasa Recta

What do they do/where do they go?

A

Specialized capillaries that dip into the renal medulla and surround the loop of Henle

The help maintain the concentration gradient and return fluid to renal vein

Continuation of the Efferent Arteriole in the medulla

Not every peritubular capillary leads to a vasa recta

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19
Q

General Overview

Vascular Component of Nephron

A

Afferent Arteriole
Glomerulus
Efferent Arteriole
Peritubular Capillaries

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20
Q

General Overview

Tubular Component of Nephron

A

Bowman’s Capsule
Proximal Tubule
Loop of Henle
Distal tubule
Collecting duct

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21
Q

General Overview

Combined Vascular/Tubular component of Nephron

A

Juxtaglomerular Apparatus

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22
Q

General Overview of Nephron Functions

Afferent Arteriole

Generally Define Function

A

Carries blood to the glomerulus

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23
Q

General Overview of Nephron Function

Glomerulus

Generally Define Function

A

A tuft of capillaries that filters a protein-free plasma into the tubular component

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24
Q

General Overview of Nephron Function

Efferent Arteriole

Generally Define Function

A

Carries blood from the glomerulus

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25
Q

General Overview of Nephron Function

Peritubular Capillaries

Generally Define Function

A

Supply the renal tissue
Involved in exchanges with the fluid in the tubular lumen

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26
Q

General Overview of Nephron Function

Juxtaglomerular Apparatus

Generally Define Function/Structure

A

Produces substances involved in the control of kidney function
Fluid proceeds to distal tubule
Specialized combo of tubular and vascular cells

Important in regulating blood pressue and GFR

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27
Q

General Overview of Nephron Function

Bowman’s Capsule

Generally Define Function

A

Collects the glomerular filtrate
Double walled cup like invagination

Increases surface area for diffusion

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28
Q

General Overview of Nephron Function

Proximal Tubule

Generally Define Function

A

uncontrolled reabsorption and secretion of selected substances occur here
Major site of reabsorption

Close to glomerulus

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29
Q

General Overview of Nephron Function

Loop of Henle

Generally Define Function

A

Establishes an osmotic gradient in the renal medulla that is important in the kidney’s ability to produce urine of varying concentration

Has an ascending and descending limb

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30
Q

General Overview of Nephron Function

Distal Tubule

Generally Define Function

A

Variable, controlled reabsorption of Na+ and H2O and secretion of K+ and H+ occur here

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31
Q

General Overview of Nephron Function

Collecting Duct

Generally Define Function

A

Variable controlled reabsorption of Na+ and H2O and secretion K+and H+ occur here
Fluid leaving the collecting duct is urine which enters the renal pelvis

Urine leaves for excretion

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32
Q

What are the two types of nephrons?

A

Cortical Nephrons
Juxtamedullary Nephrons

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33
Q

How are coritcal and juxtamedullary nephrons distinguished?

A

By their location and length of their structures

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34
Q

Define

Cortical Nephrons

Location, Structure, Function

A

Located mostly in cortex; extend just into outer medulla
Short loop of Henle
Surrounded by peritubular capillaries (continuation of EA, in the cortex)
Reabsorption and Secretion

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35
Q

Define

Juxtamedullary Nephrons

Location, Structure, Function

A

Extend deep into medulla
Long loop of Henle
Efferent arterioles form peritubular caps and vasa recta (continuation of EA, in the medulla)
Reabsorption, Secretion, Concentrate/dilute urine

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36
Q

Both types of nephrons are involved in…

Functions

A

Secretion and Reabsorption

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37
Q

Only the juxtamedullary nephron involves…

Functions

A

Concentration and dilution of urine

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38
Q

3 processes involved in urine formation

A

Glomerular Filtration
Tubular Reabsorption
Tubular Secretion

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39
Q

Define

Glomerular Filtration

What is it? Where does it go?

A

Pressure (primarily BP) leads to a seperation thru a semipermeable membrane
Found in Glomerulus -> fluid that is filtered into bowman’s capsule
Doesn’t contain cells or protein

“Pushing a portion of plasma onto a conveyor belt” (indiscriminate)

Cells and protein move through glomerulus to bowman’s capsule
Passive

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40
Q

Define

Tubular Reabsorption

What is it? Where does it go?

A

Fluid filtered into bowman’s capsule/Tubular Lumen is reabsorped into peritubular capillary
Selective
Moves substances back into blood flow
Unwanted substances remain in urine (Filtrate)

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41
Q

Define

Tubular Secretion

What is it? Where does it go?

A

Selectively adding substances from blood to filtrate
Mechanism for more rapidly eliminating selective substances
Peritubular Capillaries to Tubular Lumen

2nd chance for body to get rid of in urine

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42
Q

Ways substances can be filtered or rebasorbed

The substance is freely filtered and not reabsorped

What happens to the substance?

Substance ends up in urine

A

Filtration only

EX: Inulin

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43
Q

Ways substances are filtered and reabsorbed

The substance is freely filtered and partly reabsorbed

What happens to the substance?

A

Filtration, partial reabsorption

EX: Na+, K+, H2O

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44
Q

Ways substances are filtered and reabsorped

The substance is freely filtered and entirely reabsorbed

Substances you don’t want to lose

A

Filtration, Complete Reabsorption

EX: Glucose and Amino Acids

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45
Q

Ways substanes can be filtered and reabsorped

The substance is freely filtered and entirely secreted

Rarest; None returns to blood

A

Filtration, Secretion

Ex: Para-aminohippurate, PAH

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46
Q

Glomerular Filtration Barrier

3 layers of the Glomerular Filtration Barrier

A

Glomerular Capillary Wall (Endothelium)
Basement Mebrane
Inner Layer of Bowman’s Capsule (Epithelium)

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47
Q

Glomerular FIltration Barrier

Glomerular Capillary Wall

Structure, Function

A

Perforated by many Ig pores
100x more permeable than caps elsewhere in the body
endothelium has “-“ charge

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48
Q

Glomerular FIltration Barrier

What is the purpose of the negative charge on the Glomerular Capillary Wall and Basement Membrane?

A

Helps prevent negatively charged substances from getting through into the filtrate

Like proteins

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49
Q

Glomerular FIltration Barrier

Basement Membrane

Structure

A

Acellular gelatinous layer
composed of collagen and glycoproteins

Negatively Charged

50
Q

Glomerular Filtration Barrier

Inner Layer of Bowman’s Capsule

Function/Structure

A

Filtration slits between the podocyte processes that encircle the capillaries

Filtration slit diaphragm is composed of podocyn

51
Q

Glomerular FIltration Barrier

What is freely filtered through the Glomerular FIltration Barrier?

A

Water
Electrolytes
Molecules - MW less than 5,200

Small ions and molecules

52
Q

Glomerular FIltration Barrier

What is variably filtered through the Glomerular FIltration Barrier?

A

Molecules, including up to MW of ~68,000 - 69,000 depending on: Size, Shape, Charge

Long cylindrical filters better than spherical
Mid sized molecules

53
Q

Glomerular FIltration Barrier

What is not filtered through the Glomerular FIltration Barrier?

A

Larger Proteins

54
Q

Golmerular Filtration

What forces are involved in (drive) filtration across the glomerulus?

A

Starling Forces
Major force is Glomerular Capillary Hydrostatic Blood Pressure

Drives filtrate into Bowman’s Capsule

55
Q

Golmerular Filtration

What does Glomerular Capillary BP (Pg) depend on?

A

Arterial pressure
Afferent arteriole resistance
Efferent arteriole resistance

56
Q

Golmerular Filtration

Why do the afferent and efferent arteriole have a large effect on Glomerular Capillaries?

Why do the GC have a larger pressue than the the peritubular capillaries

A

Glomerular capillaries are located between the AA and EA, which results in them having a much higher pressure than the peritubular capillaries

57
Q

Golmerular Filtration

Why is a high glomerular pressure necessary?

A

To drive glomerular filtration

58
Q

Golmerular Filtration

Why is it necessary for peritubular capillaries to have a lower pressure?

A

To permit reabsorption of fluid from the renal interstitium

59
Q

Golmerular Filtration

Plasma-Colloid Pressure

Define

A

Unequal distribution of plasma proteins across the glomerular membrane not in bowman’s capsule

Water returns to the glomerulus

60
Q

Golmerular Filtration

What type of pressure is exerted by fluid in Bowman’s Capsule?

Define

A

Fluid in BC exerts a hydrostatic pressure

61
Q

Golmerular Filtration

What is the filtration force in Golmerular Filtration?

A

Golmerular Capillary Blood Pressure

62
Q

Golmerular Filtration

What are the opposing filtration forces in Golmerular Filtration?

A

Plasma-Colloid Osmotic Pressure + Bowman’s Capsule Hydrostatic Pressure

63
Q

Golmerular Filtration

A postive net filtration favors….

A

Filtration

64
Q

Golmerular Filtration

A negative net filtration favors…

A

Reabsorption

65
Q

Golmerular Filtration

What is the difference between net filtration along the glomerular capillaries vs. most capillaries in the body?

A

There is net filtration along the entire length of the glomerular capillaries

The opposing forces are still increasing but always less than Pgc
Oncotic pressure continues increasing along the capillary due to remaining proteins as everything else filters out

66
Q

What effect do changes in resistance of AA or EA have on blood flow? Why?

A

The have the same effect because they are in series

67
Q

Effect of changes in resistance on Renal Blood Flow (RBF) and GFR

At baseline, when resistance is the same in AA and EA…

In general, what happens to pressure

A

Pressure in GC = 60
AA and EA resistance = 1
Pressure in Peritubular Capillary = 20

68
Q

Effect of changes in resistance on Renal Blood Flow (RBF) and GFR

When the AA is constricted and the EA is not, what happens to GFR and RBF?

A

GFR and RBF both decrease
Pressure in GC = 40
AA resistance = 1.5
EA resistance = 1
Pressure in Peritubular Capillary = 13

69
Q

Effect of changes in resistance on Renal Blood Flow (RBF) and GFR

When the EA is constricted and the AA is not, what happens to GFR and RBF?

A

GFR increases and RBF decreases
Pressure in GC = 70
AA resistance = 1
EA resistance = 1.5
Pressure in Peritubular Capillary = 10

70
Q

Effect of changes in resistance on Renal Blood Flow (RBF) and GFR

When the AA is dilated and the EA is not, what happens to GFR and RBF?

A

GFR and RBF both increase
Pressure in GC = 70
AA resistance = 0.5
EA resistance = 1
Pressure in Peritubular Capillary = 30

71
Q

Effect of changes in resistance on Renal Blood Flow (RBF) and GFR

When the EA is dilated and the AA is not, what happens to GFR and RBF?

A

GFR decreases and RBF increases
Pressure in GC = 50
AA resistance = 1
EA resistance = 0.5
Pressure in Peritubular Capillary = 30

72
Q

Effect of changes in resistance on Renal Blood Flow (RBF) and GFR

Hydrostatic pressure in the glomerulus is controlled by….

A

Relative tone of afferent and efferent arterioles

73
Q

Define

Glomerular Filtration Rate (GFR)

A

The rate at which plasma is filtered (ml/min)
Index of Kidney Function

74
Q

What does GFR depend on?

A

Net filtration pressure
Surface area available for filtration
Membrane permeability

GFR = Kf x net filtration pressure

Kf = Surface area + membrane permeabiity

75
Q

What is the purpose of GFR?

What does it tell us?

A

GFR is an index of kidney function

Decrease in GFR can mean kidney disease
Increase GFR = Kidney recovery

76
Q

What is the advatange of a high GFR?

A

Rapid control of body fluid volume and composition

77
Q

What is used to measure GFR in clincial research? Why?

A

Inulin
It is the gold standard for measuring GFR

Inulin is the exogenous marker

78
Q

What is used to measure GFR in a patient? Why?

A

Creatinine
It is more convenient than inulin

Endogenous marker

79
Q

How is GFR measured?

A

We use the renal clearance of a substance that is freely filtered at the glomerulus, has a stable plasma concentration, is not reabsorbed, secreted, or metabolized by the kidney

Measured exogenously by inulin and endogenously by creatinine

80
Q

GFR

Inulin

Why is it the gold standard?

A

Filtered in the glomerulus, no tubular transport
But technically challenging and expensive

81
Q

GFR

Creatinine

What is it? Why is it used?

A

Derived from the skeletal muscle creatine
production proportional to muscle mass and is constant
plasma concentration is stable unless there are changes in production (decrease in malnutrition, increase in rhabdomyolysis), or changes in excretion (decreased in acute kidney injury)

Not gold standard because a small amount is secreted

82
Q

The amount of creatinine excreted per min =

A

amount of creatinine filtered per minute

83
Q

What is the relationship between GFR and plasma creatinine?

A

They are inversely related
Increasing GFR -> decreases creatinine

84
Q

Neurohumoral Control of GFR

What effects do the sympathetic nervous system have on GFR control?

A

Decreases RBF, Decreases GFR
Changes blood flow to kidneys
α1 activation -> vasoconstricton -> decreases BF -> decreases GFR
β1 activation -> renin release

vasoconstriction of afferent than efferent

85
Q

Neurohumoral Control of GFR

What effects does Angiotensin II have on GFR?

A

Decreases RBF, maintains GFR
Potent vasoconstrictor produced in response to descreases in AA pressure
AA and EA both constrict, EA more so

The larger constriction of EA allows GFR to be maintained

86
Q

Neurohumoral Control of GFR

What effects do Prostaglandins have on GFR?

A

Increase RBF, Increase GFR
PGE2 and PGI2 cause dilation of arterioles -> increases RBF, GFR

Effects afferent moreso than Efferent

Maintains GFR and RBF as we age due to increased production

87
Q

Equation

Blood flow through any organ is represented by…

A

Q = ΔP/R -> RBF = (Renal artery pressure - renal vein pressure)/ Renal vascular resistance (AA and EA)

Q = Blood Flow
ΔP = MAP - MVP
R = Resistance

88
Q

Kidneys regulate their BF by _ in response to changes in _.

A

Adjusting Resistance
Arterial Pressure

89
Q

Regulating GFR

What are the three ways GFR is regulated by changing RBF?

A

Autoregulation
Hormonal (Ang II, Prostaglandins)
SNS

90
Q

Regulation of GFR: Autoregulation

Autoregulation

What is its purpose? How does it work?

A

Feedback mechanisms intrinsic to the kidney
Operates to keep GFR steady over a wide range of blood pressure
Maintains BF over the range of 80-180

91
Q

Regulation of GFR: Autoregulation

What are the two types of autoregulation?

Both regulate AA tone

A

Myogenic Response
Tubuloglomerular Feedback

92
Q

Regulation of GFR: Autoregulation Mechanisms

Myogenic Response

Define

A

Fast-acting constriction/dilation to Δ in arterial pressure
Initiated in muscle
When AA is stretched (increase in wall tension), smooth muscle contracts

Pressure sensitive mechanism

Stretch of blood vessels allows Ca from ECF to enter cells and cause contraction
50% autoregulatory response

93
Q

Regulation of GFR: Autoregulation Mechanisms

Tubuloglomerular Feedback

Define

A

Complicated signals that respond to Δ in tubular fluid flow rate
Increase GFR -> Increase NaCl in filtrate/Juxtaglomerular apparatus -> Increase AA resistance -> decrease GFR

Flow dependent - Changes BF depending on Flow Rate through the nephrons

94
Q

Regulation of GFR: Autoregulation

What is the relationship between Arterial BP and GFR?

A

Arterial BP drives Glomerular Capillary pressure and thus GFR

Increase arterial BP -> increases GFR

95
Q

Regulation of GFR: Autoregulation

Where is the Juxtaglomerular Apparatus located?

A

Where the tubule passes through the fork of AA and EA at the glomerulus

96
Q

What is the structure of the JGA?

What makes it up?

A

Granular Cells
Extraglomerular Mesangial Cells
Macula Densa

97
Q

Juxtaglomerular Apparatus

Granular Cells

What are they? What do they?

A

Modified small muscle cells
Mechanoreceptors of the AA
Make, store, and secrete Renin

98
Q

Juxtaglomerular Apparatus

Extraglomerular mesangial cells

What are they? What do they?

A

Holds capillaries together
Full of actin for contraction
contraction closes portion of filtering capillaries -> decreases SA -> decreases GFR

99
Q

Juxtaglomerular Apparatus

Macula Densa

What is it? What does it do?

A

Chemoreceptors that detect NaCl
In contact with mesangial and granular cells

NaCl is proportional to rate of filtrate flow
Increase NaCl means Increase GFR -> AA constricts
Decrease NaCl means decrease GFR -> AA dilation

100
Q

What happens to GFR when NaCl increases?

During high flow rate

A

Increases in NaCl causes vasoconstriction and increases in GFR

↑ NaCl -> ATP -> Adenosine -> ↑ Ca -> contraction -> ↓ renin

101
Q

What happens to GFR when there is Low flow rate?

A

↓Arterial Pressure → ↓Glomerular Hydrostatic Pressure → ↓GFR → ↓Macula Densa/NaCl → ↑ Renin → ↑ Ang II → ↑EA resistance → inhibits ↓Glomerular Hydrostatic Pressure → ↑GFR

↓Arterial Pressure → ↓Glomerular Hydrostatic Pressure → ↓GFR → ↓Macula Densa/NaCl → ↓ AA resistance → inhibits ↓Glomerular Hydrostatic Pressure → ↑GFR

102
Q

3 most important points concerning Autoregulation

Autoregulation is absent when…

A

Arterial BP is < 80 mmHg

103
Q

3 most important points concerning Autoregulation

Despite autoregulation, the RBF and GFR can be changed by…

General

A

Certain hormones and changes in sympathetic nerve activity

104
Q

3 most important points concerning Autoregulation

Autoregulation of GFR and RBF provides an effective means for…which ensures…

A

Autoregulation of GFR and RBF provides an effective means for uncoupling renal function from arterial pressure thus ensuring fluid and solute excretion remain constant

105
Q

GFR

What can override renal autoregulation?

A

Sympathetic Nervous System

106
Q

Extrinsic Sympathetic Control on GFR

Strong activation of renal sympathetic nerves can _ renal arterioles and _ RBF and GFR

A

Strong activation of renal sympathetic nerves can constrict renal arterioles and ↓ RBF and GFR

107
Q

Extrinsic Sympathetic Control on GFR

What effect does SNS have on renin and overall GFR?

A

↑ Renin → RAA →↑Na+ reabsorption (PT)

108
Q

What would happen to GFR during a hemorrhage?

A

Hemorrhage →↓ECF Volume → ↓MAP → ↑SNS activation → ↓GFR

↓MAP - detected by carotid baroreceptors
↑SNS activation - Input to Afferent Arteriole (constriction)

109
Q

Why would GFR need to be decreased?

A

Decrease GFR to hold onto important things

110
Q

Pathway of fluid flow

What is the sequence of fluid flow through the kidneys?

General Overview

A

Kidney → Renal Pelvis → Ureter → Bladder → Urethra

111
Q

Pathway of fluid flow

What is the sequence of fluid flow through the arterial portion of the renal system?

A

Renal Artery → Afferent Arteriole → Glomerulus → Efferent Arteriole → Peritubular Capillaries → Renal Vein

112
Q

Pathway of fluid flow

What is the sequence of fluid flow through the filtrate pathway of the renal system?

A

Glomerulus → Bowman’s Capsule → Proximal Tubule → Loop of Henle → Distal Tubule → Collecting Duct

113
Q

Which of the following would cause the greatest decrease in GFR in a person with otherwise normal kidneys?
A. Decrease in renal pressure from 100 to 80 mmHg in normal kidney
B. 50% increase in glomerular capillary filtration coefficient
C. 5 mmHg increase in glomerular capillary blood pressure
D. 50% decrease in afferent arteriolar resistance
E. 50% decrease in efferent arteriolar resistance
F. 5 mmHg decrease in Bowman’s Capsule pressure

A

E. 50% decrease in efferent arteriolar resistance

Vasodilation of EA → ↓ GFR

114
Q

Would GFR increase or decrease if there is…

A rise in Bowman’s Capsule pressure resulting from ureteral obstruction by a kidney stone

A

decrease

115
Q

Would GFR increase or decrease if there is…

A fall in plasma protein resulting from loss of these proteins from a large burned surface

A

Increase

116
Q

Would GFR increase or decrease if there is…

A dramatic fall in arterial blood pressure following severe hemorhage (<80 mmHg)

A

Decrease

117
Q

Would GFR increase or decrease if there is…

Afferent Arteriolar vasoconstriction

A

Decrease

118
Q

Would GFR increase or decrease if there is…

Tubuloglomerular feedback response to a decrease in tubular flow rate

A

Increase

119
Q

Would GFR increase or decrease if there is…

Myogenic response of an afferent arteriole stretched as a result of an increased driving BP

A

Decrease

120
Q

Would GFR increase or decrease if there is…

Sympathetic activity to the afferent arterioles

A

Decrease

121
Q

Would GFR increase or decrease if there is…

Contraction of the mesangial cells

A

Decrease

122
Q

Would GFR increase or decrease if there is…

Contraction of the podocytes

A

Decrease

2023 Systems Phys (41 decks)

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