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Physiology 210 > Renal Physiology > Flashcards

Renal Physiology Flashcards

1
Q

What are the functions of the kidneys?

A

Regulates blood volume and pressure
Maintaining pH
Excrete urea, uric acid, creatinine, bilirubin, and removal of foreign chemicals
Synthesizes glucose
Secretes EPO, renin, and 1,25-dihydroxy Vitamin D

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2
Q

Why do fluid volume changes occur?

A

During various health disorders

By rapid movement of water (osmosis)

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3
Q

Where is 40% of the body’s water content found?

A

Intracellular fluid

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4
Q

Where is 20% of the body’s water content found?

A

Interstitial fluid

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5
Q

What fluid compartment do the kidneys regulate?

A

Extracellular fluid

  • fluid outside of cell
  • plasma
  • interstitial fluid
  • CSF
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6
Q

What fluid compartment is [Na+] higher?

A

Extracellular fluid compartment

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7
Q

What fluid compartment is [K+] higher?

A

Intracellular fluid compartment

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8
Q

What fluid compartment is [Cl-] higher?

A

Extracellular fluid compartment

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9
Q

What fluid compartment is [HCO3-] higher?

A

Extracellular fluid compartment

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10
Q

What fluid compartment is [PO4-] higher?

A

Intracellular fluid compartment

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11
Q

What are aquaporins?

A

Water channels

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12
Q

What is water concentration measured in?

A

Osmoles = 1 osm is equal to 1 mole of solute particles

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13
Q

What is osmolarity?

A

Number of solutes per unit volume of solution expressed in moles per litre

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14
Q

What is the water concentration when there is low osmolarity?

A

High water concentration

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15
Q

What is the water concentration when there is high osmolarity?

A

Low water concentration

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16
Q

What is osmosis?

A

Net diffusion of water across a selectively permeable membrane from a region of high water concentration to one with a lower water concentration

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17
Q

What is osmotic pressure?

A

The pressure necessary to prevent solvent movement (osmosis)

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18
Q

What is tonicity?

A

Determined by the concentration of non-penetrating solutes of an extracellular solution relative to the intracellular environment of the cell
The solute concentration may influence changes in cell volume

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19
Q

What does isotonic mean?

A

Same osmolarity inside and outside of the cell

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20
Q

What does hypertonic mean?

A

Higher osmolarity outside than inside of the cell

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21
Q

What does hypotonic mean?

A

Lower osmolarity outside than inside of the cell

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22
Q

Which way does water flow?

A

From low osmolarity to high osmolarity

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23
Q

What is absorption?

A

Movement of solute/water into the blood (plasma)

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24
Q

What is filtration?

A

Movement of solute/water out of the blood (plasma)

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25
Q

What happens when the net filtration is positive?

A

Favours filtration

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26
Q

What happens when the net filtration is negative?

A

Favours absorption

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27
Q

What is homeostasis?

A

The total body balance of any substance

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28
Q

What are the associated organs in the urinary system?

A

Ureters
Bladder
Urethra

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29
Q

Where is the location of the kidneys?

A

Retroperitoneal

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30
Q

What is the function of the ureters?

A

Drain the formed urine from the kidneys and empty it into the bladder

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31
Q

What is the function of the bladder?

A

Stores urine and empties out of the body via the urethra

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32
Q

What is micturition?

A

Urination

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33
Q

What is the nephron?

A

The functional unit of the kidneys

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34
Q

What are the parts of the nephron?

A

Renal Corpuscle

Renal tubule

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35
Q

What is the renal corpuscle composed of?

A

Glomerulus

Bowman’s capsule

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36
Q

What are the parts of the renal tubule?

A

Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting ducts

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37
Q

What is the proximal convoluted tubule?

A

Close to the renal corpuscle

Twisted

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38
Q

What is the loop of Henle?

A

Divided into the descending limb and ascending limb

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39
Q

What is the distal convoluted tubule?

A

Far away from the renal corpuscle

Drains its contents into the main tube called the collecting duct

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40
Q

What is the collecting duct?

A

Nephrons drain into the collecting ducts which collect all formed processed contents and empty into the renal pelvis of the kidney

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41
Q

What does the renal corpuscle do?

A

The initial blood filtering component

Blood enters from the afferent arteriole and leaves through the efferent arteriole

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42
Q

What does Bowman’s capsule do?

A

The filtrate enters Bowman’s space once the blood has been filtered
Has podocytes that come in contact with the glomerulus
Has epithelial cell layer that continues on to form the tubule

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43
Q

How is the renal corpuscle developed?

A

Step 1: nephrons develop as blind-ended tubules composed of a single layer of simple epithelium

Step 2: A growing tuft of capillaries penetrate the expanded end of the tubules
-epithelial layer differentiates into the parietal and visceral layers

Step 3: Parietal layer eventually flattens to become the wall of Bowman’s capsule, the visceral layer becomes podocyte layer

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44
Q

What are the 3 layers of the glomerular capillary?

A

Endothelial layer
Basement membrane
Podocytes with filtration slits

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45
Q

Where are all renal corpuscles found?

A

In the cortex

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46
Q

What are the two types of nephrons?

A

Cortical

Juxtamedullary

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47
Q

What are cortical nephrons?

A

Do basic functions (filtration, reabsorption, secretion)

Most of the nephron is found in the cortex

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48
Q

What are juxtamedullary nephrons?

A

Do basic functions, regulate the concentration of urine
The renal corpuscle is found in the cortex closer to the medulla, the loop of Henle and the ascending limb are found in the renal medulla

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49
Q

What are the 3 types of capillaries around the nephron?

A

Glomerular
Peritubular
Vasa recta

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50
Q

Where are vasa recta capillaries found?

A

Mostly associated with juxtamedullary nephrons in the medullary portion of the kidney

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51
Q

What are the 3 basic renal processes?

A

Glomerular filtration
Tubular secretion
Tubular reabsorption

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52
Q

What is glomerular filtration?

A

Fluid in the blood is filtered across the capillaries of the glomerulus and into Bowman’s space

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53
Q

What is tubular reabsorption?

A

The movement of a substance from inside the tubule into the blood

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54
Q

What is tubular secretion?

A

Movement of nonfiltered substances from the capillaries into the tubular lumen

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55
Q

What is the amount excreted equal to?

A

Amount filtered + amount secreted - amount reabsorbed

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56
Q

What can’t move out of the glomerular capillaries into Bowman’s space

A

Large proteins and albumin
Why?
pores are not large enough and the pores and basement membrane have negative charges and repel negatively charged proteins

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57
Q

What is filtered through the glomerulus?

A

Water, electrolytes, glucose, amino acids, fatty acids, vitamins, waste products (urea, uric acid, creatinine)

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58
Q

What is ultrafiltrate?

A

The concentration of substrate filtered through the filtration layers is the same in plasma and in the filtrate
cell-free fluid

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59
Q

What is proteinuria?

A

A condition where some of the proteins that are not supposed to pass through the filtration barrier show up in the filtrate and ultimately in the urine

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60
Q

Is the net glomerular filtration pressure always positive or negative?

A

Positive

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61
Q

How does glomerular filtration pressure initiate urine formation?

A

By forcing protein-free filtrate from plasma out of the glomerulus and into Bowman’s space

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62
Q

What forces favour filtration?

A

Glomerular capillary blood pressure

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63
Q

What forces oppose filtration?

A

Fluid pressure in Bowman’s space

Osmotic force due to protein in plasma

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64
Q

What factor would contribute to an increase in the glomerular filtration rate?

A

High blood pressure

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65
Q

What factor would contribute to a decrease in the glomerular filtration rate?

A

An increase in the protein concentration in the plasma would increase the protein content in the glomerular capillaries, decreasing the glomerular filtration rate

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66
Q

What is the fraction of the volume entering the glomerular capillaries that are filtered?

A

20%

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67
Q

What is the final volume of fluid that is excreted?

A

1%

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68
Q

What is the definition of glomerular filtration rate?

A

The volume of fluid filtered from the glomerulus into the Bowman’s space per unit time

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69
Q

How much GF happens per day?

A

180 L/day

Rate is not fixed

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70
Q

What are some factors influencing GFR?

A

Net glomerular filtration pressure
Neural and endocrine control
Permeability of the corpuscular membrane
Surface area available for filtration

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71
Q

What is GFR autoregulation?

A

GFR remains fairly constant despite large changes in arterial pressure or renal blood flow
Regulated by changes in the myogenic reflex
Occurs by changing renal blood vessel resistance to compensate for any changes in pressure

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72
Q

How is a constant GFR rate maintained?

A

Autoregulation of GFR takes place over a wide range of blood pressures

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73
Q

How does constriction of the afferent arteriole affect the GFR?

A

Constriction increases resistance to flow through the afferent arteriole
Renal blood flow to the glomerulus has decreased due to an increase in the resistance in the afferent arteriole
A decrease in renal blood flow reduces the hydrostatic pressure of the glomerular capillary resulting in a decrease in GFR

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74
Q

What are the 4 scenarios that alter GFR?

A

Constrict afferent arterioles
Constrict efferent arterioles
Dilate efferent arterioles
Dilate afferent arterioles

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75
Q

What 2 scenarios decrease GFR?

A

Constricting the afferent arteriole

Dilating the efferent arteriole

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76
Q

What 2 scenarios increase GFR?

A

Constricting the efferent arteriole

Dilating the afferent arteriole

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77
Q

How is GFR regulated?

A

Myogenic response
Hormones and autonomic neurons
Tubuloglomerular feedback

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78
Q

What is the juxtaglomerular apparatus?

A

A specialized structure formed by the distal convoluted tubule and the glomerular afferent arteriole

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79
Q

What are the 3 types of cells that control the GFR?

A

Macula densa
Juxtaglomerular cells
Mesangial cells

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80
Q

What is the macula densa?

A

Cells on the wall of the distal tubule
Can sense increase fluid flow through the distal tubule
Secretes vasoactive compounds
Changes afferent arteriole resistance and signals to JG cells

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81
Q

What are juxtaglomerular cells?

A

On the wall of the afferent arteriole

Secrete renin which controls afferent arteriole resistance

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82
Q

What are the mesangial cells?

A

Not part of the JGA

Contraction of these cells reduces surface area of the glomerular capillaries so GFR is reduced

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83
Q

What is the filtered load?

A

The total amount of non-protein or non-protein bound substance filtered into Bowman’s space

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84
Q

What is the filtered load equation?

A

GFR x [substance in plasma]

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85
Q

What happens when the substance excreted in urine is less than the filtered load?

A

Reabsorption occurs

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86
Q

What happens when the substance excreted in urine is greater than the filtered load

A

Secretion occurs

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87
Q

What are the 3 ways that the renal system handles different substances?

A

Filtration + secretion
Filtration + partial reabsorption
Filtration + complete reabsorption

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88
Q

How are inulin and creatinine handled by the renal system?

A

Filtration only - what is filtered is excreted completely in the urine
No secretion or reabsorption

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89
Q

How are electrolytes handled by the renal system?

A

Filtered and partially reabsorbed

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90
Q

How are glucose and amino acids handled by the renal system?

A

Filtered and completely reabsorbed

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91
Q

How are organic acids and bases handled by the renal system?

A

Filtered and secreted

The substance is completely secreted in urine

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92
Q

What percent of water is reabsorbed every day?

A

99%

93
Q

What percent of sodium is reabsorbed every day?

A

99.5%

94
Q

What percent of glucose is reabsorbed every day?

A

100%

95
Q

What percent of urea is reabsorbed every day?

A

44%

96
Q

What is reabsorption mediated by?

A 
Diffusion across tight junction (paracellular) = minor 
Mediated transport (transepithelial) = major
97
Q

What is the pathway of transepithelial transport for the reabsorption of sodium?

A

Across luminal or apical membrane

Across basolateral membrane

98
Q

How do sodium move across the apical side and the basolateral membrane?

A 
Apical = passive diffusion 
Basolateral = active transport on basolateral membrane by Na+/K+ ATPase
99
Q

How is sodium reabsorbed?

A

Sodium enters the cell through membrane proteins moving down its electrochemical gradient
Sodium is then pumped out of the basolateral side of the cell by the Na+/K+ ATPase

100
Q

How is glucose reabsorbed?

A

Sodium moving down its electrochemical gradient using the SGLT protein pulls glucose into the cell against its concentration gradient
Glucose diffuses out of the basolateral side of the cell using the GLUT protein
Sodium is pumped out by Na+/K+ ATPase

101
Q

What is glucose reabsorption linked to?

A

Sodium-linked glucose reabsorption in the proximal tubule

102
Q

What is glucosuria?

A

When above threshold glucose appears in the urine

103
Q

What is the transport maximum?

A

Limit of substance that can be transported per unit time
Binding sites of transport proteins become saturated
Filtered load exceeds the limit of reabsorption

104
Q

What is diabetes mellitus?

A

The capacity to reabsorb glucose is normal, but the filtered load is greatly increased and is beyond the threshold level to reabsorb glucose by the tubules

105
Q

What is renal glucosuria?

A

Genetic mutation of the Na+/glucose cotransporter, which normally mediates active reabsorption of glucose in the proximal tubules

106
Q

What is urea reabsorption dependent on?

A

Water reabsorption

107
Q

What is urea reabsorbed?

A

Water reabsorption occurs in the proximal tubule
The concentration of urea increases inside the tubular lumen
Urea diffuses down the concentration gradient

108
Q

What is tubular secretion?

A

Involves active transport
Tubular secretion is also coupled to the reabsorption of Na+
Mostly H+ and K+, also choline creatinine and penicillin

109
Q

What is renal clearance?

A

A way of quantifying kidney function in removing substances from the plasma
The measure of the volume of plasma from which a substance is completely removed by the kidney/unit time
Clearance of S = Mass of S excreted per unit time / plasma concentration of S

110
Q

How is inulin cleared?

A

Readily filtered but not reabsorbed, secreted, or metabolized by the tubule
Can be used to measure GFR

111
Q

How is creatinine cleared?

A

Product of muscle metabolism
Filtered, not absorbed, but undergoes slight secretion
Clearance of creatinine slightly overestimates GFR but can be used clinically

112
Q

What must happen if the clearance of substance X is greater than GFR?

A

X must undergo secretion

113
Q

What must happen if the clearance of substance X is less than GFR?

A

X must undergo reabsorption

114
Q

How is sodium transported in the nephron?

A

Actively reabsorbed

115
Q

How is chloride transported in the nephron?

A

Transported passively when sodium is pumped out of the cell

116
Q

How is potassium transported in the nephron?

A

Secreted into the tubules mainly by cells of the distal and collecting ducts

117
Q

What labour does the proximal convoluted tubule do?

A

Reabsorbs majority of the water and non-waste plasma solutes
The major site of solute secretion, except potassium

118
Q

What labour does the loop of Henle do?

A

Creates an osmotic gradient in the interstitial space

119
Q

What labour does the distal convoluted tubule do?

A

Site of major physiological control for water reabsorption

Major homeostatic mechanisms of fine control of water and solute to produce urine

120
Q

What is reabsorbed and secreted?

A

Proximal tubules = 80% reabsorptive and secretory activities

Loop of Henle = little water, but large amounts of ions are reabsorbed

Distal tubules = 12-15% reabsorption happens here

121
Q

What are sources of water gain?

A

Ingested liquid

Water from oxidation of food

122
Q

What are some avenues of water loss?

A

Skin, respiratory airways
Sweat
GI tract, urinary tract, menstrual flow

123
Q

What is water absorption dependent on?

A

Na+ reabsorption

The osmotic gradient set up by Na+ reabsorption acts as the driving force

124
Q

Which hormone regulates water reabsorption?

A

Vasopressin or antidiuretic hormone

125
Q

What does vasopressin regulate?

A

A specific type of aquaporin

126
Q

Where in the tubule does vasopressin regulation occur?

A

In the collecting ducts

127
Q

Does the distal tubule reabsorb water?

A

No, there are no aquaporins

128
Q

What does the thin descending portion of the loop of Henle reabsorb?

A

Water

129
Q

What does the thick ascending portion of the loop of Henle reabsorb?

A

Salt, the ascending limb is impermeable to water

130
Q

What are the structure-function relationships of the loop of Henle?

A

A single tubule with two sides closely juxtaposed

Fluid streams in the opposite directions and different transport capabilities of each side of the tubule

131
Q

How is the hyperosmolar interstitial fluid in the renal medulla generated?

A

The ascending limb actively transports NaCl into the interstitial fluid and is impermeable to water
The result is a gradient difference of 200 mOsm

132
Q

What is happening in the descending loop of Henle?

A

A net movement of water occurs out of the descending limb and the ascending limb continues to actively pump out solute

133
Q

What is the counter-current multiplier?

A

Multiplication of the gradient down the length of the loop of Henle

134
Q

How is the fluid that flows along the tube?

A

The fluid becomes concentrated in the descending limb

Dilutes fluid again as it climbs up the ascending limb and enters the distal tubule

135
Q

What happens to the fluid at the collecting duct?

A

ADH works on the collecting duct and the fluid inside the tubule becomes isoosmotic with the interstitial space
More water is reabsorbed from the cortical collecting due to the ADH effect
The high osmolarity that is established in the interstitial space helps the water to permeate out of the medullary collecting tubule

136
Q

What does a short loop mean?

A

Does not need to conserve water

137
Q

What does a long loop mean?

A

Needs to conserve more water

138
Q

What is the vasa recta?

A

Blood vessels that run parallel to the loop of Henle

139
Q

What is counter-current blood flow?

A

Blood flows through in one direction and goes out the other direction

140
Q

Why is the hyperosmotic interstitial gradient created?

A

To absorb water into the interstitial space

141
Q

What are the nephrons that create the gradient?

A

Juxtamedullary nephrons

142
Q

How does blood in the vasa recta flow as compared to how fluid flows in the loop of Henle?

A

Opposite directions

143
Q

What is the vasa recta permeable to?

A

Both solute and water

144
Q

What are 3 ways that the vasa recta helps countercurrent exchange?

A
  1. Blood flow in the vasa recta serves as countercurrent exchangers
    - helps in maintaining the Na+ and the Cl- gradient
    - gradient is not washed away
  2. Blood flow is the medulla is low
    - less than 5% of the trial renal blood flow and is sluggish
    - prevents solute loss
  3. The capillaries are freely permeable to ions, urea, and water, and they move in and out of the capillaries in response to the concentration gradients
    - vasa recta does not create medullary hyperosmolarity, but prevents it from being washed out, and therefore maintains it
145
Q

What is the countercurrent exchange of the vasa recta?

A

NaCl moves out of the ascending limb, interstitium, to enter the descending limb as blood enters the descending limb of the vasa recta
Water diffuses out of the descending limb into the ascending limb
This mechanism reinforces the gradient created by renal tubules by the exchange of salt and water which leads to an increase in sodium and urea concentration in the renal medulla interstitial space

146
Q

How much urea is excreted?

A

Only 15% of the original amount

147
Q

What helps maintain high osmolarity in the medulla?

A

Minimal uptake of urea by vasa recta and recycling urea in the interstitial space

148
Q

Why is there a need for concentrated urine?

A

Kidneys save water by producing hyperosmotic urine

149
Q

What are the mechanisms used to maintain the hyperosmotic environment of the medulla?

A
  1. Counter-current anatomy and opposing fluid flow through the loop of Henle of the juxtamedullary nephrons
  2. Reabsorption of NaCl in ascending limb
  3. Impermeability of ascending limb to water
  4. Trapping of urea in the medulla
  5. Hairpin loops of vasa recta maintains the hyperosmotic interstitium in the medulla
150
Q

What do changes in total body [Na+] cause?

A

Changes in blood volume and blood pressure

151
Q

What is blood osmolarity determined by?

A

Measuring the plasma [Na+]

152
Q

What does the volume of water reabsorption dictate?

A

How much water will be excreted

153
Q

What exerts physiological control of water reabsorption and excretion?

A

ADH (vasopressin)

154
Q

What is the site of action of vasopressin?

A

Collecting duct cells

155
Q

What is the mechanism of action of vasopressin?

A

Alters water permeability of the luminal membrane of the collecting duct cells

156
Q

Where is vasopressin made and secreted?

A

Produced by cells of the SON of the hypothalamus

Secreted by the posterior pituitary

157
Q

Where are aquaporins 2,3,4 located?

A

Collecting ducts

158
Q

What is aquaporin 2 insertion on the luminal side regulated by?

A

ADH (vasopressin) via AQP2 gene transcription

159
Q

What is the mechanism of ADH action?

A

ADH binds to a receptor on the cell and through G-protein coupled mechanism, transcription factors are activated and AQP-2 is up-regulated
Water moves across the apical membrane through AQP-2 and out of the basolateral membrane through AQP-3 and 4
AQP-2 is under the control of ADH but the others are not

160
Q

What happens if ADH levels are really low?

A

AQP-2 channels will be recycled or taken back by endocytosis

161
Q

What happens in the absence of ADH?

A

Collecting ducts cells are almost impermeable to water

Extreme loss of large fluid = water diuresis

162
Q

What is central diabetes insipidus?

A

Failure to release ADH from the posterior pituitary

163
Q

What is nephrogenic diabetes insipidus

A

ADH is secreted by doesn’t function right

164
Q

When is ADH increased (pee less)?

A

Shock, pain, warm, hot weather, and water deprivation

165
Q

When is ADH decrease (pee more)?

A

Cold, humid environment, alcohol

166
Q

What is the relationship between water deprivation and thirst?

A

Water deprivation leads to high plasma osmolarity which stimulates hypothalamic osmoreceptors
This increases ADH release which leads to thirst and water intake as well as renal water retention and antidiuresis

167
Q

What is the relationship between water intake and thirst?

A

Water intake leads to low plasma osmolarity which blocks hypothalamic osmoreceptors
This blocks ADH and leads to renal water excretion and large water diuresis

168
Q

What is water diuresis?

A

Only excess water is excreted without excess solute in urine

169
Q

What is osmotic diuresis?

A

Excess solute in urine is always associated with high levels of water excretion
Uncontrolled diabetes mellitus

170
Q

Is sodium ever secreted into the renal tubes?

A

No, never

171
Q

What is the short-term regulation of low sodium in the plasma?

A

Baroreceptors regulate GFR

172
Q

What is the long-term regulation of low sodium in the plasma?

A

Aldosterone facilitates Na+ reabsorption

Renin and angiotensin II are needed

173
Q

What is the regulation of high sodium in the plasma?

A

Atrial natriuretic peptide
ANP regulates GFR and inhibits Na+ reabsorption
ANP also works by inhibiting aldosterone actions

174
Q

What are baroreceptors

A

Used for short-term regulation of low plasma volume, nerve endings sensitive to tough

175
Q

Where are the baroreceptors located?

A

Carotid sinus, aortic arch, major veins, intrarenal (JG cells of JGA)

176
Q

How do baroreceptors work?

A

Can sense changes in blood volume and peripheral resistance
Increase or decrease in blood pressure causes an increase or decrease in stretch which causes an increases or decrease in nerve impulse frequency

177
Q

Where is baroreceptor information processed?

A

In the medulla oblongata

Activation of the ANS

178
Q

What is the role of baroreceptors in plasma (Na+)?

A

When there is low Na+, there is low plasma volume, which means low arterial blood pressure and reduced firing of baroreceptors
This increases the activity of sympathetic renal nerves and increased afferent arteriolar constriction which decreased GFR and increases Na+ reabsorption

179
Q

What is aldosterone?

A

A steroid hormone secreted from the adrenal cortex
Low plasma volume associated with low sodium triggers its release
Regulates Na+ reabsorption
Effect is long-term

180
Q

What is the site of action of aldosterone?

A

Late distal tube and cortical collecting duct

181
Q

What is the action of aldosterone?

A

Induces the synthesis of Na+ transport proteins
Stimulates Na+ reabsorption
Reduces Na+ excretion

182
Q

What regulates aldosterone secretion?

A

Na+ content in diet

High Na+ intake = low aldosterone secretion
Low Na+ intake = high aldosterone secretion

183
Q

How does angiotensin II relate to aldosterone?

A

Acts on the adrenal cortex to control the secretion of aldosterone

184
Q

What is renin?

A

An enzyme that is a sensor for low NaCl in the blood and converts angiotensin to angiotensin I

185
Q

What is ACE?

A

Angiotensin converting enzyme

Converts angiotensin I to angiotensin II

186
Q

What is an ACE inhibitor?

A

Drug to manage high blood pressure by blocking the ACE enzyme

187
Q

Where is renin secreted?

A

From the juxtaglomerular cells of the JGA

188
Q

What is the most important trigger for the release of aldosterone?

A

The renin-angiotensin mechanism

189
Q

What does the renin-angiotensin mechanism respond to?

A

Sympathetic stimulation of renal nerves
Decrease in filtrate osmolarity
Decreased blood pressure

190
Q

What do the juxtaglomerular cells do?

A

Mechanoreceptors
Sense circulating plasma volume
Secrete renin

191
Q

What determines [renin] in the plasma?

A

Sympathetic input from external baroreceptors
Intrarenal baroreceptors
Signals from the macula densa

192
Q

What is the macula densa?

A

On the wall of the distal convoluted tube
Chemoreceptors
Sense NaCl load of the filtrate

193
Q

Where is ANP made?

A

Synthesized and secreted by the cardiac atria

194
Q

What is the site of ANP action?

A

On cells of several tubular segments
ANP inhibits aldosterone
Inhibits Na+ reabsorption
Increases GFR and Na+ excretion

195
Q

What stimulates ANP secretion?

A

Increased Na+ concentration
Increased blood volume
Arterial distension

196
Q

What is the amount of K+ excreted?

A

K+ filtered - K+ absorbed + K+ secreted

197
Q

Where is most of filtered K+ reabsorbed?

A

In the proximal tubule and the loop of Henle

198
Q

Where can K+ be secreted?

A

The collecting duct

199
Q

What is [K+] in the urine regulated by?

A

The cortical collecting duct

200
Q

What is hyperkalemia?

A

Excess K+ in the blood

201
Q

What controls the homeostasis of K+ in the body?

A

Aldosterone secreting cells in the adrenal cortex are sensitive to extracellular [K+]

202
Q

What happens when there is an increase in extracellular [K+]?

A

Stimulation of aldosterone production so more K+ is excreted in the urine

203
Q

What happens when there is a decrease in extracellular [K+]?

A

No aldosterone is produced so less K+ is excreted in the urine

204
Q

Can aldosterone stimulate K+ secretion?

A

Yes, it stimulates both Na+ reabsorption and K+ secretion in the cortical collecting duct

205
Q

What can small changes in pH do to enzymes?

A

Cause proteins to change shape

  • alter their activity
  • changes in neuronal activity
  • coupled to K+ imbalances
  • irregular cardiac beats
206
Q

What is an acid?

A

Releases protons into the solution

207
Q

What is a base?

A

Accepts protons in a solution

208
Q

What is an example of a volatile acid?

A

Carbon dioxide

209
Q

What are some nonvolatile acids?

A

Organic and inorganic acids other than CO2
Phosphoric acid
Sulfuric acid

210
Q

What acid does the metabolism of sulfur-containing amino acids produce?

A

Sulfuric acid

211
Q

What does the metabolism of lysine, arginine, and histidine produce?

A

Hydrochloric acid

212
Q

What is a buffer?

A

Any substance that binds to H+
Composed of a weak acid and its conjugate base
Buffers modify or adjust the change in pH following the addition of acids or bases

213
Q

What are the types of buffers?

A

Most of the H+ are buffered by extracellular or intracellular fluid
CO2/HCO3- is the extracellular buffer system
Phosphate ions and proteins are intracellular buffers (like hemoglobin)

214
Q

What is the role of kidneys and lungs in acid base balance?

A

Both responsible for balancing hydrogen ion concentration within a narrow range

215
Q

What homeostatic role do the lungs play?

A

Short-term

216
Q

What causes respiratory imbalances?

A

Hyperventilation
Hypoventilation
Respiratory malfunction

217
Q

What happens if the imbalance is non-respiratory?

A

Ventilation is changed by reflex to adjust the balance

  • increased proton concentration stimulates ventilation
  • decreased proton concentration inhibits ventilation
218
Q

What homeostatic role do the kidneys play?

A

Long-term

Ultimate balancers

219
Q

What is the key concept about the relationship between H+ and HCO3-?

A

When 1 H+ ion is lost from the body, 1 HCO3- is gained by the body

220
Q

What happens during alkalosis?

A

There is decreased plasma [H+]
The kidneys excrete more bicarbonate
Results in restoration of the acid-base balance

221
Q

What happens during acidosis?

A

There is increased plasma [H+]
The kidney cells synthesize new bicarbonate and send it to the blood
Results in restoration of acid-base balance

222
Q

How is HCO3- reabsorbed?

A

Dependent on H+ secretion and is an active process
normally most of the HCO3- is reabsorbed
Occurs in the proximal tubule, ascending loop of Henle, and cortical collecting duct
The transport mechanism is different depending on the segment

223
Q

What is mechanism 1 of the addition of HCO3- to the plasma?

A

Response to acidosis
When more H+ is secreted than there is HCO3- in the lumen to bind the H+
Extra H+ binds to HPO4-
HCO3- is still generated by tubular cells and diffuses into plasma
The new gain of HCO3- in the plasma

224
Q

What is mechanism 2 of the addition of HCO3- to the plasma?

A

Cells from the proximal tubule are only involved
Uptake of glutamine from glomerular filtrate or peritubular plasma
NH4+ and HCO3 are formed inside the cells
NH4+ is actively secreted via the Na+/NH4+ counter transport into the lumen
HCO3- is added to the plasma

225
Q

What is respiratory acidosis?

A

Occurs as a result of decreased ventilation
Increased blood PCO2
Occurs in emphysema
Kidney compensates by secreting H+ and lowers plasma [H+]

226
Q

What is respiratory alkalosis?

A

Occurs as a result of hyperventilation
Decreased blood PCO2
Happens in high altitude
Kidney compensates by excreting HCO3-

227
Q

What is metabolic acidosis?

A 
Occurs in diarrhea 
Severe exercise 
Diabetes mellitus 
Results in increased ventilation 
Results in increased H+ secretion
228
Q

what is metabolic alkalosis?

A

Occurs after prolonged vomiting
Results in decreased ventilation
Results in increased HCO3- excretion

Physiology 210 (12 decks)

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