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SP1 Physiology/Microanatomy 2 > Lecture 33 4/5/24 > Flashcards

Lecture 33 4/5/24 Flashcards

1
Q

What are the main functions of the kidney?

A

-control blood volume and electrolyte composition
-renin-angiotensin II pathway
-rid body of waste material
-acid-base regulation
-regulation of erythrocyte production
-regulation of calcitriol production
-glucose synthesis

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2
Q

What does the rate of glomerular filtration depend on?

A

-rate of kidney blood flow
-properties of the glomerular capillary membranes

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3
Q

How does urine formation begin?

A

large amount of fluid that is virtually protein-free is filtered from glomerular capillaries into Bowman’s capsule

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4
Q

What is the concentration of glomerular filtrate in Bowman’s capsule similar to?

A

plasma

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5
Q

What happens to the filtrate as it passes from Bowman’s capsule through the tubules?

A

-modified by reabsorption of water and specific solutes into the blood
-modified by secretion of substances from peritubular capillaries into the tubules

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6
Q

What is net excretion the result of?

A

what is filtered - what is reabsorbed + what is secreted

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7
Q

How does filtration impact reabsorption?

A

increased filtration leads to increased reabsorption

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8
Q

What are the types of filtration and reabsorption patterns in the kidney?

A

-filtration only: creatinine
-filtration and complete reabsorption: glucose, AAs
-filtration and partial reabsorption: Na, Cl, bicarb
-filtration and secretion: K+, H+, organic acids/bases

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9
Q

How do the rates of filtration, reabsorption, and excretion compare to one another?

A

the rates of filtration and reabsorption are extremely large compared to the rate of excretion

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10
Q

What are the characteristics of the glomerular basement membrane?

A

-has proteoglycans with a strong neg. charge
-prevents certain proteins like albumin from filtering out
-epithelial layer is not continuous; has “slit pores”
-epithelial layer also has neg. charge to repel plasma proteins

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11
Q

Which characteristics of molecules determine their filterability?

A

-size
-electrical charge

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12
Q

Which molecules are most readily filtered?

A

-those with a small molecular size
-those with a positive charge

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13
Q

What is the clinical correlation of the glomerular filtration barrier?

A

proteinuria/albuminuria can occur with changes in glomerular filtration barrier permeability

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14
Q

What does glomerular filtration rate represent?

A

the flow of plasma from the glomerulus into Bowman’s space over a specified period; chief measure of kidney function

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15
Q

What is the importance of a high GFR?

A

allows the kidneys to control the volume and composition of body fluids precisely and rapidly

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16
Q

What determines the GFR?

A

-sum of the hydrostatic and colloid osmotic forces across the glomerular membrane (net filtration pressure)
-glomerular filtration coefficient Kf
-GFR = Kf x net filtration pressure

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17
Q

Why does Bowman’s capsule not have an oncotic pressure?

A

no protein should be passing the filter

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18
Q

Why do the glomerular capillaries have a high filtration rate?

A

-higher hydrostatic pressure
-high Kf

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19
Q

What is filtration fraction?

A

-the portion of plasma entering the kidney that ends up as filtrate
-GFR/RPF

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20
Q

What percent of the plasma flowing through the kidney is filtered through the glomerular capillaries?

A

20%

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21
Q

Which factors affect the GFR?

A

-glomerular hydrostatic pressure
-glomerular oncotic pressure
-renal plasma flow
-filtration coefficient Kf
-balance between afferent and efferent resistance

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22
Q

Why does the glomerular oncotic pressure gradually increase through the glomerulus?

A

filtration of water concentrates the proteins since they are not filtered, which elevates the oncotic pressure

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23
Q

What is the average colloid oncotic pressure of the glomerular capillary plasma proteins?

A

32 mmHg

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24
Q

Which two factors influence the glomerular capillary colloid osmotic pressure?

A

-arterial plamsa colloid osmotic pressure
-fraction of plasma filtered by glomerular capillaries

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25
How does increasing the arterial plasma colloid osmotic pressure impact GFR?
decreases GFR
26
How does increasing the filtration fraction impact GFR?
decreases GFR
27
What happens when there is a reduction in renal plasma flow with no initial change in GFR?
-increase in filtration fraction -raise glomerular capillary colloid osmotic pressure -leads to reduced GFR
28
What happens when there is an increase in renal blood flow?
-decrease in filtration fraction -slower rise in the glomerular capillary colloid osmotic pressure -less inhibitory effect on GFR/potential increase in GFR
29
What is the primary means of physiological regulation of GFR?
changes in glomerular hydrostatic pressure
30
How does a change in glomerular hydrostatic pressure impact GFR?
-increased pressure raises GFR -decreased pressure lowers GFR
31
Which variables impact glomerular hydrostatic pressure?
-arterial pressure -afferent arteriolar resistance -efferent arteriolar resistance
32
How does increased arterial pressure impact GFR?
raises glomerular hydrostatic pressure, which increases GFR
33
How does increased resistance of afferent arterioles impact GFR?
reduces glomerular hydrostatic pressure, which decreases GFR
34
How does constriction of efferent arterioles impact GFR?
increases resistance to outflow, which raises glomerular hydrostatic pressure and increases GFR slightly (as long as resistance does not reduce renal blood flow too much)
35
What happens if constriction of efferent arterioles is severe?
-rise in colloid osmotic pressure exceeds increase in glomerular capillary hydrostatic pressure -net force for filtration decreases, reducing GFR
36
Why is the renal blood flow to the kidneys about 22% of the cardiac output?
-to supply the kidneys with nutrients and remove waste products -to supply enough plasma for the high rates of glomerular filtration necessary for precise regulation of body fluid volumes and solute concentrations
37
What is the equation for renal blood flow?
(renal artery pressure - renal vein pressure)/total renal vascular resistance
38
What determines the total vascular resistance through the kidneys?
the sum of the resistances in the individual vasculature segments
39
Where does the majority of renal vascular resistance reside?
-interlobular arteries -afferent arterioles -efferent arterioles
40
What controls the resistance in renal vasculature?
-sympathetic nervous system -hormones -local internal control mechanisms
41
How do increases and decreases in vasculature resistance impact renal blood flow?
-increases in resistance decrease blood flow -decreases in resistance increase blood flow
42
What is the function of autoregulation?
allows the kidneys to maintain renal blood flow and GFR at a relative constant over a range of arterial pressures
43
Which region of the kidney receives the majority of the blood flow?
cortex
44
Which portion of the peritubular capillary system supplies blood to the medulla?
vasa recta
45
What happens when there is strong activation of the sympathetic nervous system?
-constriction of the renal arterioles -decrease in renal blood flow and GFR
46
What happens when there is mild/moderate activation of the sympathetic nervous system?
-little influence on blood flow and GFR -stimulates renin release and increased tubular reabsorption -decreased sodium and water excretion
47
What is an autacoid?
physiologically active substance produced by the body that typically has a localized effect of brief duration
48
What are the effects of epinephrine/norepinephrine on the kidneys?
-constrict afferent and efferent arterioles -reduce GFR and renal blood flow
49
What are the characteristics of endothelin?
-peptide released by damaged vascular endothelial cells of the kidneys -may contribute to hemostasis -powerful vasoconstrictor
50
What are the characteristics of endothelial-derived nitric oxide?
-autacoid that decreases renal vascular resistance -released by vascular endothelium -important for maintaining vasodilation
51
What effect do drugs that inhibit nitric oxide formation have?
-increase renal vascular resistance -decrease GFR and urinary sodium excretion -cause high blood pressure
52
What are the functions of prostaglandins and bradykinin?
-cause vasodilation -increase renal blood flow and GFR -may dampen the renal vasoconstrictor effects of sympathetic nerves and angiotensin II
53
What are the characteristics of angiotensin II?
-powerful renal vasoconstrictor -formed in kidneys and in systemic circulation -receptors present in virtually all blood vessels of the kidneys
54
Which vessels are protected from angiotensin II, and how?
-preglomerular blood vessels, especially afferent arterioles -protection is due to release of vasodilators (nitric oxides, prostaglandins) which counteract the vasoconstrictor effects of angiotensin II
55
Which vessels are highly sensitive to angiotensin II, and why?
-efferent arterioles -increased angiotensin II levels raise glomerular hydrostatic pressure; prevents decreases in glomerular hydrostatic pressure and GFR -decreased blood flow caused by constriction increases sodium and water reabsorption to restore blood volume and blood pressure
56
What is the importance of autoregulation?
prevent potentially large changes in GFR and renal excretion of water that would otherwise occur with changes in blood pressure
57
Why does arterial pressure exert a lesser effect on urine volume?
-renal autoregulation prevents large changes in GFR -additional adaptive mechanisms cause an increase in reabsorption when GFR rises
58
What are the two components of the tubuloglomerular feedback mechanism?
-afferent arteriolar feedback mechanism -efferent arteriolar feedback mechanism
59
What are the components of juxtaglomerular complex?
-macula densa cells in distal tubule -juxtaglomerular cells in walls of afferent and efferent arterioles
60
How does a decreased GFR impact the Loop of Henle?
-slows flow rate of LOH -increases reabsorption of sodium and chloride ions delivered to ascending LOH -reduces concentration of sodium chloride at macula densa cells
61
What effects do the macula densa cell signals have when NaCl conc. is decreased?
-decreases resistance to blood flow in the afferent tubules -increases renin release from juxtaglomerular cells; leads to angiotensin II causing efferent arteriole constriction
62
How does high protein intake impact renal blood flow and GFR?
increases blood flow and GFR
63
Why is it important that amino acids and sodium are reabsorbed together?
increased amino acid reabsorption stimulates increased sodium reabsorption when protein intake is high
64
How do large increases in blood glucose levels impact renal blood flow and GFR?
increases blood flow and GFR
65
What happens when proximal tubular reabsorption is reduced?
-ability to reabsorb sodium chloride is decreased, leading to large amounts of sodium chloride reaching the distal tubule -can quickly cause excessive volume depletion without compensatory mechanisms
66
Why is it important that an increase in reabsorption of NaCl prior to the macula densa increases renal blood flow and GFR?
helps return distal sodium chloride delivery to normal in order to maintain normal rates of sodium and water excretion
67
What is the importance of the myogenic reflex?
-prevents excessive stretch of the vessel -raises vascular resistance -helps prevent excessive increases in renal blood flow and GFR -protects kidney from hypertension-induced injury
68
What are the characteristics of creatinine?
-byproduct of muscle metabolism -freely filtered while not being reabsorbed or secreted -used to measure glomerular filtration -increased serum creatinine indicates decreased renal clearance

SP1 Physiology/Microanatomy 2 (50 decks)

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