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NUT1005 > Renal Physiology > Flashcards

Renal Physiology Flashcards

1
Q

What are the three main kidney functions

A

Regulation of water electrolyte balance
Removal of waste
Secretion of hormones

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2
Q

What 3 hormones are secreted from the kidney

A

Erythropoietin (RBC synthesis)
Renin
1,25 dihydroxyvitamin D (bioactive form)

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3
Q

What is the function of the lower urinary tract (ureters, bladder and urethra)

A

Urine collection, storage and excretion

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4
Q

What are the blood vessels connected to kidney

A

Renal artery and renal vein

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5
Q

What makes up the cortex of the kidney

A

Glomeruli

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6
Q

What makes up the medulla of the kidney

A

Renal tubules, collecting ducts, blood vessels and medullary pyramids

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7
Q

What are the important features of the renal system

A

Kidneys have excellent blood supply (20% of cardiac output) enabling them to work with the cardiovascular system in an intergrated manner by processing plasma of blood (control blood volume)

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8
Q

What is a nephron

A

Functional unit of kidney

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9
Q

What are the 2 functional components of the nephrons

A

Vascular component (contains blood) and tubular component (contains urine)

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10
Q

What does the mechanisms of the kidneys depend on

A

The relationship between the vascular and tubular components

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11
Q

What is the the pattern of blood flow from the aorta to the kidney and back to the heart

A

Aorta- renal artery- afferent arterials- glomerulus- efferent arteriole- peritubular capillaries- renal vein - inferior vena cava

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12
Q

What are the two main components of the nephron

A

Golmerulus and tubule

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13
Q

What is the function of the glomerulus

A

Forms a protein free filtrate from blood

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14
Q

What is the function of the tubule

A

Processes the filtrate to form urine

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15
Q

What are the 4 segments of each tubule

A

Proximal tubule, loop of Hemel, distal tubule and collecting ducts

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16
Q

Where does filtration occur

A

The glomerulus

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17
Q

Where does water and solute reabsorption occur

A

PCR, loop of henle, DCT and collecting ducts

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18
Q

Where does secretion occur

A

PCT, DCT and collecting ducts

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19
Q

Where does the golmerular filtrate drain into

A

The bowman’s capsule

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20
Q

What is the function of the pores in the capillary endothelium of the glomerulus

A

Enables small molecules to pass into the bowman’s capsule but not larger proteins and RBC

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21
Q

What stops plasma proteins from entering the tubular fluid

A

The negative charge of podocytes and the basement membrane of the glomerulus

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22
Q

Why does ca2+ not pass through into the capsule

A

50% is bound plasma proteins

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23
Q

What is the glomerular filtrate rate

A

180l/day

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24
Q

What is the function of glomerular filtration

A

Regulate the composition of extracellular fluid

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25
Q

What two things control glomerular filtrate rate (GFR)

A

The diameters of afferent and efferent arterioles

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26
Q

Why causes high hydrostatic pressure at glomerular capillaries

A

Short, wide afferent arteriole and and long, narrow efferent arteriole

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27
Q

What regulates the diameter of the efferent and afferent arterioles/ GRF

A

Sympathetic vasoconstrictor nerves, ADH and RAAS

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28
Q

What is the function of the peritubular capillaries

A

Provide nutrients for tubules and receive the fluid that the tubules have reabsorbed

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29
Q

Why does reabsorption not filtration occur in the peritubular capillaries

A

As oncotic pressure is greater than hydrostatic pressure

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30
Q

Why must reabsorption of fluid in the peritubular capillaries occur

A

As we filter 180L/day but only excrete 1-2l/day of urine

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31
Q

Where does most reabsorption of nutrients, ions, water and urea occur

A

The proximal convoluted tubule

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32
Q

How are glucose, AA, phosphate ions and chloride ions reabsorbed in the proximal tubules

A

Coupled with Na+ and transported down electrochemical gradient for Na+, requiring energy
Gradient established by Na+/K+- ATPase
Move across basolateral membrane by passive or facilitated diffusion into peritubular capillaries

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33
Q

How are peptides reabsorbed in proximal tubules

A

Taken up by pinocytosis and degraded by cells to AA so they can cross the basolateral membrane

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34
Q

What is the Tm

A

Maximum transport capacity of transporter proteins in tubules

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35
Q

What happens if the maximum transport capacity is exceeded

A

Excess nutrient is excreted in urine, which is useful for disease detection

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36
Q

Why do amino acids have a high maximum transport capacity

A

Because we need to preserve as many as possible

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37
Q

How is Na+ absorbed in the tubules

A

By active transport mechanism instead of a Tm mechanism, basolateral ATPases establish the gradient for Na+ to cross the tubule wall
Na+ ions move down this concentration gradient via Na channel proteins
Cl- follow Na+ to maintain an electrochemical gradient

38
Q

How does the reabsorption of Na+ affect the fluid in the tubules

A

Becomes more concentrated as H2O follows Na+ due to osmotic gradient

39
Q

How is glucose reabsorbed in the tubules

A

Apical- Na+/ glucose cotransporter (SGLT) down Na+ conc gradient, requiring Na+/k+-ATPASE
Basolateral- glucose transporters (GLUTS) down concentration gradient

40
Q

How are amino acids reabsorbed in the tubule

A

Apical- Na+/ amino acids cotransporter (SGLT) down Na+ conc gradient, requiring Na+/k+-ATPASE
Basolateral- passive diffusion down concentration gradient

41
Q

How is K+ reabsorbed in the proximal convoluted tubule

A

Reabsorbed in promximal convoluted tubule
Passive via K+ selective ion channel following movement of Na+ and fluid

42
Q

Where is K+ secreted

A

Cortical collecting ducts

43
Q

How is K+ secreted into the cortical collecting ducts

A

Via active transport of K+ across basolateral membrane and passive exit across apical membrane into the tubular fluid

44
Q

What controls K+ excretion

A

RAAS mediated Na+ absorption

45
Q

Why is K+ regulation important

A

Too high (from 4 to 5.5 moles/l) = hyperkalaemia (ventricular fibrillation and death)
Too low (from 4 to 3.5 mmoles/l)= hypokalaemia (hyperpolarise= arrhythmias and paralysis and death)

46
Q

What maximises K+ excretion when it is too high

A

Medullary trapping of K+ in the PCT

47
Q

Describe the osmoraility is the glomerular filtrate after the PCT

A

Isotonic with the plasma

48
Q

What is the main function of the loop of Henley and collecting ducts

A

Absorption of water and sodium chloride

49
Q

What does absorption of water and sodium chloride in the loop of henle and collecting ducts facilitate

A

Fine tuning of urine according to the body’s needs

50
Q

What is the counter current exchange

A

The relationship between permeability of the descending thin limb and ascending thin limb to Na+

51
Q

How is Na+ removed from the ascending thin limb

A

Actively transported into interstitial fluid surround limb

52
Q

What regulates the cyclical movement of Na+ throughout the loop of helpless

A

ADH (increases water permeability)

53
Q

What occurs in the descending limb of the loop of henle and how does this affect filtrate osmorality

A

Water reabsorbed, increasing the osmorailty

54
Q

What occurs in the ascending limb of the loop of henle and how does this affect filtrate osmorality

A

Active solute reabsorption, decreased filtrate osmorailty

55
Q

What is the vasa recta

A

Blood vessel that removes water leaving the loop of henle

56
Q

What occurs in the descending limb of the vasa recta and how does this affect filtrate osmorality

A

Water reabsorption and solute uptake, increased blood osmorailty

57
Q

What occurs in the ascending limb of the vasa recta and how does this affect filtrate osmorality

A

Water reabsorption
Descreased blood osmorailty

58
Q

What is the descending limb of the loop more permeable to

A

H20

59
Q

What is the descending limb of the loop less permeable to

A

Na+ and Cl-

60
Q

What is the descending limb of the loop impermeable to

A

Urea

61
Q

What does not happen in the descending limb of the loop

A

Active transport of solutes

62
Q

What happens to the osmorailty of the extracellular fluid surrounding the descending limb of the loop from the PCT

A

Progressively increases

63
Q

What does high osmorailty mean

A

More concentrated

64
Q

What is the ascending limb of the loop less permeable to

A

H20

65
Q

What is the ascending limb of the loop moderately permeable to

A

Urea

66
Q

What is the ascending limb of the loop more permeable to

A

Na+ and Cl-

67
Q

What happens in the ascending limb of the loop of henle

A

Na+ diffuses from tubules to extracellular fluid surrounding both limbs
Urea enters tubules down concentration gradient
Thick ascending limb reabsorbs Na+ from extracellular fluid via apical Na+-K+-ATPase. Cl- diffuses across basolateral membrane

68
Q

Describe the countercurrent multiplier exchange in the loop of henle

A

Filtrate entering the descending becomes progressively more concentrated as it loses water (increased osmolarity of filtrate)
Blood in the vasa recta removes water leaving the loop of henle and the descending limb of the vasa recta uptakes Na+, Cl- and K+ (increased osmorality so the ascending limb can reabsorb more water (decreased osmorality)
The ascending limb pumps out Nat, K+, and Cl- and filtrate becomes hyposmotic (decreased osmolality of filtrate)

69
Q

What is the function of the collecting ductsm

A

Runs through hyper osmotic (high osmorality) medulla to drain into renal pelvis and uterers
Water moves down osmotic gradient to extracellular fluid to produce concentrated urine

70
Q

What controls Na+ reabsorption at the collecting ducts

A

Tight epithelium junctions and aldosterone (from RAAS)

71
Q

How is membrane permeability to water increased in the collecting ducts

A

ADH activates adenylate cyclase and cAMP to increase the permeability of the apical membrane to water

72
Q

What are the macula densa

A

Specialised region of cells in DCT (in close proximity to bowman’s capsule) that sense Na+ in glomerular filtrate

73
Q

What happens if the macula densa sense low Na+ in glomerular filtrate

A

Cells on afferent arteriole within the juxtaglomerular apparatus (JGA), includes JG cells that secrete renin, help regulate renal blood flow, GFR and also indirectly, modulates Na+ balance and systemic BP

74
Q

Describe the role of ADH in the collecting duct

A

Changes in plasma osmolality (in carotid artery) detected by osmoreceptors in hypothalamus.
Stimulates release of anti-diuretic hormone from posterior pituitary (reduce osmolality decreases ADH)
ADH receptors present on basolateral membrane, ADH binds, G protein activated, adenylate cyclase activated, ATP converted to cAMP, protein kinase A (PKA) activated, PKA phosphorylates target proteins causing endosomes containing aquaporins to fuse with membrane, increase incorporation of aquaporin channels into apical membrane
Due to high Na+ in extracellular fluid in medulla water moves from CD tubule into the medulla (concentrating urine)

75
Q

What do juxtaglomerular apparatus cells (within afferent arteriole) secrete

A

Renin

76
Q

How is urea reabsorbed

A

Passively

77
Q

When is urea reabsorption greatest

A

When urine volume per minute is small (concentrated urine)

78
Q

What is urea recycling

A

Urea is toxic at high levels but useful in small amounts, recycling causes a build up in inner medulla which helps create the osmotic gradient for water reabsorption at the loop of henle

79
Q

What can cause more urea/more concentrated urine

A

High protein diet

80
Q

What is the function of urea

A

Concentrating urine

81
Q

What is the role of angiotensin in DCT and glomerulus

A

Increase Na+ and water retention, increase extracellular fluid and increase blood pressure via vasoconstriction in arterioles

82
Q

What causes efferent arteriole vasoconstriction

A

Low dose of Angiotensin II

83
Q

What causes afferent arteriole vasoconstriction

A

High dose of angiotensin II

84
Q

What is the function of renin

A

Stimulates release of angiotensin from liver into blood to stimulate vasoconstriction

85
Q

What is the function of aldosterone

A

Aldosterone stimulates Na+ uptake on the apical cell membrane in the distal convoluted tubule and collecting ducts

86
Q

What causes the secretion of aldosterone from adrenal cortex

A

Angiotensin II

87
Q

How is chronic kidney disease identified

A

Chronic kidney disease is identified by a blood test for creatinine. Higher levels of creatinine indicate a lower GFR and as a result a decreased capability of the kidneys to excrete waste products

88
Q

What is normal blood pH

A

7.35-45

89
Q

How does the kidney regulate blood pH

A

via the active transport of H+ ions into the filtrate

90
Q

What is associated with high GRF

A

aff art dilation and eff art constriction

91
Q

What is the pH of urine

A

4-8

92
Q

How is plasma pH buffered in the kidney

A

CO2 actively transported out of peritubular capillaries
CO2 combines with water to form HCO3- and H+
Secretion of H+ either slows or increases until the pH returns to normal
Excess H+ buffered by HCO3-

NUT1005 (18 decks)

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