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tACCP > Renal Physiology > Flashcards

Renal Physiology Flashcards

1
Q

What percentage of renal blood flow goes to the medulla?

A

10%

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2
Q

What is the glomerular filtration rate (GFR)?

A

125 ml/min

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3
Q

What is the hydrostatic pressure in Bowman’s capsule?

A

~10 mmHg

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4
Q

What effect does increased glomerular capillary pressure have on filtration?

A

It increases GFR.

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5
Q

What molecule is poorly filtered due to size and charge?

A

Albumin (69,000 Da, negatively charged).

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6
Q

What is the primary function of podocytes?

A

Create filtration slits that restrict large molecules.

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7
Q

What happens if the efferent arteriole resistance increases?

A

Glomerular pressure rises, enhancing filtration.

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8
Q

What factors determine the ultrafiltration coefficient (KF)?

A

Membrane permeability and surface area.

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9
Q

What is the function of autoregulation in the kidneys?

A

Maintain constant GFR and renal blood flow.

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10
Q

What role does the myogenic mechanism play in autoregulation?

A

Responds to stretch by inducing vasoconstriction.

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11
Q

What is the role of the juxtaglomerular apparatus (JGA)?

A

Senses changes in NaCl and flow for feedback regulation.

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12
Q

How does adenosine mediate tubuloglomerular feedback?

A

Constricts afferent arterioles to reduce GFR.

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13
Q

What is the effect of nitric oxide on renal blood flow?

A

Promotes vasodilation.

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14
Q

What happens to GFR during sympathetic stimulation?

A

It decreases due to vasoconstriction.

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15
Q

What is the effect of angiotensin II on renal blood vessels?

A

Preferentially constricts efferent arterioles.

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16
Q

What happens when afferent arterioles constrict?

A

GFR decreases.

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17
Q

Why is inulin the gold standard for GFR measurement?

A

Freely filtered, not reabsorbed, secreted, or metabolized.

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18
Q

What is a drawback of using creatinine to measure GFR?

A

Slightly secreted by tubules, leading to overestimation.

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19
Q

What does renal clearance represent?

A

Volume of plasma cleared of a substance per unit time.

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20
Q

What condition increases plasma creatinine concentration?

A

Reduced GFR.

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21
Q

How is renal blood flow (RBF) calculated?

A

RBF = RPF / (1 - Hematocrit).

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22
Q

What property makes PAH suitable for measuring RPF?

A

It is almost completely cleared from plasma.

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23
Q

What is the renal plasma flow (RPF) value?

A

~600 ml/min.

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24
Q

Why is PAH only accurate at low concentrations?

A

High concentrations saturate secretion mechanisms.

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25
Q

What percentage of filtrate is reabsorbed by the end of the proximal tubule?

A

~70%.

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26
Q

What is the primary transport mechanism for Na+ in the proximal tubule?

A

Na+/K+ ATPase pump.

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27
Q

What role do tight junctions play in the nephron?

A

Facilitate paracellular transport of solutes like Cl-.

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28
Q

What drives reabsorption of water in the proximal tubule?

A

Osmotic gradients created by Na+ and HCO3- reabsorption.

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29
Q

Which part of the nephron generates concentrated filtrate?

A

Loop of Henle.

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30
Q

What is the function of principal cells in the collecting duct?

A

Regulate Na+ reabsorption and K+ secretion.

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31
Q

What is the role of intercalated cells in the collecting duct?

A

Acid-base balance via H+ and HCO3- transport.

32
Q

What is the osmolarity of fluid entering the distal tubule?

A

Hypotonic (~100 mOsm/L).

33
Q

What is the osmolality at the tip of the loop of Henle?

A

Up to 1400 mOsm/kg.

34
Q

Which segment of the loop actively transports NaCl?

A

Thick ascending limb.

35
Q

How does the vasa recta maintain the medullary gradient?

A

Countercurrent exchange prevents gradient dissipation.

36
Q

Why is the thin descending limb permeable to water?

A

Presence of aquaporins.

37
Q

What generates the positive charge in the thick ascending limb?

A

K+ recycling into the lumen via channels.

38
Q

How does urea contribute to medullary osmolality?

A

Reabsorbed in collecting ducts, recycled in the loop.

39
Q

What is the effect of furosemide on the loop of Henle?

A

Inhibits Na+/K+/2Cl- cotransporter, reducing NaCl reabsorption.

40
Q

Why does the medulla have low oxygen tension?

A

Countercurrent exchange lowers PO2 at the vasa recta tip.

41
Q

What triggers ADH release?

A

Increased osmolality or decreased blood volume.

42
Q

What is the role of aldosterone in potassium regulation?

A

Enhances K+ secretion in the distal tubule.

43
Q

What hormone inhibits Na+ reabsorption in the distal nephron?

A

Atrial natriuretic peptide (ANP).

44
Q

What makes the distal tubule impermeable to water without ADH?

A

Lack of aquaporins in the absence of ADH.

45
Q

What drives calcium reabsorption in the distal tubule?

A

PTH and vitamin D activation.

46
Q

What happens to osmolality in the collecting duct in the presence of ADH?

A

Increases as water is reabsorbed.

47
Q

Which type of nephron is most involved in concentrating urine?

A

Juxtamedullary nephrons.

48
Q

What percentage of filtered Na+ is reabsorbed in the distal nephron?

A

~10%.

49
Q

What stimulates ANP release?

A

Atrial stretch due to increased blood volume.

50
Q

What enzyme catalyzes angiotensin I formation?

A

Renin.

51
Q

How does aldosterone increase Na+ reabsorption?

A

Upregulates Na+/K+ ATPase pumps and Na+ channels.

52
Q

What effect does ANP have on GFR?

A

Increases it by dilating afferent arterioles.

53
Q

What suppresses renin release?

A

Increased angiotensin II and Na+ levels.

54
Q

How does sympathetic activation affect renin?

A

Increased angiotensin II and Na+ levels.

55
Q

How does sympathetic activation affect renin?

A

Stimulates release via β1 receptors.

56
Q

What role does ADH play in urea recycling?

A

Facilitates its movement into the medulla to maintain osmotic gradient.

57
Q

What suppresses ADH release?

A

Alcohol consumption.

58
Q

How is filtered bicarbonate reabsorbed in the nephron?

A

Combines with H+ to form CO2 and H2O.

59
Q

What enzyme is critical for bicarbonate reabsorption?

A

Carbonic anhydrase.

60
Q

Where is ammonium generated in the nephron?

A

Proximal tubule via glutamine metabolism.

61
Q

What is the role of the Na+/H+ antiporter?

A

Secretes H+ into the tubular lumen.

62
Q

What happens to NH4+ in the thick ascending limb?

A

Reabsorbed and dissociates into NH3 and H+.

63
Q

What buffers H+ in the collecting duct?

A

Ammonia (NH3) and phosphate.

64
Q

What is the renal compensation for respiratory acidosis?

A

Increased H+ excretion and bicarbonate reabsorption.

65
Q

How does aldosterone affect acid-base balance?

A

Promotes H+ secretion in the distal nephron.

66
Q

What type of muscle controls the internal urethral sphincter?

A

Smooth muscle.

67
Q

What initiates the micturition reflex?

A

Stretch receptors in the bladder wall.

68
Q

What is the detrusor muscle?

A

Smooth muscle responsible for bladder contraction.

69
Q

What is the role of higher brain centers in micturition?

A

Voluntary control of the external sphincter.

70
Q

Where is erythropoietin (EPO) produced?

A

In renal cortex fibroblast-like cells.

71
Q

What triggers EPO production?

A

Hypoxia via HIF1-alpha stabilization.

72
Q

What is the role of the kidneys in vitamin D metabolism?

A

Activate 25(OH)D to 1,25(OH)2D.

73
Q

Which ion is most closely regulated by the kidneys to control blood volume?

A

Sodium.

74
Q

What is the renal threshold for glucose?

A

~11 mmol/L.

75
Q

Why is potassium regulation critical?

A

Prevents hyperkalemia, which can cause cardiac arrhythmias.

76
Q

What happens to urine osmolality in the absence of ADH?

A

Becomes dilute (~50 mOsm/L).

tACCP (4 decks)

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