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Renal > Physiology 1, 2 & 3 > Flashcards

Physiology 1, 2 & 3 Flashcards

1
Q

What is osmolarity?

A

Number of osmotically active particles ia substance overall

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2
Q

What is osmolality?

A

Number of osmoles per kg of water

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3
Q

What is the main component of ECF and therefore the major determinant of ECF volume?

A

NaCl

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4
Q

What is tonicity?

A

Tonicity of a solution refers to its effect on the volume of a cell - hypertonic, hypotonic or isotonic.

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5
Q

A solution that is isotonic has what concentration of NaCl?

A

150osmol/l

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6
Q

What makes up ECF?

A

Plasma (~20%)
Interstitial fluid (~80%)
Lymph (neglible) and transcellular fluid (neglible)

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7
Q

What is a tracer?

A

Compound that is added to the body (oral/injection) that distributes in the body fluid compartments indicating the size of the compartment.

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8
Q

Name 3 tracers and what they are used to measure?

A

3H2O - Total body water
Inulin - ECF
Labelled albumin - Plasma

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9
Q

Total body water is equal to what?

A

ICF + ECF

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10
Q

What is the equation to measure the distribution volume?

A

Quantity of tracer (mol)/ equilibration volume of tracer in body (mol/l)

Qx mol/ [X] mol/l

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11
Q

How does water imbalance manifest?

A

Changes in body fluid osmolarity

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12
Q

What is the main cation and anion of ECF?

A

Cation - Na+

Anion - Cl-

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13
Q

Are the osmotic concentrations of ECF and ICF identical?

A

Yes

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14
Q

What is fluid shift?

A

Movement of water between the ICF and ECF in response to an osmotic gradient

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15
Q

What does the kidney do to ECF?

A

Alters composition and volume of ECF

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16
Q

Regulation of what is vital for long term regulation of blood pressure?

A

ECF volume

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17
Q

What are the 3 challenges to fluid homeostasis and what do they result in?

A

Gain or loss of water - change in fluid osmolarity - similar changes in ICF and ECF volumes

Gain or loss of NaCl - change in fluid osmolarity - If ECF gains Na then ICF losses Na and vice versa

Gain or loss of isotonic fluid - no change in fluid osmolarity - change in ECF volume only

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18
Q

Can the total electrolyte concentration affect water balance?

A

Yes

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19
Q

Can the total concentration of individual electrolytes affect cell function?

A

Yes - esp. Na+ and K+

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20
Q

Potassium has a key role in what?

A

Establishing membrane potential - must be closely monitored and regulated

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21
Q

Salt imbalance is manifest as what?

A

Changes in ECF volume

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22
Q

List the 10 functions of the kideny.

A 
Water balance 
Salt balance 
Acid base balance 
Maintenance of plasma volume  
Maintenance of plasa osmolarity 
Excretion of metabolic waste products (urea)
Excretion of exogenous foreign compounds (drugs)
Secretion of renin 
Secretion of erythropoietin 
Conversion of Vit D into active form
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23
Q

Total ingested + total produced has to be = to what for homeostasis?

A

Total excreted + Total consumed

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24
Q

What is the functional unit of the kindey and what are it’s functions?

A

Nephron
Filtration
Tubular reabsorption
Tubular secretion

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25
Q

What are the 2 types of nephrons?

A

Juxtamedullary and cortical

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26
Q

Why is the renal tubule a key site of regulation?

A

Because the flow through the JGA is controlled

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27
Q

What is the glomerulus highly permeable to and what is it not permeable to?

A

Highly permeable to blood but not proteins or cells

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28
Q

The highly modified endothelium surrounding the glomerulus is associated with what?

A

Podocytes

29
Q

What are podocytes?

A

Controlled site for fluid filtration that provide a high surface area for easily permeable fluid formation

30
Q

The juxtaglomerular apparatus includes..?

A

Bowmans capsule
glomerulus
Part of the distal tubule

31
Q

What is urine?

A

Modified filtrate of blood

32
Q

What percentage of plasma that enters the glomerulus is actually filtered?

A

20%

33
Q

Describe tubular resorption.

A

Primary filtrate is absorbed back into the efferent arteriole

34
Q

Describe tubular secretion.

A

Particles/cells from efferent arteriole are secreted into the kidney tubule for excretion

35
Q

Reabsorption (TR) + Excretion should = what for homeostasis?

A

Filtration (GF) and Secretion (TS)

36
Q

How do you calculate the rate of filtration of a substance?

A

Rate of filtration of X = [X]plasma x GFR

37
Q

How do you calculate the rate of excretion of a substance?

A

Rate of excretion of X = [X]urine x Vu

38
Q

What is the GFR?

A

Rate at which protein-free plasma is filtered from the glomeruli into the Bowman’s capsule per unit time (mins)

39
Q

What is the equation for calculating the rate of reabsorption of a substance?

A

Rate of reabsorption of X =
Rate of filtration of X - rate of excretion of X =
([X]plasma x GFR ) - ([X]urine x Vu )

40
Q

What is Vu?

A

Urine flow rate

41
Q

How do you calculate the rate of secretion of a substance?

A

Rate of excretion of X - rate of filtration of X =

[X]urine x Vu) - ([X]plasma x GFR

42
Q

How much filtered chlorine is reabsorbed in the kidneys?

A

Almost all of it

Same for key ion (Na & K) and glucose and amino acids

43
Q

What are the barriers to filtration and which particles are they barriers to?

A 
Glomerular capillary endothelium (barrier to RBCs)
Basement membrane (barrier to plasma proteins)
Slit processes of podocytes (barrier to plasma proteins)
44
Q

What are the forces that favour filtration? What are their pressures?

A

Bowman’s capsule oncotic pressure - 0mmHg

Glomerular capillary blood pressure - 55mmHg

45
Q

What are the forces that oppose filtration? What are their pressures?

A

Bowman’s capsule hydrostatic pressure - 15mmHg

Capillary oncotic pressure - 30mmHg

46
Q

What is the NET filtration pressure?

A

10mmHg

47
Q

How is GFR calculated? What is normal GFR?

A

Kf x net filtration pressure = normal 125ml/min

48
Q

What does Kf stand for?

A

Filtration coefficient

49
Q

What is the major determinant of GFR?

A

Glomerular capillary blood pressure (BPgc)

50
Q

What is the extrinsic mechanism of regulation of GFR?

A

Sympathetic control via baroreceptor reflex

51
Q

How would the extrinsic control mechanism of GFR regulation deal with a decreased blood pressure?

A 
Increased sympathetic activity 
Constriction of afferent arterioles 
Decreased Glomerular capillary blood pressure (BPgc)
Decreased GFR 
Decreased urine
52
Q

What are the 2 parts of the intrinsic autoregulation of GFR?

A

Myogenic mechanism

Tubuloglomerular feedback mechanism

53
Q

What is the myogenic mechanism?

A

If vascular smooth muscle is stretched (increased arterial pressure) the arterioles contract thus constricting the lumen

54
Q

Which cells in the JGA release renin?

A

Granular cells

55
Q

The macula densa cells in the JGA do what?

A

Sense NaCl content of tubular fluid

56
Q

Define plasma clearance.

A

Volume of plasma copletely cleared of a particular substance per minute

57
Q

What is the calculation for plasma clearance?

A

[X]urine x Vu / [X]plasma = … ml/min

58
Q

What 2 substaces could have their clearance values calculated and this would = GFR.

A

Inulin
Creatinine - used clinically
Cinulin = GFR = ~125ml/min
Ccreatine = GFR = ~125ml/min

59
Q

What is the clearance value of a substance that is filtered, completely reabsorbed and not secreted?

A

0

glucose

60
Q

What is the clearance value of a substance that is not filtered and not secreted?

A

0

61
Q

What is the clearance value of a substance that is filtered, partly reabsrbed and not secreted?

A

Clearance < GFR
Substance is reabsorbed
Urea

62
Q

What is the clearance value of a substance that is filtered, secreted but not reabsorbed?

A

Clearance > GFR
substance is secreted into urine
H+

63
Q

If clearance = GFR what does this indicate?

A

Substance is neither reabsorbed nor secreted, simply filtered and passed to urine

64
Q

What substance is used clinically to measure renal plasma flow rate? What is this equal to?

A

PAH - filtered and fully secreted - all passed into urine
Renal plasma flow rate = 650ml/min
Cpah = 650ml/min

65
Q

If a substance is to be used as a clearance marker, what should it be?

A

Non-toxic
Inert (not-metabolised)
Easy to measure

66
Q

For a GFR marker, what should a substace be?

A

Filtered freely and not secreted or reabosorbed

67
Q

For a marker or renal plasma flow, a substance should be…

A

Filtered and completely secreted

68
Q

What is the filtration fraction?

A

The fraction of plasma flowing through the glomeruli that is filtered into the tubules
~20%

69
Q

What is the value of renal blood flow?

A

~1200ml/min

Renal (9 decks)

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