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physiology Flashcards

1
Q

what is the horizontal gradient between levels of the loop of Henle

A

200 mOsmol

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2
Q

how do stretch receptors in the bladder control micturition (babies/ spinal injuries)

A

become distended as the bladder fills (300- 350mls) until their output is large enough to stimulate parasympathetic system and relax external sphincter by inhibiting somatic neurones

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3
Q

what effect does hyperkalaemia/ hypokalaemia have on the body cells

A

hyperkalaemia - >5.5 - lower r.m.p –> ventricular fibrilation
hypokalaemia - <3.5 - increase r.m.p –> hyper polarise cells –> cardiac arrythmias

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4
Q

when the renal artery constricts what hormone is released

A

Renin

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5
Q

what is the HCO3 in blood

A

24 mmoles/ L (22- 26)

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6
Q

what is the pH of blood and how many H ions are free

A

7.4 (7.37 - 7.43)

4 x 10-6 mmoles/L free H - contribute to pH

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7
Q

what is the henderson hassebalch equation for pH

A

pH = HCO3/ PCO2

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8
Q

if a substance has a lower clearance that inulin what will happen

A

filtered and reabsorbed

[Ux] lower, [Px] higher

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9
Q

how do changes in osmolarity affect osmoreceptors

A

increases osmolarity - water out the cells, cells shrink, increased neural discharge
decreased osmolarity - water in the cells, cells swell, decreased neural discharge

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10
Q

what is the anion gap

A

difference between the sum of principal cations (Na and K) and principle anions (Cl and HCO3) in the plasma
normally 14-18 mmoles/L

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11
Q

what is the filtration fraction of the kidneys

A

19%

GFR/ Renal plamsa flow (55% of BV) x 100 = 125/660 x 100

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12
Q

when the mean arterial blood pressure increases, what happens to the afferent arteriole?

A

constricts - prevent rise in glomerular pressure

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13
Q

describe the process of ammonium excretion

A

in renal tubule cells - deamination of glutamine by renal glutaminase enzyme produces NH3
NH3 moves out tubule to combine with secreted H (fro CO2 in blood)
NH4 is formed in lumen which combines with Cl and NH4Cl is excreted in distal tubule

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14
Q

how does a metabolic alkalosis occur

A

HCO3 increase

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15
Q

what is the minimum and maximum pH of urine

A

min - 4.5-5

max - 8

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16
Q

what is used to estimate GFR

A

creatinine clearance

eGFR = 1/ [PCr]

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17
Q

in antidiuresis, how is urea retained to save water

A

reabsorbed from collecting duct into interstitium where it reinforces the interstitial gradient in the loops of Henle

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18
Q

if molecules X has filtration < excretion what will be the renal handling of X

A

net secretion

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19
Q

how do osmoreceptors regulate ADH secretion

A

increased osmolarity increased neural discharge mediated by osmoreceptors in the anterior hypothalamus

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20
Q

what is the mechanism for reabsorption of HCO3

A

active H secretion from tubule cells coupled to passive Na reabsorption
filtered HCO3 reacts with H to form H2CO3
with carbonic anhydrase this is converted into CO2 and H20
CO2 freely permeable and enters the cell
within the cell CO2 forms H2CO3 which dissociates to H and HCO3
the HCO3 ions pass into the peritbular capillaries with Na
(1 for 1 - no net gain)

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21
Q

how does increased sympathetic nerve activity impact renin release

A

increase release (B1 effect)

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22
Q

why can a big blood transfusion cause a metabolic alkalosis

A

bank blood contains citrate to prevent coagulation which is converted to HCO3

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23
Q

in the absence of ADH, what happens to water in the collecting duct

A

impermeable to H20 so large volumes of dilute urine are lost (compensate for H20 excess)

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24
Q

where does the majority of respiratory acid get buffered

A

97% within cells

rest within plasma proteins

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25
Q

what is the function of ANP

A

promotes Na excretion

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26
Q

what is the kidney regulation of HCO3 dependent on

A

active H ion secretion from the tubule cells into the lumen

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27
Q

how does the body respond to a low ECF to reduce blood pressure

A

reduced; ECF –> plasma volume –> venous pressure –> venous return –> atria pressure –> end diastolic volume –> systolic volumes –> cardiac output –> BP –> carotid sinus baroreceptor that normally inputs sympathetic discharge
increased sympathetic discharge

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28
Q

why is the oncotic pressure in peritubular capillaries so high

A

very concentrated plasma proteins

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29
Q

why is knowing GFR important in drug prescribing

A

if drug is excreted by the kidneys reduced GFR will increase drug concentration which may lead to toxicity
(adjust dose to appropriate renal function)

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30
Q

what factors affect serum creatinine

A

muscle mass
dietary intake
drugs

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31
Q

when is ANP released from he atria of the heart

A

response to expansion of ECF volume - causes natriuresis, loss of Na and H20 in urine

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32
Q

how do pudendal nerves control micturation

A

somatic motor neurones - innervate skeletal muscle of external sphincter, keeping it closed against strong bladder contractions (s2,3,4)
for micturition they must be inhibited by interneurones

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33
Q

how long do respiratory compensations take to occur

A

minutes

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34
Q

how does the kidney regulate HCO3

A

reabsorbing filtered HCO3

regenerating new HCO3

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35
Q

what blood pressure range is auto regulation effective in

A

60- 130 mmHg

filtration ceases <50 mmHg

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36
Q

how do juxtaglomerular cells act as renal baroreceptors

A

increase renin release when increased pressure in afferent arteriole

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37
Q

what can cause a metabolic alkalosis

A
  • H ions lost in vomiting
  • renal H lost in excess aldosterone/ liquorice (glycyrrhizic acid)
  • excess HCO3 administration in renal impairment
  • big blood transfusions
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38
Q

what is the equation for the buffer of plasma proteins

A

Pr + H –> HPr

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39
Q

what is the osomotic concentration of the fluid that leaves the proximal tubule

A

300 mOsmoles/ L - same as the plasma

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40
Q

what is used to measure renal plasma flow (RPF) and why

A

para-amino hippuric acid (PAH)

- freely filtered and actively secreted so plasma content is cleared of it

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41
Q

what is the net filtration pressure of the glomerulus

A

10 mmHg OUT

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42
Q

what is the vertical gradient of the loop of henle

A

300 -1200 mOsmol

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43
Q

what drug abolishes the the active transport of NaCl in the loop of henle

A

diuretics - furesmide
NaCLa nd H20 are no longer absorbed and concentration differences are lost - kidney produces a large amount of isotonic urine

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44
Q

what is oncotic pressure

A

osmotic force exerted on fluids by presence of proteins in the blood and tissue

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45
Q

where are the low and high pressure receptors

A

low - L and R atria and great veins

high - carotid and aortic baroreceptors

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46
Q

how does the body respond to a chronic metabolic acidosis

A

Renal correction increase H excretion and generate new HCO3 by ammonium excretion - need renal glutiminase (4-5 days)

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47
Q

how long does the kidney take to adapt to acid loads

A

4-5 days (chronic)

requires protein synthesis of renal glutiminase

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48
Q

how would the posterior pituitary respond to dehydration

A

increase ADH

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49
Q

what molecules share the same carrier molecule as Na

A

glucose, AA, HCO3

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50
Q

where is Angiotensin Converting Enzyme (ACE) found

A

throughout vascular endothelium

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51
Q

Where are the Na pumps in the proximal tubule

A

basolateral membrane

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52
Q

is the urea clearance higher or lower than inulin

A

lower - reabsorbed

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53
Q

which bladder sphincter is under voluntary control

A

external

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54
Q

how would low P receptors in atria respond to a reduction in ECF

A

decreased receptor discharge increases ADH released

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55
Q

In hypovolaemia, what affect does a reduction of atrial pressure have

A

Increases ADH secretion (low P receptors)

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56
Q

what is the normal decline of GFR

A

1ml/ min/ year after 30

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57
Q

how do pelvic nerves control micturation

A

parasymapthetic supply - increase contraction of detrusor muscle to increase pressure/ micturition (S2,3,4)

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58
Q

what would the ingestion of a hypertonic solution e.g seawater do to urine flow

A

Increase urine flow leading to dehydration

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59
Q

what 3 components on the glomerulus prevent solutes passing

A

fenestrations - RBC
basal lamina - larger proteins
still membrane between pedicles - medium sized proteins

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60
Q

what happens in the ascending limb of the loop of henle

A

fluid flows up
Na and Cl actively transported out of lumen into interstitium
impermeable to water

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61
Q

how does the body responf to metabolic acidosis

A

Increase PCO2 by decreasing ventilation

HCO3 lost in urine

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62
Q

If the pressure of the glomerular capillaries increases, what happens to filtration?

A

also increases

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63
Q

what are the main symptoms of diabetes insidious

A

polydipsia and polyuria (very large volumes of very dilute uric - >10 L day)

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64
Q

what is the maximum concentration of urine produced by the kidneys

A

1200- 1400 mOsmoles/L

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65
Q

what is the renal threshold for glucose

A

10 mmoles/l

way above plasma level of 5 mmoles/L - all is reabsorbed

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66
Q

how does a hyperglycaemic coma occur

A
  • glucose remains in tubule retaining water with it
  • decreased Na concentration in lumen as it is more diluted
  • reduced glucose and Na reabsorption (symport)
  • reduced movement of water in DESCENDING loop of henle (retain water)
  • fluid delivered to ascending limb is less concentrated
  • lower medullary interstitial gradient
  • macula densa detects high NaCl delivery so inhibits renin
  • ADH has no function can’t conserve H20
  • large volume of isotonic urine lost
  • inadequate brain flow of blood
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67
Q

in a drastic ECF volume change that affects MBP which receptors contribute to ADH secretion

A

carotid and aortic

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68
Q

how does ADH control the permeability of the collecting duct to water

A

aquaporins on the luminal membrane

cAMP secondary messenger system tell cells to insert pores into membrane

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69
Q

what happens to urea in the collecting duct in the presence of ADH

A

becomes more concentrated due to the removal of water

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70
Q

what does the activity of renal glutaminase depend on

A

pH - if pH falls, activity increases - more NH4 formed and excreted

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71
Q

what is a major source of alkali

A

oxidation of organic anions such as citrate

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72
Q

which receptors do moderate decreases in ECF affect

A

low P receptors in atria

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73
Q

what blood vessels are responsible for reabsorption

A

peritubular capillaries

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74
Q

what percentage of the filtrate is removed by the loop of henle

A

15-20% - up to 36L

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75
Q

what is the equation of the plasma clearance of X

A

Cx = [Ux} x V / [Px] in mls/ min

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76
Q

what causes urine to flow from kidneys to ureters

A

peristaltic contraction

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77
Q

what is the function of ACE

A

converts angiotensin I into angiotensin II

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78
Q

what is renal threshold

A

plasma threshold at which saturation occurs

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79
Q

what are the differences between central and peripheral diabetes insidious (ADH deficiency)

A

central - hypothalamic area is diseased from tumour, meningitis etc, treat with ADH
peripheral - collecting duct insensitive to ADH

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80
Q

how can acidosis lead to ventricular fibrillation and death

A

K is moved out of cells with H, leading to hyperkalaemia

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81
Q

if you increase the blood pressure of the glomerular capillaries, what happens to filtration

A

increases

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82
Q

what is the respiratory source of H

A

CO2 + H20 –> H2CO3 –> H + HCO3

ie formation of carbonic acid - in a healthy person this will be adjusted by an increase in ventilation

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83
Q

what fraction of the concentration of H in comparison to Na

A

one millionth

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84
Q

what allows the kidney to produce urine of varying concentrations

A

counter current multipliers of juxtamedullary nephrons

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85
Q

describe the efferent arterioles of the glomerulus

A

long and narrow, increasing friction and resistance for fluid (causing a build up of pressure in the glomerulus and inhibiting free outflow of blood)

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86
Q

in hypovolaemia what happens to the hydrostatic pressure in peritubular capillaries

A

reduced - efferent arteriole constriction by angiotensin II

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87
Q

what is the equation for the buffer dibasic phsophate

A

HPO4 + H –> H2PO4 (monobasic)

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88
Q

once urien has left the kidneys, does its composition change

A

no

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89
Q

what can cause a metabolic acidosis

A
  • increased H production eg DKA, lactic acidosis, acetoacetic acid
  • failure to excrete normal load of H eg renal failure
  • loss of HCO3 eg diarrhoea
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90
Q

in hypovolaemia what happens to the oncotic pressure in peritubular capillaries

A

increased - loss of salt and water increases the concentration of plasma proteins

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91
Q

where is the hypertonic medullary gradient established

A

loop of henle in the medulla

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92
Q

which hormone does the increase in renin increase production of

A

angiotensin II

93
Q

why is there no change in anion gap when HCO3 is lost from the gut in metabolic acidosis

A

compensated by increase in Cl

94
Q

what are the main functions of the proximal tubule

A

65-75% NaCl & H20 reabsorbed
all important substances reabsorbed - glucose, AA, FAs
major site of tubular secretion

95
Q

what is the plasma concentration of Na

A

142 mmoles/L

96
Q

how much urine is excreted every day

A

1-2 L

97
Q

what 2 things cause and acidosis to occur (metabolic/ respiratory)

A

respiratory - Increase in PCO2

metabolic - Decrease in HCO3

98
Q

how does the body cope with an acute metabolic acidosis

A

stimulates ventilation so that PCO2 falls (can reach 30L/ min when pH falls to 7)

99
Q

what is responsible for creating the interstitial gradient in the loop of henle

A

active transport of NaCl of ascending limb

100
Q

if ADH is present, what happens to water in the collecting duct

A

leaves it so less urine is lost and more is added to ECF

101
Q

which of the starlings forces favour filtrations

A

hydrostatic pressure (fluid out a vessel)

102
Q

what are the 2 main physiological processes in the renal response to a low ECF

A

reduced atrial pressure

Increased sympathetic discharge (carotid baroreceptors stop inhibition)

103
Q

what is the pressure of the glomerular capillaries dependent on

A

afferent and efferent arteriole diameter and the balance of resistance between them

104
Q

where is K primarily reabsorbed

A

proximal tubule

105
Q

in hypovolaemia, what effect does a reduction in carotid sinus baroreceptor inhibition of sympathetic discharge have

A

increases vasoconstriction
Increased total peripheral resistance
Increases BP

106
Q

where does the majority of metabolic acid get buffered

A

43% in plasma (with HCO3)

57% in cells

107
Q

what does the quantity of carbonic acid in the blood depend on

A

amount of CO2 dissolved in plasma (solubility of CO2 and PCO2)

108
Q

what vessels absorb water from the medullary interstitum

A

vasa recta

109
Q

what 3 factors determine filterability of solutes across the glomerular filtration barrier

A

molecular size, electrical charge, shape

110
Q

how do people live with a chronic respiratory acidosis

A

kidney produces HCO3 to protect pH

acidic conditions stimulate RG formation

111
Q

how long does it take for the entire blood volume to pass through the kidneys

A

<5 mins

112
Q

How does a change in ECF affect ADH secretion

A

increased ECF reduced ADH - more diuresis and reduced reabsorption

113
Q

what is the function of renin

A

cuts angiotensinogen into angiotensin I

114
Q

if you constrict the efferent arteriole, what happens to filtration?

A

increases - reduce blood flow out

115
Q

what is the vasa recta

A

specialised arrangement of peritubular capillaries of the juxtamedullary nephrons (hair pin loops)

116
Q

which type of neurones control sensory innervation of the bladder

A

interneurones (pathways to sensory cortex –> sensation of fullness)

117
Q

why is the blood flow through he vasa recta very slow

A

gives time to equilibrate with the interstiitum

118
Q

is the glucose clearance higher or lower than inulin

A

clearance = 0 - all reabsorbed

119
Q

what reflex is used by paraplegic patients to train themselves to initiate voiding

A

mild mass reflex

e.g pinch skin/ stroke thighs

120
Q

what are 3 basic renal processes

A

filtration
reabsorption
secretion

121
Q

why is GFR useful in measuring renal disease

A

progression of destruction of nephron function decreases GFR (total GFR = sum of all filtration by functioning nephrons)

122
Q

what is the normal plasma osmolarity

A

280-290 mOsm/ kg H20

123
Q

why is the hydrostatic pressure in the peritubular capillaries so low

A

due to hydrostatic pressure overcoming frictional resistance from efferent arterioles

124
Q

in what situation is auto regulation of glomerular capillaries overridden and by what

A

when BP/ blood volume is under serious compromise e.g. haemorrhage
sympathetic vasoconstriction and angiotensin II
(this frees up blood for other organs - up to 800mls/ min)

125
Q

where does the filtrate pass after the glomerulus

A

bowman’s capsule

126
Q

how do hypogastric nerves control micturation

A

sympathetic supply - inhibit bladder contraction

main function is to prevent reflux of semen into bladder during ejaculation (L1-L3

127
Q

Why does the oncotic pressure of the glomerulus increase throughout

A

Become more concentrate when everything but the proteins are filtered out (30 mmHg)

128
Q

which arterioles does angiotensin II constrict at low and high pressures

A

low - efferent

high - both

129
Q

in hypovolaemia, what can cause a hyperglycaemic coma

A

osmotic diuresis

130
Q

what percentage of the filtrate can be reabsorbed in the proximal tubule during a volume deficit

A

75% - increased oncotic pressure

131
Q

what do starling forces favour in the vasa recta

A

reabsorption - high oncontic pressure due to high concentration of particles and tight renal capsule which drives fluid into capillaries

132
Q

how does alcohol affect ADH secretion

A

suppress release from pituitary - absorb less fluid and pee out more (leading to dehydration)

133
Q

What is the function of a buffer

A

minimise changes in pH when H ions are added or removed

134
Q

what is the osmolarity concentration of the distal tubule

A

100 mOsmol (more dilute than the plasma)

135
Q

what does angiotensin II do in the body response to hypovolaemia (4)

A
  • stimulates aldosterone to increase NaCl and H20 reabsorption
  • vasoconstrictor (increases TPR)
  • acts on hypothalamus to stimulate ADH secretion
  • stimulates this mechanism and salt appetite
136
Q

what 2 things cause and alkalosis to occur (metabolic/ respiratory)

A

respiratory - decrease in PCO2

metabolic - increase in HCO3

137
Q

what molecules are regulated by Tm / carrier mediated transport

A

glucose, amino acids, organic acids, PO4, SO4

138
Q

what is the major adaptive response to an acid load and what does it do

A

ammonium excretion

generates new HCO3 and excretes H

139
Q

what percentages of H20, glucose, Na and urea are reabsorbed within the tubules

A

H20 - 99%
glucose - 100%
Na - 99.5%
urea - 50%

140
Q

which of starlings forces is greater at the glomerular capillaries

A 
hydrostatic pressure (Pgc > pie) 
only filtration occurs
141
Q

what are the 3 mechanisms of reabsorption

A

carrier mediated transport system
Active transport of Na
tubular secretion

142
Q

how does aldosterone affect K secretion

A

increases at distal tubule (K lost)

143
Q

what pathways are set up during potty training

A

voluntary initiation pathways

144
Q

what must a solute be to impact ADH secretion

A

an affective osmole - Na etc

urea, glucose etc are ineffective

145
Q

what is the net production of H per day

A

50-100 mmoles per day

146
Q

What substances are removed from the body by secretion

A

harmful - drug metabolites, K, H,

protein bound

147
Q

How is Cl reabsorbed in the proximal tubule

A

diffuse passively down electrochemical gradient established by Na active transport

148
Q

What constituents fo plasma flow are not filtered

A

RBCs

Proteins bigger than albumin

149
Q

what is the average hydrostatic pressure fo the glomerulus

A

55 mmHg

150
Q

what is a metabolic acidosis due to

A

decreased HCO3 from increased H buffering or direct loss of HCO3

151
Q

what 2 things inhibit renin release

A

angiotensin II feedback

ADH

152
Q

what is the minimum concentration of urine produce by the kidneys

A

30-50 mOsmoles/ L

153
Q

what is the metabolic source of H

A

inorganic - S containing amino acids and phoshpholipids

organic - fatty acids, lactic acid (approx 50-100 mmoles H a day)

154
Q

how does the renal tubule respond to an increase in K concentration

A

increase K secretion to decrease intracellular K

155
Q

where is ADH synthesised

A

supraoptic (SO) and paraventricular (PVN) nuclei of the hypothalamus of the brain

156
Q

describe the afferent arterioles of the glomerulus

A

wide and short with little resistance to flow

lots of blood pushed into the glomerulus at a high hydrostatic pressure

157
Q

what is the pCO2 in blood

A

40 mmHg (36- 44)

158
Q

what is the primary control of ADH secretion

A

increase in plasma osmolarity

159
Q

if you constrict the afferent arteriole, what happens to filtration?

A

decreases - lower pressure in glomerulus

160
Q

what can be given in a high acidosis to prevent hyperkalaemia

A

Ca gluconate

161
Q

what feature of renal vasculature keeps BF and GFR constant

A

autoregulation - intrinsic ability to adjust resistance in response to changes in a retrial BP

162
Q

where in the nephron does ionic regulation occur

A

distal tubule

163
Q

what is the half life of ADH and why is this

A

10 minutes - can rapidly adjust to the body needs for water conservation

164
Q

what is different about ammonium excretion in the distal and proximal tubules

A

proximal - Na/ NH4 exchanger - NH4 is formed within the cell

165
Q

why is the anion gap increased in a lactic /diabetic metabolic acidoses

A

reduction in HCO3 is replaced by other anions like lactate etc.

166
Q

are carrier mediated secretory mechanisms specific

A

no
eg. lactic/ uric acid, penicillin, aspirin, PAH same
choline, creatinine, morphine atropine same

167
Q

what is the biggest factor that affects GFR

A

Pressure of the glomerular capillaries (Pgc)

168
Q

what is kussmaul breathing

A

hyperventilation in response to metabolic acidosis

169
Q

what creates the osmotic force in the proximal tubules that drives H20 out

A

active transport of Na and Cl out

increases concentration of solutes inside tubules - glucose, urea

170
Q

why does an increase in H in the ECF increase ventilation

A

drive equation to the right - increased carbonic acid formation and water and CO2
ventilation is then increased to blow off the extra CO2

171
Q

what are causes of an acute respiratory acidosis

A

obstruction of major airways

drugs which depress medullary respiratory centres - opiates/ barbiturates

172
Q

when using dibasic phosphate as a buffer, what is the source of the new HCO3

A

CO2 indirectly from blood

process depends on PCO2

173
Q

what are the 2 main affects of angiotensin II on the tubules

A
  • increases aldosterone production which increases NaCl and H20 reabsorption in DISTAL tubule
  • increases NaCl and H20 reabsorption in PROXIMAL tubule
174
Q

what is the gold standard for measuring plasma clearance and why

A

inulin clearance - freely filtered/ no kidney metabolism

IV loading dose and sample plasma / urine

175
Q

which of the starlings forces favours reapsorption

A

oncotic pressure

176
Q

what is the function of ADH/ vasopressin

A

control how concentrated the urine is

177
Q

what is the total body water distribution in the body (42 L)

A

1/3 ECF (14L) - Plasma (3L), Interstitial fluid (11L)

2/3 ICF - intracellular fluid (28L)

178
Q

what its the average daily GFR

A

180 L/ day

179
Q

what is the ratio of bicarbonate (HCO3) to carbonic acid (H2CO3)

A

20 : 1

180
Q

what is the relationship between the rate of ADH secretion and rate of discharge from stretch receptor afferents

A

inverse

181
Q

What does a decreased delivery of NaCl to the macula densa do to renin release

A

increase renin release

182
Q

what is the site of water regulation

A

collecting duct

183
Q

what determines body water between cells and ECF

A

osmotically active particles - Na and Cl (major ECF osmoles)

184
Q

what cells produce the hormone renin and where are they found

A

juxtaglomerular cells

smooth muscle cells of the media of the afferent arteriole

185
Q

what are causes of an acute respiratory alkalosis

A

voluntary hyperventilation
aspirin
first ascent to altitude

186
Q

why does volume consideration take primacy over osmolarity if ECF is compromised

A

save perfusion to the brain

187
Q

how is urine removed form the male and female urethra

A

male - contractions of the bulbocavernous muscle

female - gravity

188
Q

what percentage of Na reabsorption occurs in the proximal tubule

A

65-75%

active transport establishes a gradient for Na across wall

189
Q

which tubule is dibasic phosphate used as a buffer and what does it produce

A

distal

generates new HCO3 and excretes H

190
Q

if a substance has a higher clearance that inulin what will happen

A

filtered and secreted

[Ux] higher, [Px] lower

191
Q

why does aldosterone cause a weight gain

A

retention of H20 and water

volume expands until ANP causes natural diuresis

192
Q

which 3 nerves control motor innervation of micturition

A

pelvic - parasympathetic
hypogastric - sympahtetic
pudendal - somatic motor neurones

193
Q

How is the electrocehmical gradietn for Na reabsorption established

A

Na/K ase - 3 Na for 2 K - gradient drives Na out the cell

194
Q

what is respiratory alkalosis a result of

A

fall in PCO2 from increased ventilation and CO2 blow off

195
Q

what creates the fluid pressure of the glomerulus (hydrostatic)

A

pressure created by fluid in Bowman’s capsule

196
Q

where in the loop of henle is the fluid most concentrated

A

at the bottom, in between descending and ascending limbs

197
Q

where does the bulk of HCO3 reabsorption occur

A

proximal tubule

198
Q

what is Tm

A

the max capacity of a carrier mediated transport system

199
Q

what 4 factors affect GFR

A

pressure of glomerular capillaries
sympathetic vasoconstriction nerves
circulating catecholamines (constrict mostly afferent)
Angiotensin II

200
Q

how does the body respond to severe vomiting (hypovolaemia and metabolic acidosis)

A

stimulate aldosterone to increase distal tubule Na reabsorption (H ion exchange as Cl is lost)
Increase PCO2 to drive H secretion
- this exacerbates the metabolic acidosis but restoring volume is more important

201
Q

how does the kidney respond to chronic respiratory alkalosis

A

reduces HCO3 by reabsorptive mechanism - lost in urine

202
Q

Why is glomerular capillary pressure higher than in most other capillaries fo the body

A

Afferent arterioles have a high hydrostatic pressure and efferent arterioles cause a build up of pressure in glomerulus

203
Q

what is the golden rule of circulation

A

if you have a high resistance, hydrostatic pressure upstream is increased, while the pressure downstream is decreased

204
Q

Where does the majority of reabsorption occur

A

distal and proximal tubule

205
Q

what is the titratable acidity

A

measure of the amount of NaOH needed to titrate urine back to a pH of 7.4 for a 24 hour sample

206
Q

why does buffering of H by intracellular buffers cause a change in electrolytes

A

in RBC - accompanied by Cl

exchanged for K

207
Q

What is the plasma concentration of K

A

4 mmoles/L

208
Q

what are causes of a chronic respiratory alkalosis

A

long term residence at altitude

low PO2 <60 mmHg - peripheral chemoreceptors increase ventilation

209
Q

how much HCO3 if filtered per day

A

4320 mmoles - all reabsorbed

180 x 24

210
Q

what is the average GFR

A

125 mls/min

211
Q

what is the rate limiting step int eh production of angiotensin II

A

release of renin (angiotensinogen is always present in plasma)

212
Q

is the penicillin clearance higher or lower than inulin

A

higher - filtered and secreted

213
Q

what makes the border of the proximal tubule have a higher permeability to Na ions

A

enormous surface area from microvilli

large number of Na ion channels

214
Q

which input responses increase ADH secretion

A

pain, emotion, stress, exercise, nicotine, morphine, traumatic surgery TO RETAIN FLUID

215
Q

what is respiratory acidosis a result of

A

reduced ventilation - retention of CO2

216
Q

if molecules X has filtration > excretion what will be the renal handling of X

A

net reabsorption

217
Q

what is the normal GFR in a 1.73m^2

A

100 mls/ min

218
Q

which hormone controls distal tubule Na reabsorption

A

aldosterone

219
Q

what happens int he descending limb of the loop of henle

A

fluid flows down

relatively impermeable to NaCl

220
Q

what are causes of a chronic respiratory acidosis

A

lung disease - bronchitis, emphysema, asthma

221
Q

what hormone regulates K secretion

A

aldosterone

222
Q

what are the main intracellular buffers

A

Proteins, organic and inorganic phosphates, haemoglobin in erythrocytes

223
Q

what is the minimum obligatory loss of H20 each day and why

A

500 mls - urea, SO4, PO4, ammonia, non waste ions (Na and K)

224
Q

what are the functions of the vasa recta

A

provide oxygen for medulla
don’t disturb interstitial gradient
remove volume from the interstitial

225
Q

if blood pressure drops, what happens to Na active transport

A

reduces

226
Q

where is ADH release from

A

posterior pituitary

227
Q

what is the average blood flow to the kidneys

A

1200 mls/ min (20-25% of CO)

228
Q

what happens to a substrate if it is present in concentrations higher than Tm

A

excreted in the urine

urinary system (2 decks)

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