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Flashcards in Physiology Deck (262):
1

what is osmolarity?

the concentration of osmotically active particles present in a solution

2

what 2 factors are needed to calculate osmolarity?

1. the molar concentration of the solution
2. the number of osmotically active particles present

3

what is tonicity?

the effect a solution has on cell volume

4

what will an isotonic solution do to cell volume?

no change

5

what will a hypertonic solution do to cell volume?

decrease in cell volume

6

what will a hypotonic solution do to cell volume?

increase in cell volume

7

what does tonicity take into consideration that osmolarity doesnt?

the ability of the solute to cross the cell membrane

8

compare percentage of total body water to body weight in males and females?

males- 60% of body weight
females 50% of body weigh

9

what are the 2 major compartments that make up total body water? (and the percentage of each)

intracellular fluid 67%
extracellular fluid 33%

10

what are the main 2 compartments that make up the extracellular fluid? (and the percentage of each)

plasma 20%
interstitial fluid 80%

11

what separates the extracellular fluid and the intracellular fluid?

plasma membrane

12

how do we measure body fluid compartments clinically?

tracers

13

what tracer allows us to determine the total body water?

3 H20

14

what tracer allows us to determine the volume of extracellular fluid?

inulin

15

what tracer allows us to determine the volume of plasma?

labelled albumin

16

is sodium higher intracellularly or extracellularly?

extracellularly

17

is potassium higher intracellularly or extracellularly?

intracellularly

18

is chloride higher intracellularly or extracellularly?

extracellularly

19

what separates the plasma from the interstitial fluid?

capillary wall

20

what are the main ions in the ECF?

Na+
Cl-
HCO3-

21

what are the main ions in the ICF?

K+
Mg2+
negatively charged proteins

22

what is the osmotic concentration of the ECF?

roughly 300 mosmol/l

23

what is the osmotic concentration of the ICF?

roughly 300 mosmol/l

24

urea is the biproduct of the breakdown of what substance?

protein

25

bilirubin is the biproduct of the breakdown of what substance?

haemoglobin

26

what hormone is released by the kidney in response to hypoxia?

erythropoetin

27

uric acid if the biproduce of the breakdown of what substances?

purines
eg adenosine, guanine

28

what is the active form of vitamin D?

calcitriol

29

what is the function of calcitriol?

promotes Ca++ absorption in the GI tract

30

how many OH hydroxyl groups are added to vit D in order to convert it to calcitriol?

2 hydroxyl groups

31

where is the first hydroxyl group added to vitamin D? (a step in the conversion to calcitriol)

liver

32

where is the second hydroxyl group added to vitamin D? ( a step in the conversion to calcitriol)

kidneys

33

what percentage of cardiac output goes to the kidneys?

25%

34

what are the 2 types of nephron? (and give percentages of each)

cortical 80%
juxtamedullary 20%

35

compare the loop of Henle's in the cortical and juxtamedullary nephrons?

juxtamedullary nephron loop of Henle is much longer and extends right down into the medulla, cortical nephron is shorter and only extends slightly into the medulla

36

compare the capillaries which surround the renal tubules of the cortical and juxtamedullary nephrons?

juxtamedullary nephron- efferent arteriole becomes a single capillary called the vasa recta
cortical nephron- efferent arteriole becomes a network of capillaries called the peritubular network

37

compare the diameter of the afferent and efferent arterioles?

afferent arteriole has a bigger diameter

38

how much plasma of the afferent arteriole is filtered into the bowman's capsule?

20%

39

what cells is renin secreted from?

granular cells (juxtaglomerular cells) wichin the juxtaglomerular apparatus

40

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

rate of filtration = plasma conc of substance x GFR

41

what is the normal GFR?

125ml/min
0.125l/min

42

what happens to the rate of filtration of a substance as the concentration of the substance in plasma increase?

rate of filtration increases

43

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

rate of excretion = urine conc of substance x urine flow rate

44

how do you calculate the rate of reabsorption of a substance?

rate of filtration - rate of excretion

45

what is the normal urine flow rate?

1ml per minute
0.001l per minute
(very variable depending on body conditions)

46

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

rate of excretion - rate of filtration

47

collectively, what is the glomerular capillary endothelium, basement membrane and podocyte layer called?

glomerular membrane

48

what net charge does the basement membrane of the glomerular membrane have?

negative charge

49

what is the function of the negatively changed basement membrane of the glomerular membrane?

repels large negatively charged proteins

50

what are the 4 starling forces that compromise net filtration pressure at the glomerulus?

glomerular capillary blood pressure
bowmans capsule hydrostatic pressure
capillary oncotic pressure
bowmans capsule oncotic pressure

51

which is the starling force which contributes most to the net filtration pressure at the glomerulus?

glomerular capillary blood pressure

52

how do you calculate the net filtration pressure of the glomerulus?

(glomerulus capillary blood pressure + bowmans capsule oncotic pressure)
-
(bowmans capsule hydrostatic pressure + capillary oncotic pressure)

53

why, unlike most capillaries, is the glomerular capillary blood pressure constant from afferent arteriole to efferent arteriole?

because as you lose volume the diameter decreases
--> pressure is maintained

54

what solutes determine oncotic pressure?

plasma proteins

55

since there should be no plasma proteins within the lumen of the bowman's capsule, what should the bowmans capsule oncotic pressure be?

0 mmHg

56

what is the glomerular filtration rate?

the rate at which protein=free plasma is filtered from the glomeruli into the bowman's capsule per unit time

57

how do you calculate the gfr?

Kf x net filtration pressure

where Kf = filtration coefficient

58

what is the main determinant of GFR?

glomerular capillary blood pressure

59

what are the 2 main ways of glomerular filtration rate regulation?

intrinsic control
extrinsic control

60

which nervous system is involved in the extrinsic control of GFR and via what reflex?

sympathetic control via baroreceptor reflex

61

what are the 2 types of intrinsic autoregulation of GFR?

myogenic mechanism
tubuloglomerular feedback mechanism

62

what does vasoconstriction of the afferent arteriole do to the GFR?

decreases the GFR

63

what does vasodilation of the afferent arteriole do to the GFR?

increases the GFR

64

explain why a fall in blood pressure might cause reduced GFR? (external regulation)

reduced BP detected by baroreceptors
sympathetic activity is increased
generalised arteriolar vasoconstriction (afferent arteriole)
reduced glomerular capillary BP so reduced GFR and urine volume
[helps to compensate for fluid loss]

65

broadly speaking, why do systemic arterial blood pressure changes not always causes changed in GFR?

intrinsic control of the GFR (autoregulation)

66

what is myogenic autoregulation of GFR?

if vascular smooth muscle is stretched (due to increased BP) it contracts thus constricting the afferent arteriole

67

what is tubuloglomerular feedback autoregulation of GFR?

If the NaCl increases (happens when GF is raised) within the juxtaglomerular apparatus raises, the macula densa sense it and cause the afferent arteriole to constrict

68

why might a kidney stone cause reduced GFR?

increased hydrostatic pressure which opposes filtration

69

why might severe diarrohea cause reduced GFR?

dehydration leads to increased plasma protein concentration (ie bigger capillary oncotic pressure which opposes filtration)

70

why might severely burned patients have an increased GFR?

plasma proteins are lost from site so leads to decreased plasma protein concentration (ie smaller capillary oncotic pressure)

71

why might kidney damage cause decreased GFR?

might decrease filtration coefficient leading to decreased GFR

72

what is plasma clearance?

the volume of plasma completely cleared of a particular substance per minute

73

what are the units of plasma clearance?

ml per min
ml/min

74

how do you calculate clearance of a substance?

rate of excretion/ plasma concentration

75

what is the inulin clearance rate?

125ml/min

76

is inulin absorbed by the renal tubules?

no

77

is inulin secreted by the renal tubules?

no

78

the clearance of which substance is much more convenient to determine GFR from than inulin?

creatinine clearance

79

why is creatinine clearance not as accurate as inulin clearance as an indicator of GFR?

because some is secreted in the tubules

80

what is the rate of glucose clearance?

0ml/min

81

why might the clearance of a substance be 0?

1. filtered, all reabsorbed, no tubular secretion
2. not filtered no tubular secretion

82

is urea reabsorbed in the renal tubules?

partly

83

is urea secreted in the renal tubules?

no

84

what is the range of values for clearance of a substance which is partly reabsorbed but not secreted?

Less than 125ml/min

85

what is the range of values for clearance of a substance which is secreted but not reabsorbed?

>125ml/min
because clearance is bigger than GFR

86

is hydrogen reabsorbed in the renal tubules?

no

87

is hydrogen secreted in the renal tubules?

yes

88

if the clearance of a substance is lower than the GFR, what does this indicate?

the substance is reabsorbed in the renal tubulres

89

if the clearance of a substance is the same as the GFR, what does this indicate?

the substance is neither reabsorbed or secreted

90

if the clearance of a substance is the higher than the GFR, what does this indicate?

the substance is secreted into the tubules

91

the clearance of what substance indicates the renal plasma flow?

clearance of para-amino hippuric acid (PAH)

92

why is clearance of PAH used to measure renal plasma flow?

filtered freely at glomerulue and is completely secreted in the renal tubules, none is reabsorbed

93

creatinine a biproduct of the breakdown of what?

muscle

94

what is the clearance of PAH?

650ml/min

95

what is the renal plasma flow?

650ml/min

96

how do you calculate the filtration fraction?

GFR/renal plasma flow

97

what is the filtration fraction?

20%

98

what is haemocrit?

packed cell volume
--> volume percentage of red blood cells in blood

99

how doyou calculare renal blood flow?

renal plasma flow / (1-haemocrit)

100

what is the average renal blood flow?

1200ml/min

101

compare transcellular and paracellular absorption?

transcellular- absorption across the cell of the tubular wall
paracelular- absorption across spaces in the cells of the tubular wall

102

what is required for primary active transport to occur?

ATP

103

what ion is secondary active transport usually coupled to the movement of?

Na+ down its conc gradient

104

what membrane (apical or basolateral) is the Na/K/ATPase pump exclusively found on?

basolateral membrane

105

the Na/K/ATPase requires the hydrolysis of what?

ATP

106

why is it important that the Na/K pump keeps pumping Na out of the cells lining the proximal convoluted tubule?

keeps intracellular conc of Na low which allows Na to diffuse from the lumen into the cell down a conc gradient

107

the secondary active transporter on the apical membrane of the cells in the proximal convoluted tubule transports what ion across the membrane into the lumen in replace for Na?

H+

108

why does Cl- from the lumen of the proximal convoluted tubule follow Na+ into the interstitial fluid of the cells lining the tubule wall?

postively charged Na influx sets up an electrochemical gradient for negatively charged Cl- to follow

109

does Cl- get reabsorbed from the proximal convoluted tubule transcellularly or paracellularly?

paracellularly

110

why does H2O from the lumen of the proximal convoluted tubule follow NaCl into the interstitial fluid of the cells lining the tubal wall?

NaCl sets up an osmotic gradient for water to follow

111

does H2O get reabsorbed from the proximal convoluted tubule transcellularly or paracellularly?

paracellularly

112

why has the oncotic pressure of the vasa recta increased since the afferent arteriole?

same number of protiens as before but 20% of plasma has gone
--> increased conc of plasma proteins

113

how does glucose get reabsorbed over the apical membrane from the proximal convoluted tubule lumen?

Na/Glucose cotransporter
(symport)

114

how does glucose get across the basolateral membrane of the cells lininc the proximal convoluted tubule?

facillitated diffusion

115

what happens when the glucose transporter mechanisms in the proximal convoluted tubule become saturated?

not all glucose can be reabsorbed
--> glucose in urine

116

why might there be more glucose present than space on the glucose transporter mechanisms?

high blood glucose eg diabetes mellitus

117

the tubular fluid is 'iso-osmotic' when it leaves the proximal convoluted tubule, why?

because both salt and water (in correlating amounts) have been reabsorbed

118

the tubular fluid is 'iso-osmotic' when it leaves the proximal convoluted tubule? what does this mean?

same osmolarity as the plasma
(300mosmol/l)

119

what is reabsorbed in the ascending limb of the loop of henle?

Na+ and Cl-
no water

120

compare the thin ascending limb and thick ascending limb of the loop of henle in terms of how the salt is reabsorbed?

thick ascending limb: active transport
thin ascending limb: passive transport

121

what is reabsorbed in the descending limb of the loop of henle?

water
no NaCl

122

why is the ascending limb of the loop of henle impermeable to water?

very tight junctions so H2O can't follow osmotic gradient (remember it moves paracellularly)

123

what ions does the triple co-transporter found on the ascending limb of the loop of henle reabsorb?

Na+
K+
2Cl-

124

what drug blocks the triple co-transporter found on the ascending limb of the loop of henle?

loop diuretics

125

why does water reabsorb in the descending limb of the loop of henle?

follows the osmotic gradient created by the interstitial fluid
(originally created by the reabsorption of salt from ascending limb)

126

is the fluid leaving the ascending limb of the loop of henle hypo-osmotic, iso-osmotic or hyper-osmotic?

hypo-osmotic

127

is urea actively or passively reabsorbed in the loop of henle?

passively

128

what is countercurrent multiplication?

the reabsorption of NaCl and urea from the ascending loop of Henle followed by the reabsorption of water from the descending loop of Henle making the corticomedullatry gradient

129

what is the purpose of the countercurrent multiplication?

to enable the kidney to produce different volumes and concentrations of urine according to the amounts of ADH

130

what happens to the osmolairity of the vasa recta as it dips down into the medulla? and why?

osmolairity increases as the fluid equilibrates with the corticomedullary gradient
water loss
solute gain

131

what happens to the osmolarity of the vasa recta as it ascends back to the cortex? and why?

osmolarity decreases as the fluid equilibrates with the corticomedullary gradient
water gain
solute loss

132

why is the vasa recta in a hairpin loop?

prevents the washing away of solutes
(as on its ascent it losses solutes and gains water)

133

compare the osmolairities of the blood entering and leaving the vasa recta?

same osmolarity
300mosmol/l

134

what acts as the countercurrent exchanger?

the vasa recta

135

what makes up the countercurrent system?

countercurrent multiplier and countercurrent exchanger
ie loop of henle plus vasa recta

136

what is the osmolarity of the tubular fluid entering the distal tubule?

100mosmol/l
hypo-osmotic

137

what parts of the nephron are within the corticomedullary gradient?

loop of henle
collecting ducts

138

what parts of the nephron do hormone influence?

distal convoluted tubule
collecting ducts

139

what does ADH cause the reabsorption/secretion of?

increased reabsorption of water

140

what does aldosterone cause the reasbsorption/secretion of?

increased reabsorption of Na
increased secretion of K

141

what does atrial natriureteric peptide cause the reabsorption/secretion of?

decreased reasborption of Na

142

what does parathyroid hormone cause the reabsorption/secretion of?

increased calcium reabsorption
decreased phosphate reabsorption

143

how do you calculate pH from [H+]?

pH = log (1/[H+])

144

what is the pH of arterial blood?

7.45

145

what is the pH of venous blood?

7.35

146

what is the average pH of blood?

7.40

147

what happens to the pH as [H+] increases?

pH decreases

148

compare acidosis and alkalosis in terms of what they do to the nervous system?

acidosis can lead to CNS depression
alkalosis can lead to PNS and CNS overexcitability

149

what does increased plasma [H+] do to the amount of K+ secreted in the renal tubules?

decreases K+ secretion
(retention)

150

what are the 3 sources of H+ addition?

carbonic acid formation
inorganic acids produced from nutrient breakdown
organic acids produced from metabolism

151

what molecules form carbonic acid?

CO2 + H2O

152

what does carbonic acid dissociate into?

H+ + HCO3-

153

compare strong and weak acids in terms of dissociation in solution?

strong acids dissociate completely in solution
weak acids dissociate partially in solution

154

what is a buffer system?

a pair of substances, one can yield free H+ when the [H+] decreases, the other can take free H+ when the [H+] increases in order to maintain pH

155

what is the first line defence to any change in pH/acid status?

buffer system

156

within the HA = H+ + A- buffer system, which molecule can yield free H+ when the [H+] decreases?

HA

157

within the HA = H+ + A- buffer system, which molecule can mop up free H+ when the [H+] increases?

A-

158

if H+ is added to the HA= H+ + A- system, what happens to the equilibrium and levels of each molecule?

equilibrium is shifted to the left

[HA] increases
[A-] decreases
[H+] remains the same

159

if base (B-) is added to the HA = H+ + A- system, what happens to the equilibrium and the levels of each molecule?

equilibrium shifts to the right

[HA] decreases
[A-] increases
[H+] remains the same

160

how do you calculate the dissociation constant of a weak acid?

K = ( [H+] [A-] )/ [HA]

161

how do you calculate pK using the dissociation constant (K)?

pK = -log K

162

what is pK?

the pH at which a particular chemical reaction will be at equilibrium

163

what does the henderson-hasselbalch equation calculate?

the pH

164

what is the henderson-hasselbalch equation?

pH = pK + log( [A-] / [HA] )

165

what is the most important physiological buffer system?

the CO2 - HCO3 buffer

166

what is the CO2 - HCO3 buffer?

CO2 + H2O = H2CO3 = H+ + HCO3-

167

formation of carbonic acid from carbon dioxide and water is catalysed by what enzyme?

carbonic anhydrase

168

what is the pK for carbonic acid?

pH at equilibrium (pK) = 6.1

169

what controls the [HCO3-] of plasma?

the kidneys

170

what controls the PCO2 of plasma?

the lungs

171

why might the renal vain have a higher [HCO3-] than the renal artery?

because the kidneys can add new HCO3- to the blood

172

what does the reabsorption of filtered HCO3- and the addition of new HCO3- to the renal vein depend on?

H+ secretion into the renal tubule

173

how does reabsorption of HCO3- occur in the proximal tubule?

indirectly
H+ is secreted into tubule, this binds with HCO3- to form carbonic acid which forms carbon dioxide and water. This readily diffuses across the apical membrane into the cell.

174

what happens to the carbon dioxide and water which enters the tubular cell? (formed from H+ and HCO3- in the renal tubule)

forms carbonic acid and then dissociates into HCO3- and H+

175

where in the nephron is HCO3- reabsorbed?

proximal tubule

176

how does HCO3- leave the basolateral membrane of the tubular cell?

Na/HCO3 cotransporter

177

how doe H+ leave the apical membrane of the tubular cell in the proximal tubule in order to bind with HCO3-?

Na/H antiporter

178

what drives the secretion of H+ through the apical membrane of the tubular cell? in order to bind with HCO3-

CO2 partial pressure

179

what happens to the H+ that is transported across the apical membrane into the tubular fluid when all the HCO3- has already been absorbed?

binds to phosphate to form acid phosphate and is excreted

if even more H+
binds to ammonia to form ammonium and is excreted

180

what 2 ways does titratable acid and ammonium excretion increase the pH of the plasma?

loss of H+ ions
gain of HCO3-

(simultaneously rids body of acid and regenerates buffer stores)

181

what is the maximum amount of titratable acid that can be excreted and therefore the maximum amount of new HCO3- that can be gained through this way?

40mmol/day titratable acid
40mmol/day new HCO3-

182

ammonia is formed from the breakdown of what in the tubular cells?

glutamine

183

what enzyme breaks glutamine down to ammonia?

glutaminase

184

how is ammonia transported across the apical membrane into the tubular fluid?

diffusion

185

for every H+ excreted as acid phospate, how many new HCO3- have been formed?

1

186

for every H+ excreted as ammonium, how many new HCO3- have been formed?

1

187

in what pH state will titratable acid and ammonium be excretion be increased?

acidosis

188

what is the normal range of [HCO3-] of the plasma? (and the usual value?)

23-27mmol/l
24mmol/l

189

what is the normal range of PCO3 of the plasma? (and the usual value?)

35-45mmHg
40mmHg

190

compare compensation and correction of acid base disturbances?

compensation: restoration of pH irresepctive of what happens to [HCO3- ]and PCO2

correction: restoration of pH, [HCO3-] and PCO2

191

why can buffer stores not always completely compensate for acid base disturbances?

stores become depleted

192

what organ has a role in restoring free bicarbonates invovled in buffering?

kidney

193

respiratory acidosis drives the carbonic equlibrium to which side?

to the right

194

what happens to the [H+] and [HCO3-] in respiratory acidosis?

both increase

195

what indicates uncompensated respiratory acidosis?

pH below 7.35 and CO2 above 45mmHg

196

why is more HCO3- reabsorbed/made in the kidneys in respiratoy acidosis?

high PCO2 drives H+ secretion into the tubular fluid which drives HCO3- reabsorption/production

197

how does the kidney compensate for respiratory acidosis?

excretes acid
increases [HCO3-] of plasma

198

what mechanism corrects respiratory acidosis?

restoration of normal ventilation

199

in respiratory acidosis, what does the renal compensatory system do to [H+] and [HCO3-]?

[H+] decreases
[HCO3-] increases further

200

what is respiratory alkalosis?

excess removal of CO2 from the body

201

what is respiratory acidosis?

retention of CO2

202

what does hyperventilation do to PCO2?

decreases it

203

what does respiratory alkalosis do to the carbonic acid equilibrium?

shifts it to the left

204

what happens to [H+] and [HCO3-] in respiratory alkalosis?

they both fall

205

when is uncompensated respiratory alkalosis indicated?

pH above 7.45 and PCO2 below 35mmHg

206

what does respiratory alkalosis do to the rate of H+ secretion from the kidney tubules?

decreases it

207

what does respiratory alkalosis do to the rate of HCO3- reabsorption/new production?

decreases reabsorption
no new HCO3- is generated

208

in respiratory alkalosis, what does the renal compensatory system do to [H+] and [HCO3-]?

[H+] is increased
[HCO3-] is decreased further

209

how does correction of respiratory alkalosis occur?

restoration of normal ventilation

210

what does the renal compensatory system do to the pH in respiratory alkalosis?

reduces it
(due to reducing HCO3- and therefore increasing H+ through buffer system)

211

what is the most common of the 4 major acid base disturbances?

metabolic acidosis

212

in metabolic acidosis, what happens to the levels of [H+] and [HCO3-]?

[H+] increased
[HCO3-] decreased

213

what is uncompensated metabolic acidosis indicated by?

pH below 7.35 and [HCO3-] is low

214

how does the respiratory system compensate for metabolic acidosis?

ventilation increases to blow off more CO2

215

in respiratory compensation of metabolic acidosis, what happens to the [H+] and the [HCO3-]?

[H+] decreases
[HCO3-] further decreases

216

why is respiratory compensation for metabolic acidosis? essential when metabolic correction through the kidneys can occur?

respiratory compensation is needed to compensate pH immediately

renal system would take too long to correct

217

how do you correct for metabolic acidosis?

kidneys lose H+ and gain HCO3-

218

what happens to the [H+] and [HCO3-] in metabolic alkalosis?

[H+] decreases
[HCO3-] increases

219

what is uncompensated metabolic alkalosis indicated by?

pH above 7.45 and [HCO3-] is high

220

how does the respiratory system compensate for metabolic alkalosis?

ventilation is slowed

221

how do pH changes signal to change lung ventilation?

through peripheral chemoreceptors

222

what happens to the [H+] and [HCO3-] in respiratory compensation of metabolic alkalosis?

[H+] increases
[HCO3-] further increases

223

how do you correct for metabolic alkalosis?

HCO3- is excreted
(this also increases [H+] due to buffer system)

224

compare correction of resp acidosis/alkalosis to metabolic acidosis/alkalosis?

resp: restoration of normal respiratory function
metabolic: mediated by renal system

225

compare compensation of resp acidosis/alkalosis to metabolic acidosis/alkalosis?

resp: renal system compensates
metabolic: resp system compensates

226

why is respiratory acidosis harder to compenate for than metabolic acidosis?

because renal compensation (for respiratory acidosis) takes far longer than respiratory compensation (for metabolic acidosis)

227

which parts of the nephron are the triple cotransporters found on?

thick ascending limb of the loop of henle
early distal tubule

228

compare the ion permeability of the early and late collecting duct?

late collecting duct has a lower ion permeability

229

what is the half life of ADH?

10-15 minutes

230

what receptors within the cells of the collecting duct does ADH bind to?

type 2 vasopressin receptors

231

what membrane of the cells lining the collecting duct are type 2 vasopressin receptors found on?

basolateral membrane

232

what does the binding of ADH to the type 2 vasopressing receptors do?

increases expression of aquaporins on the apical membrane

233

where are the aquaporins stored when they are not on the apical membrane?

internalised within vesicles and stored in the cytoplasm

234

what does high plasma ADH concentrations do to the tonicity of the urine?

makes it hypertonic

235

what does low plasma ADH concentrations do to the tonicity of the urine?

makes it hypotonic

236

why does opening more aquaporins increase urine osmolarity?

because the fluid within the collecting duct equalises with the corticomedullary gradient meaning lots of water is reabsorbed

237

as ADH concentration within the plasma increases what happens to the urine volume?

decreases

238

as ADH concentration within the plasma decreases what happens to the urine volume?

increases

239

as ADH concnetration within the plasma increases what happens to the total solute excretion?

remains the same

240

what are the 2 main functions of ADH?

H2O reabsorption
arterial vasoconstriction

241

what are the 2 stimulators of the hypothalamus to release ADH?

hypothalmic osmoreceptors
left atrial volume receptors

242

what is the main form of treatment for central diabetes insipidus?

ADH replacement

243

what long term drug side effect can cause diabetes insipidus?

lithium

244

what is the main stimulator of the hypothalamus to release ADH?

hypothalmic osmoreceptors

245

what causes the feed-forward inhibition of ADH?

stimulation of stretch receptors in the upper GI tract

246

what does nicotine do to ADH release?

stimulates

247

what does MDMA do to ADH release?

stimulates

248

what does alcohol do to ADH release?

inhibits

249

what directly stimulates release of aldosterone from the adrenal cortex?

increased K+

250

what indirectly stimulates the release of aldosterone from the adrenal cortex?

decreased Na+ through RAS

251

how much K+ is usually excreted in the urine in the absence of aldosterone and why?

none because it is all reabsorbed

252

from what organ is ACE produced?

lungs

253

what are the 4 functions of angiotensin II?

promote ADH secretion
thirst
arteriolar vasoconstriction
aldosterone

254

what are the 3 stimulatory factors for renin release from the granular cells in the juxtaglomerular apparatus?

1. reduced pressure in the afferent arteriole
2. reduced NaCl sensed by the macula densa
3. increased sympathetic activity (due to low BP)

255

how does aldosterone increase reabsorption of Na?

increases expression of apical Na channels
increases number/activity of basolateral Na/K ATPase
(both in distal and colelcting tubules)

256

where is atrial natriureteric peptide secreted?

atrial muscle cells

257

what stimulates the secretion of ANP?

mechanical stretching of the atrium

258

what are the 2 mechanisms which govern micturation?

1. micturation reflex
2. voluntary control

259

what stimulates the micturation reflex?

stretch in the walls of the urinary bladder

260

what is the earliest expression of diabetic nephropathy?

microalbuminuria

261

what is the most common reason for proteinuria? (broad)

glomerular proteinuria

262

what are the different reasons for proteinuria? (broad sub groups)

overflow
glomerular
tubular
secreted