Physiology Flashcards
(262 cards)
1
Q
what is osmolarity?
A
the concentration of osmotically active particles present in a solution
2
Q
what 2 factors are needed to calculate osmolarity?
A
- the molar concentration of the solution
2. the number of osmotically active particles present
3
Q
what is tonicity?
A
the effect a solution has on cell volume
4
Q
what will an isotonic solution do to cell volume?
A
no change
5
Q
what will a hypertonic solution do to cell volume?
A
decrease in cell volume
6
Q
what will a hypotonic solution do to cell volume?
A
increase in cell volume
7
Q
what does tonicity take into consideration that osmolarity doesnt?
A
the ability of the solute to cross the cell membrane
8
Q
compare percentage of total body water to body weight in males and females?
A
males- 60% of body weight
females 50% of body weigh
9
Q
what are the 2 major compartments that make up total body water? (and the percentage of each)
A
intracellular fluid 67%
extracellular fluid 33%
10
Q
what are the main 2 compartments that make up the extracellular fluid? (and the percentage of each)
A
plasma 20%
interstitial fluid 80%
11
Q
what separates the extracellular fluid and the intracellular fluid?
A
plasma membrane
12
Q
how do we measure body fluid compartments clinically?
A
tracers
13
Q
what tracer allows us to determine the total body water?
A
3 H20
14
Q
what tracer allows us to determine the volume of extracellular fluid?
A
inulin
15
Q
what tracer allows us to determine the volume of plasma?
A
labelled albumin
16
Q
is sodium higher intracellularly or extracellularly?
A
extracellularly
17
Q
is potassium higher intracellularly or extracellularly?
A
intracellularly
18
Q
is chloride higher intracellularly or extracellularly?
A
extracellularly
19
Q
what separates the plasma from the interstitial fluid?
A
capillary wall
20
Q
what are the main ions in the ECF?
A
Na+
Cl-
HCO3-
21
Q
what are the main ions in the ICF?
A
K+
Mg2+
negatively charged proteins
22
Q
what is the osmotic concentration of the ECF?
A
roughly 300 mosmol/l
23
Q
what is the osmotic concentration of the ICF?
A
roughly 300 mosmol/l
24
Q
urea is the biproduct of the breakdown of what substance?
A
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
