renal physiology part 1 Flashcards
1
Q
what is osmolarity
A
the concentration of osmotically active particles that are present in a solution
2
Q
what is the units of osmolarity
A
osmol/l or mosmol/l
3
Q
what kind of solutions are body fluids
A
weak salt solutions
4
Q
what 2 factors are needed to calculate osmolarity
A
molar concentration of the solution
the number of osmotically active particles present
5
Q
what is the osmolarity of 150mM NaCl
A
150 x 2 = 300 mosmol/L
6
Q
what are the units of osmolality
A
osmol/Kg of water
7
Q
what is tonicity
A
the effect a solution has on a cell volume
8
Q
what impact does an isotonic solution have on the cell volume
A
no impact
9
Q
what impact does a hypotonic solution have on the cell volume
A
increase in cell volume due to water entering the cell
10
Q
what impact does a hypertonic solution have on the cell volume
A
decrease in cell volume due to water leaving the cell
11
Q
what happens to a red blood cell in a hypotonic solution
A
cell lysis
12
Q
is there movement of water between isotonic solutions
A
yes just not in one net direction
13
Q
what is bilirubin a biproduct of
A
breakdown of haemoglobin
14
Q
what is uric acid a biproduct of
A
breakdown of purines e.g. adenosine and guanine
15
Q
what does tonicity take into accound that osmolarity doesnt
A
the ability of a solute to cross the cell membrane
16
Q
what is urea a biproduct of
A
breakdown of protein
17
Q
will urea cause cell lysis.
why/why not
A
yes
can easily flow across the membrane of red blood cells
18
Q
will sucrose cause cell lysis
why/why not
A
no
it is a very polar molecule so will not pass across the membrane so the cell will not swell
19
Q
is urea hypo/hyper/iso tonic
A
hypotonic
20
Q
is sucrose hypo/hyper/iso tonic
A
isotonic
21
Q
what % of males is water
A
60%
22
Q
what % of females is water
A
50%
23
Q
why do females have lower % body water
A
more fat tissue which contain less water
24
Q
what 2 compartments does TBW exist as
A
intra and extracellular fluid
25
intracellular fluid is what % of TBW
67%
26
extracellular fluid is what % of TBW
33%
27
what is extracellular fluid made up of
plasma
interstitial fluid
lymph (negligable)
transcellular fluid (negligable)
28
what % of the ECF is plasma
20%
29
what % of the ECF is interstitial fluid
80%
30
how are body fluid compartments measured clinically
tracers of known volume
31
how is TBW measured
3H20
32
how is ECF measured
inulin
33
how is plasma measured
labelled albumin
34
what is the equation for volume of distribution
V(litres) = Dose (D) / Sample concentration (C)
35
what is total fluid input/output per day in normal temperature
2500ml/day
36
what happens to fluid input/output in hot weather
increases to around 3400
37
what happens to fluid input/output in prolonged heavy exercise
increases to around 6700
38
what are the main ions in the ECF
Na, Cl and HCO3
39
what are the main ions in the ICF
K, Mg and negatively charged proteins
40
Na is in higher concentration in ECF or ICF
ECF
41
K is in higher concentration in ECF or ICF
ICF
42
Cl- is in higher concentration in ECF or ICF
ECF
43
HCO3 is in higher concentration in ECF or ICF
ECF
44
what separates the ECF and ICF
selectively permeable plasma membrane
45
are the osmotic concentrations of the ICF and ECF the same or different?
identical
46
what is the osmotic concentration of ECF / ICF
300 mosmol/L
47
what is fluid shift
movement of water between the ICF and ECF in response to an osmotic gradient
48
what effect will ECF NaCl gain have on the ECF and ICF
change in fluid osmolarity
- increase in ECF
- decrease in ICF (Na excluded from ICF)
49
what effect will ECF NaCl loss have on the ECF and ICF
change in fluid osmolarity
- ECF loss
- ICF gain
50
what effect will gain or loss of water have on the ECF and ICF
change in fluid osmolarity
| - they will both increase or decrease
51
what effect will the gain or loss of an isotonic fluid e.g. 0.9% NaCl have on the ECF and ICF
no change in fluid osmolarity - only the ECF volume changes
52
what is an electrolyte
any salt that will dissociate to give ions in a solution
53
why are Na and K 2 of the most important electrolytes
major contributors to osmotic concentrations of ECF and ICF
| directly affect functioning of cells
54
why do minor fluctuations in plasma K ion concentrations have detrimental consequences
K plays a key role in establishing membrane potential
55
what are some consequences of changes in plasma K ion concentration
muscle weakness/paralysis
| cardiac arrhythmias/arrest
56
where is renin released from
granular cells (juxtaglomerular cells) within the juxtaglomerular apparatus
57
what is erythropoietin
hormone released by kidney in response to hypoxia
58
what is the name of active vitamin D
calcitrol
59
what role does calcitrol (active vitamin D) play in calcium absorption
promotes Ca2+ absorption from GI tract
60
how is vitamin D converted to its active form
addition of 2 hydroxy groups (OH)
61
where is the 1st hydroxy group added to vitamin D
liver
62
where is the 2nd hydroxy group added to vitamin D
kidney
63
what is the functional unit of a kidney
nephron
64
what are the 2 types of nephron
juxtamedullary
| cortical
65
what is the more common type of nephron
cortical (80%)
66
compare the loop of henle in juxtamedullary nephrons and cortical nephrons
juxtamedullary nephrons - much longer loop of henle that extends into the medulla
cortical nephron - loop of henle is much shorter and only slightly extends into the medulla
67
do juxtamedullary nephrons have peritubular capillaries
no - have a single capillary called a vasa recta
68
which type of nephron can produce much more concentrated urine
juxtamedullary nephrons
69
do cortical nephrons have a vasa recta
no they have a peritubular network of capillaries
70
does the efferent or afferent arteriole have a greater diameter
afferent arteriole has a greater diameter
71
what makes up the inner wall of the bowmanns capsule
specialised cells called podocytes
72
how is a filtration system created by the podocytes
they have foot like projections that interdigitate with the cells adjacent to them
73
true/false
| glomerular capillaries have pores in them which are much smaller than capillaries elsewhere in the body
false
| glomerular capillaries have pores in them that are 100 times bigger than capillaries elsewhere in the body
74
what % of plasma of afferent arteriole is filtered into bowmans capsule
20%
75
what are the macula densa cells
salt sensitive cells that sense how much salt is in the tubular fluid as it passes along - they can secrete vasoactive chemicals which can influence the smooth muscle in arterioles
76
what is urine
modified filtrate of the blood
77
what are the 3 renal processes
glomerular filtration
tubular reabsorption
tubular secretion
78
what is the equation for rate of excretion for any substance
rate of excretion = rate of filtration + rate of secretion - rate of reabsorption
79
what is the rate of filtration of X
the mass of X filtered into the bowmans capsule per unit time
80
what is the equation for rate of filtration of X
[X]plasma x GFR
81
what will happen to the rate of filtration of X if the concentration of X in the plasma increases
rate of filtration of X will increase
82
what is the rate of excretion of X
mass of X excreted per unit time
83
what is the equation for the rate of excretion of X
[X]urine x Vu
Vu is the rate of urine production
84
if the rate of filtration > rate of excretion, net _____ has occured
if the rate of filtration > rate of excretion, net reabsorption has occured
85
what is the equation for the rate of reabsorption of X
rate of filtration of X - rate of excretion of X
86
if the rate of filtration < rate of excretion, net ____ has occured
if the rate of filtration < rate of excretion, net secretion has occured
87
what is the equation for the rate of secretion of X
rate of secretion of X = rate of excretion of X - rate of filtration of X
88
what is the normal urine flow rate
Vu = 0.001 litre/min - very variable depending on body conditions
89
what 3 layers make up the glomerular filtration barrier
glomerular capillary endothelium
basement membrane
slit processes of podocytes
90
what is the net charge of the basement membrane and why is this
negative
| to repel large negatively charged proteins
91
what are the 2 forces pushing out from the blood vessels into the filtrate
glomerular capillary pressure
| bowmans capsule oncotic pressure
92
what is the glomerular capillary pressure roughly
55mmHg
93
what is the bowmans capsule oncotic pressure
0mmHg
94
why is the bowmans capsule oncotic pressure 0
no plasma proteins
95
what determines oncotic pressure
plasma proteins
96
what are the 2 forces pushing back and resisting the movement from the blood vessels into the filtrate
bowmans capsule hydrostatic pressure
| capillary oncotic pressure
97
what is bowmans capsule hydrostatic pressure
15mmHg
98
what is the capillary oncotic pressure
30mmHg
99
what is the net filtration pressure equation
(BPgc + COPbc) - (HPbc + COPgc)
100
what contributes most to net filtration pressure at the glomerulus
BPgc (glomerular capillary blood pressure)
101
what are the forces that balance hydrostatic pressure and osmotic forces known as
staring forces
102
what is the GFR
the glomerular filtration rate at which protein-free plasma is filtered from the glomeruli into the Bowman's capsule per unit time
103
what is the equation for GFR
Kf x net filtration pressure
104
what is Kf
filtration coefficient - how holey the glomerular membrane is
105
what is GFR normally
125ml/min
| 0.125L/min
106
what is the major determinant of GFR
glomerular capillary fluid pressure
107
how is GFR regulated extrinsically
sympathetic control via the baroreceptor reflex
108
how is the GFR regulated intrinsically (autoregulation)
myogenic mechanism
| tubuloglomerular feedback mechanism
109
an increase in arterial blood pressure ____ the blood flow into the glomerulus. This in turn _____ the glomerular capillary blood pressure and net filtration pressure therefore _____ the GFR
increases
increases
increases
110
how is the blood pressure between afferent and efferent arteriole kept constant
as you lose volume the diameter decreases
111
afferent arteriole (vasoconstriction/vasodilation) will increase the GFR
afferent arteriole vasodilation will increase the GFR because blood flow into the glomerulus is increased
112
afferent arteriole (vasoconstriction/vasodilation) will decrease the GFR
afferent arteriole vasoconstriction will decrease the GFR because blood flow into the glomerulus is decreased
113
a fall in blood volume does what to arterial blood pressure
decreases
114
what detects changes in arterial blood pressure
aortic and carotid sinus baroreceptors
115
if baroreceptors detect a fall in ABP what do they do
reduced firing of baroreceptors causing increase in sympathetic activity
116
what effect does increased sympathetic activity have on the arterioles
generalised arteriolar vasoconstriction
| constriction of afferent arterioles
117
what does constriction of afferent arterioles due to sympathetic stimulation do to the GFR
decreased blood pressure in the glomerular capillaries (BPgc) so GFR is reduced - less urine produced to help compensate fall in blood volume
118
does systemic arterial BP change always result in change in GFR
no - autoregulation prevents short term changes in systemic arterial BP affecting GFR
119
GFR remains constant despite a large increase in MAP
| true or false
true
120
in situations such as haemorrhage, does intrinsic or extrinsic control of GFR take over
extrinsic
121
what does autoregulation of GFR mean
intrinsic to kidneys - needs no external input
122
describe the intrinsic myogenic control
if vascular smooth muscle is stretched (arterial pressure is increased) it contracts thus constricting the arteriole
123
what does the tubuloglomerular feedback involve
juxtaglomerular apparatus - if NaCl increases within the distal tubular fluid i.e. GFR has increased, the macula densa senses this and release vasoactive chemicals which causes contraction of smooth muscle in the walls of the afferent arterioles to reduce GFR
124
what kind of feedback do the macula densa cells exert on GFR
negative feedback
125
what effect does a kidney stone have on the GFR and why
decreases GFR
| - blockage downstream so bowmans capsule fluid pressure increases
126
what effect does diarrhoea have on the GFR and why
GFR decreases
- patient will be dehydrated so plasma proteins within the blood are more concentrated and exert a greater osmotic force (capillary oncotic pressure increases)
127
what effect do severe burns have on the GFR and why
increase the GFR
-plasma proteins are lost so conc. within the blood decreases exerting a weaker osmotic effect (capillary oncotic pressure decreases)
128
what is plasma clearance
volume of plasma completely cleared of a particular substance per minute (ml/min)
129
what is the equation for clearance of a substance
clearance of a substance = rate of excretion/plasma conc
| = (( [X]urine x Vurine )) / [X]plasma
130
what is the plasma clearance of inulin equal to
GFR
131
why is the plasma clearance of inulin equal to GFR
it is freely filtered at the glomerulus
132
is inulin reabsorbed
no
133
is inulin secreted
no
134
is inulin metabolised by the kidney
no
135
is inulin toxic
no
136
can inulin be easily measured in the urine
yes
137
what is the inulin clearance rate in a person with normal GFR
125ml/min
138
true/false
| amount of inulin filtered per unit time = amount of inulin excreted per unit time
true
139
what is another chemical that can be used instead of inulin to measure GFR
creatinine
140
what is a benefit to using creatinine
occurs naturally so doesnt have to be given to the patient
141
what is a disadvantage to using creatinine
some creatinine is secreted in the tubules
142
what is the plasma clearance of glucose
0
143
why is the plasma clearance of glucose 0
completely reabsorbed in the proximal tubule
144
clearance of a substance will be 0 if... (2 scenarios)
filtered, entirely reabsorbed and not secreted
or
not filtered and not secreted
145
give an example of a substance that will have a plasma clearance rate of < GFR
urea
146
why is the clearance of urea less than the GFR
urea is filtered, partly reabsorbed and not secreted
| i.e. only a portion of the plasma is cleared of the substance
147
give an example of a substance that has a clearance > GFR
H+
148
why is the clearance of H+ > than GFR
H+ is filtered, secreted but not reabsorbed
| i.e. all of the filtered plasma is cleared of the substance, as is the peritubular fluid from which it is secreted
149
true/false
| more H+ is excreted that was initially filtered because it is drawn out of the blood vessels and not reabsorbed
true
150
if clearance is < GFR the substance is ...
reabsorbed
151
if clearance = GFR the substance is...
neither reabsorbed not secreted
152
if clearance > GFR the substance is ...
secreted
153
how is renal plasma flow calculated
clearance of PAH (para-amino huppuric acid)
154
```
PAH is
freely filtered/not filtered
secreted/not secreted
reabsorbed/not reabsorped
completely cleared/not completely cleared
```
freely filtered
secreted
not reabsorbed
completely cleared
155
does the blood leaving the kidneys contain any PAH
no
156
what is creatinine a breakdown product of
muscle
157
what is the clearance value of PAH
650ml/min = RPF
158
what is used to estimate GFR
creatinine
159
```
creatinine is :
produced at a constant/near constant rate
freely filtered/not filtered
reabsorbed/not reabsorbed
secreted/not secreted
```
near constant rate
freely filtered
not reabsorbed
slightly secreted
160
a GFR marker should be ...
freely filtered
not secreted
not reabsorbed
161
an RPF marker should be
freely filtered
completely secreted
not reabsorbed
162
what is the equation for filtration fraction
GFR/RPF
163
What is the filtration fraction value
125/650 = 0.19 = 20%
164
what does the filtration fraction tell us
20% of the plasma entering the glomeruli is filtered - remaining 80% moves onto the peritubular capillaries
165
how many litres a day does a GFR of 125ml/min equate to
180 litres per day
166
what is the equation for RBF
RPF x 1/ 1-Hct
167
what does renal blood flow roughly equate to
1200 ml/min
168
what is the CO in litres/min
5 litres
169
what % of the CO do the kidneys receive
around 24%
170
what % of fluid is reabsorbed by the kidneys
99%
171
what % of salt is reabsorbed by the kidneys
99%
172
what % of glucose is reabsorbed by the kidneys
100%
173
what % of amino acids are reabsorbed by the kidneys
100%
174
what % of urea is reabsorbed by the kidneys
50%
175
what % of creatinine is reabsorbed by the kidneys
0%
176
is reabsorption or filtration more specific
reabsorption
177
of the 125ml of glomerular filtrate, how many ml is reabsorbed in the PCT and therefore how much is left to go into the loop of henle
80ml is reabsorbed in the PCT
| 45ml goes on to the loop of henle
178
true/false
| the fluid filtered changes osmolarity from the bowmans capsule to the proximal tubule
false - doesnt change osmolarity from the bowmans capsule to the PCT
179
fluid reabsorbed in the PCT is hyperosmotic/isoosmotic/hypoosmotic with the filtrate
isoosmotic
180
give 5 things reabsorbed in the PCT
```
sugars
amino acids
phosphate
sulfate
lactate
```
181
give 6 things secreted in the PCT
```
H+
hippurates
neurotransmitters
bile pigments
uric acid
drugs
toxins
```
182
what are the 2 pathways used in reabsorption
transcellular and paracellular
183
describe the transcellular pathway
absorption across the cell of the tubular wall
184
describe the paracellular pathway
absorption across spaces in the cells of the tubular wall
185
what are the names of the junctions between tubular epithelial cells
tight junctions
186
what are the 2 membranes of the tubular epithelial cells and which borders the tubular lumen and which borders the interstitial fluid
luminal membrane - in contact with filtrate
| basolateral membrane - in contact with interstitial fluid
187
what is primary active transport
energy is directly required to operate the carrier and move the substrate against its concentration gradient
188
what is secondary active transport
carrier molecule is transported coupled to the concentration gradient of an ion (usually Na+)
189
what is facilitated diffusion
passive carrier-mediated transport of a substance down its concentration gradient
190
what is facilitated diffusion usually used for
substances that do not easily move across the lipid bilayer
191
where is the Na+/K+/ATPase transport mechanism expressed ALWAYS AND EXCLUSIVELY
basolateral membrane of epithelial cells
192
what does the Na+/K+/ATPase channel pump out of the cell
3 sodium
193
what does the Na+/K+/ATPase channel pump into the cell
2 potassium
194
why does the Na+/K+/ATPase channel require energy from hydrolysis of ATP
pumping sodium and potassium against their concentration gradients
195
the intracellular concentration of Na is kept low by the Na+/K+/ATPase allowing Na to -------- from the tubular lumen into the cell ----- a concentration gradient
the intracellular concentration of Na is kept low by the Na+/K+/ATPase pump allowing Na to diffuse from the tubular lumen into the cell down a concentration gradient
196
how does fluid reabsorption occur across the leaky PCT epithelium
standing osmotic gradient
| oncotic pressure gradient
197
in what direct do the mechanisms on the apical membrane of the PCT move Na
into the cell
198
in what direction do the mechanisms on the basolateral membrane of the PCT move Na
out of the cell into the interstitial fluid
199
what are the 3 mechanisms at the apical border that bring Na into the cell
Na+/glucose
Na+/amino acids
Na+/H+
200
what kind of transport are the Na+/glucose and Na+/amino acid mechanisms
secondary active transport
201
what kind of transport is the Na+/H+ mechanism
countertransport
202
how is Cl- reabsorbed from the filtrate
paracellular route along an electrochemical gradient set up by the reabsorption of sodium ions
203
how does water get reabsorbed in the PCT
paracellular mechanism due to the osmotic gradient created by Na and Cl (osmosis)
204
how does glucose cross the apical membrane of the tubular cell from the filtrate into the cell
Na+/glucose
| cotransport/symport/secondary active transport
205
how does glucose cross the basolateral membrane of the tubular cell
facilitated diffusion
206
the Na+/K+/ATPase channel is an example of what kind of transport
primary active transport
207
what % of glucose in the filtrate is reabsorbed in the PCT
100%
208
why is there glucose in the urine of people with diabetes
transport maximum exists as transporters can only move so many molecules in a given time - if there is too much glucose present in the filtrate they become saturated - no more glucose can be reabsorbed
209
what is the Tm of glucose
approx 2mmol/min
210
how much of salt and water is reabsorbed in the PCT
2/3
211
what % of amino acids are absorbed in the PCT
100%
212
what drives the Na reabsorption in the PCT
basolateral Na+/K+/ATPase channels
213
the tubular fluid is hyperosmotic/isoosmotic/hypoosmotic when it leaves the PCT
isoosmotic - same osmolarity as plasma (around 300mosmol/l)
214
why is the tubular fluid isoosmotic when it leaves the PCT
salt and water have been reabsorbed in correlating amounts
215
why does the vasa recta have a higher oncotic pressure than the afferent arteriole
same number of plasma proteins but 20% of plasma has gone so increased concentration of plasma protein
216
what is the function of the loop of henle
generates a corticomedullary solute concentration gradient enabling the formation of hypertonic urine
217
where does the loop of henle originate
junction between the cortex and medulla
218
where is the concentration gradient found that is created by the loop of henle
interstitial fluid
219
what is the term for the opposing flow in the 2 limbs of the loop of henle
countercurrent flow
220
the entire loop functions as a _____ _____ _____
counter current multiplier
221
together the loop and the vasa recta establish a hyper/iso/hypo osmotic medullary interstitial fluid
hyperosmotic medullary interstitial fluid
222
what happens to Na and Cl along the entire length of the ascending limb
Na and Cl are reabsorbed
223
how is Na and Cl reabsorption achieved in the upper thick ascending limb
active transport
224
how is Na and Cl reabsorption achieved in the lower thin ascending limb
passive movement
225
is water reabsorbed in the ascending limb
no - ascending limb is relatively impermeable to water so little/no water is follows salt
226
is NaCl reabsorbed in the descending limb
no
227
is water reabsorbed in the descending limb
yes - highly permeable to water
228
why does water move out of the descending limb
follows the osmotic gradient created by the interstitial fluid - originally created by reabsorption of NaCl from ascending limb
229
what pumps ions out of the thick ascending loop of henle
Na+/K+/Cl- triple cotransporter
230
what drugs block the Na+/K+/Cl- triple cotransporter
loop diuretics
231
the Na+/K+/Cl- triple cotransporter causes the tubular fluid to become ____ and the osmolality of the interstitial fluid to ____
dilute
| increase
232
can interstitial fluid enter the descending limb
no - impermeable to ions
233
water leaves the descending limb by ____ causing the fluid in the descending limb to be _____
osmosis
| concentrated
234
on the way down the descending limb there is _____ in osmolality due to _____
increase
| reabsorption of water
235
on the way back up the ascending limb there is _____ in osmolality due to ____
decrease
| active salt reabsorption
236
horizontal gradient is much larger/smaller than the vertical gradient in the loop of henle
smaller
237
tubular fluid is hyper/iso/hypo osmotic when it leaves the loop of henle to enter the DCT
hypoosmotic
238
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 forming the corticomedullary gradient
239
approximately how much of the medullary osmolarity is contributed by the urea cycle
1/2
240
what is the two salt hypothesis
corticomedullary concentration is set up by salt movement but also by other substances such as urea
241
the purpose of countercurrent multiplication is to enable the kidney to produce a urine of different volume and concentration according to the amounts of circulating ___
ADH
242
urine production is usually around 1ml/min but what can it vary between
0.3 - 25 ml /min
243
what runs along side the loop of henle of juxtamedullary nephrons acting as a countercurrent exchanger
vasa recta
244
what happens to the osmolality of the blood in the vasa recta as it dips into the medulla
osmolality rises as it dips down into the medulla - water is lost and solute is gained
245
what happens to the osmolality of the blood as it goes back up to the cortex
osmolality falls as blood goes back up to the cortex as water is gained and solute is lost
246
the blood is said to ------ with the corticomedullary gradient
equilibrate
247
what two things form the counter current system
the loop of henle (countercurrent multiplier) and the vasa recta (countercurrent exchanger)
248
how is the medullary gradient preserved
passive exchange across endothelium - blood equilibrates at each layer - ensures the solute is not washed away
249
how does the vasa recta minimise the washing away of NaCl and urea by essential blood flow through the medulla (3)
vasa recta capillaries follow hairpin loops
vasa recta capillaries are freely permeable to NaCl and water
blood flow to the vasa recta is low - only a few juxtamedullary nephrons
250
blood entering and leaving the vasa recta is of different/the same osmolarity
the same (300mosmol/L)
251
the tubular fluid leaving the loop of henle entering the distal tubule is hyper/iso/hypertonic to plasma
hypotonic (100mosmol/L)
252
tissue surrounding the distal tubule (renal cortext interstitial fluid) is at around ___mosmol/L
300
253
where do the distal tubules empty
cortical collecting ducts
254
the collecting duct is bathing in progressively increasing/decreasing concentration of surrounding interstitial fluid as it decends through the medulla
increasing
255
when the distal tubules reach the collecting ducts, what % of filtered ions have been reabsorbed
95%
256
ADH causes water ____
reabsorption
257
Aldosterone _____ Na reabsorption and _____ H+/K+ secretion
aldosterone increases Na reabsorption
| aldosterone increases H+/K+ secretion
258
Atrial natriuretic hormone ____ Na+ reabsorption
decreases
259
Parathyroid hormone ____ Ca2+ reabsorption and ____ phosphate reabsorption
increases Ca2+ reabsorption
| decreases phosphate reabsorption
260
the distal tubule has a ____ permeability to water and urea, meaning urea is _____ in the tubular fluid
low
| concentrated
261
the distal tubule can be split into 2 sections:
early and late
262
what occurs in the early tubule and via what transporter
NaCl reabsorption
| Na+/K+/2Cl- transport
263
what occurs in the late tubule
Ca reabsorption
| H+ secretion, Na+, K+ reabsorption
264
the collecting duct is also split into 2 sections:
early and late
265
the early collecting duct is similar to the ____ distal tubule
late
266
the late collecting duct has ____ ion permeability
low
267
what influences the permeability of the late collecting duct to water and urea
ADH
268
where is ADH synthesised
supraoptic and paraventricular nuclei in the hypothalamus
269
where is ADH stored
granules in the posterior pituitary
270
how is ADH transported from the hypothalamus to vesicles in the posterior pituitary
transported down nerves
271
how is ADH released into blood
when APs down the nerves lead to Ca2+ dependent exocytosis
272
dehydration leads to an ____ in plasma osmolarity which _____ the release of ADH
increase
| stimulated
273
what kind of hormone is ADH
peptide
274
what is the half life of ADH
10-15 minutes
275
ADH will bind to Type _ vasopressin receptors on the ______ membrane
type 2 vasopressin receptors on the basolateral membrane
276
what does the binding of ADH to V2 receptors cause
increase in amount of intracellular cAMP which increases expression of aquaporins on the apical membrane
277
where are aquaporins usually found
within vesicles in the cytoplasm of the cell
278
where do aquaporins move when stimulated
to the apical membrane where they are inserted
279
when there is no more ADH stimulation where do aquaporins go
back into the cytoplasm
280
low plasma ADH produces ____ urine
hypotonic
281
high plasma ADH produces _____ urine
hypertonic
282
high levels of ADH ____ the permeability of the collecting duct cells to water
increase
283
what do type 1 vasopressin receptors cause
smooth muscle contractions and vasoconstriction
284
tubular fluid _____ with interstitium via ____
equilibrates via aquaporins
285
when dehydrated, there is an _____ in plasma concentration causing more/less ADH to be released. Osmolarity of the tubular fluid will ____ because
when dehydrated there is an increase in plasma concentration causing more ADH to be released. Osmolarity of the tubular fluid will increase because water starts to move out as it passes down the osmotic gradient of the kidney (set up by the loop of henle)
286
a dehydrated person will produce a _____ volume of ___ urine
small volume of concentrated
287
with low levels of ADH, the collecting ducts are ______ to water
relatively impermeable to water
288
why does water not move out of the collecting ducts when there is low levels of ADH despite the osmotic gradient it is exposed to
low ADH so less aquaporins are expressed so no pathway for water to take - high volume of dilute urine
289
what are the 2 types of diabetes insipidus
central and nephrogenic
290
what is the issue in central DI
person cannot secrete ADH
291
what is the issue in nephrogenic DI
ADH is produced but isnt influencing or causing a response in the cells of the collecting duct
292
true/false
| DI is usually hereditary
true
293
what are the main s/s of DI
large volumes of dilute urine (20L per day)
| constant thirst
294
what is the treatment for central DI
ADH replacement
295
what is the treatment for nephrogenic DI
thiazide diuretics
296
what are the 2 types of receptor which stimulate ADH release and which is more important
hypothalamic osmoreceptors - most important
| left atrial stretch receptors
297
what does decreased left atrial pressure lead to
increased ADH release
298
what does nicotine do to ADH release
stimulates
299
what does alcohol do to ADH release
inhibits
300
what does ecstasy do to ADH release
inhibits
301
stimulation of stretch receptors in upper GI tract exerts feed-_____ ______ of ADH
feed forward inhibition
302
what kind of hormone is aldosterone
steroid
303
where is aldosterone secreted from
adrenal cortex
304
aldosterone is secreted in response to _____ K+ concentration or _____ Na+ concentration and in activation of the _____ system
increasing K+
decreasing Na+
RAAS
305
aldosterone stimulates the ____ of Na and ____ of K+
reabsorption of Na
| secretion of K
306
around ___% of K is reabsorbed in the PCT.
| when aldosterone is absent the remainder is ____
90%
| reabsorbed in the distal tubule
307
an increase in plasma K+ concentration (directly/indirectly) stimulates the adrenal cortex to release aldosterone causing the ____ of K
directly
| secretion
308
a decrease in plasma Na+ concentration (directly/indirectly) promotes the secretion of aldosterone
indirectly by means of the juxtaglomerular apparatus
309
what causes release of renin from the kidney
increased sympathetic activity due to reduced BP
reduced NaCl
reduced pressure in the afferent arteriole
310
where is renin released from
granular cells in the JGA
311
granular cells are directly innervated by the ______ nervous system - causes renin release
sympathetic
312
where does aldosterone increase Na+ reabsorption
distal tubule and collecting duct
313
what channels does aldosterone increase the expression of
K/Na pumps on the basolateral membrane
| Na channels on apical membrane
314
renin converts what to what
angiotensinogen to angiotensin I
315
what converts angiotensin I to angiotensin II
ACE
316
angiotensin II stimulates the adrenal cortex to produce ____
aldosterone
317
angiotensin II causes arterior _____
vasoconstriction
318
angiotensin II causes ___ thirst
increased
319
where is ANP produced
heart
320
where is ANP stored
atrial muscle cells
321
when is ANP released
when atrial muscle cells are mechanically stretched due to an increase in the circulating plasma volume
322
ANP promotes ____ of Na+ therefore ____ plasma volume
excretion
| decreasing
323
ANP has the ____ effects on the kidney to aldosterone
opposite
324
ANP ____ RAAS
inhibits
325
ANP causes smooth muscle of afferent arteriole to ____
relax/dilate
326
ANP _____ the sympathetic nervous system to _____ TPR and CO
inhibits
| decrease
327
what 2 mechanisms control micturation
micturation reflex
| voluntary control
328
what stimulates the micturation reflex
stretch receptors in the bladder wall
329
what is the micturation reflex
involuntary emptying of the bladder by simultaneous bladder contraction and opening of both the internal and external urethral sphincters
330
how can micturation be prevented
voluntarily prevented by deliberate tightening of the external sphincter and surrounding pelvic diaphragm
331
what is water diuresis
increased urine flow but not an increased solute excretion
332
what is osmotic diuresis
increased urine flow as a result of primary increase in salt excretion
333
true/false
| any loss of solute in the urine must be accompanied by water
true
334
true/false
| any loss of water in the urine must be accompanied by solute loss
false
| water loss can occur without the loss of solute
335
the collecting duct absorbs around __% of urea
50%
336
is the distal tubule permeable to urea
no
337
parasympathetic/sympathetic nervous system causes the bladder to contract
parasympathetic
338
stretch receptors ____ motor neurone to the external sphincter
inhibit
339
voluntary control: cerebral cortex ____ motor neurone to the external sphincter
stimulates
340
when motor neurone to external urethral sphincter is stimulated, the external urethral sphincter ____
remains closed
341
what receptors detect and initiate the primary mechanism for regulation of ECF osmolarity
hypothalamic osmoreceptors
342
renal mechanisms suffice in water excess or deficit?
excess
| in deficit it is essential to increase intake
343
kidneys produce erythropoietin which stimulates
stem cells in bone marrow to produce RBCs to increase O2 supply in tissues
344
when do kidneys produce more erythropoietin
if O2 supply in tissues is too low
