GI Theme 3 Flashcards
(283 cards)
1
Q
What is the structure of amylose ?
A
linear polymer of alpha 1-4 glycosidic links
2
Q
What is the structure of amylopectin ?
A
branched polymer with alpha 1-4 and alpha 1-6 glycosidic links
3
Q
Where can you find alpha amylase ?
A
pancreatic juice and saliva
4
Q
What does amylase hydrolyse and what cant it ?
A
hydrolyses alpha 1-4 links
cant hydrolyse alpha 1-6 links or alpha 1-4 linkks close to terminal branches ?
5
Q
Starch digestion release what
A
maltose
maltotriose
alpha limit dextrins
6
Q
What are alpha limit dextrins?
A
branched polymers of glucose 5-9 units long
formed due to the inability of amylase to hydrolyse alpha 1-4 links next to branch points
7
Q
What happens to alpha limit dextrins in the mouth ?
A
they can be taken up by bacteria and used as an energy source
8
Q
The length of time food is in the mouth detemrines what ?
A
how much maltose and maltotriose is released
they are carcinogenic
9
Q
What carbohydrate digestion takes place in the stomach ?
A
none- acidic pH inhibits alpha amylase
10
Q
What carbohydrate digestion takes place in the duodenum ?
A
pancreatic alpha mylase
digests remaining starch into maltose , maltotriose and alpha limit dextrins
11
Q
Which is faster salivary alpha amylase or pancreatic alpha amylase ?
A
pancreatic alpha amylase
12
Q
What is the role of oligosaccharidases ?
A
on the brush border
they further digest the maltose, maltotriose and the alpha limit dextrins
13
Q
Where can you find oligosaccharidases ?
A
in the duodenum and the jejunum
14
Q
What does isomalatase (alpha dextrinase) do ?
A
hydrolyse alpha 1-6 links that amylase csnt
15
Q
What does maltase do ?
A
hydrolyse maltose and maltotriose into glucose
16
Q
What does lactase do ?
A
hydrolyse lactose into glucose and galactose
17
Q
What does sucrase do ?
A
hydrolyse sucrose into glucose and fructose
18
Q
What are the end products of digestion with oligosaccharidases ?
A
monosaccahrides- glucose , fructose and galactose which can be absorbed by the duodenum and jejunum
19
Q
Where does the absorption of monosaccahrides occur ?
A
duodenum and upper jejunum
20
Q
How are glucose and galactose actively uptaken ?
A
by sodium-glucose transporter 1
21
Q
What type of active transport does the sodium-glucose transporter use ?
A
secondary active transport
22
Q
What creates the electrochemical gradient in sodium-glucose active transport ?
A
Na/K ATPase
basolateral membrane
23
Q
How do glucose and galactose leave the epithelial cell ?
A
glucose transporter protein 2
24
Q
How is the entry of galactose and glucose into the epithelial cell mediated ?
A
by the presence of sodium in the GI lumen
25
How does fructose enter and leave the intestinal epithelial cell ?
enters using facilitated diffusion - glucose transporter 5
| exits using glucose transporter 2
26
What is sucrase-isolmaltase deficiency ?
low levels of sucrase and isomaltase in the brush border
intolereane to starch and sucrose
fructose and glucose are tolerated
27
What is glucose-galactose malabosprtion syndrome ?
mutation in SGLT-1
| fructose can be given
28
What type of transport is SGLT?
secondary active trnasport
| symport
29
What is the type of transport with GLUT proteins ?
facilitated diffusion
| uniport
30
What are alpha limit dextrins hydrolysed by ?
isomaltase
31
How is pepsinogen converted to pepsin ?
by protons
32
How much protein does pepsin digest ?
15%
33
What is pro elastase ?
converted to elastase
| digests serine in elastin
34
What are the peptidases ?
aminopeptidase
dipeptidase
dipetidyl aminopeptidase- cleaves a dipeptide from end of the dipeptide
35
How can small peptides be further hydrolysed ?
by peptidases in the cytosol
36
What is present on the apical membrane to provide gradients for peptide transport ?
Na/H transporters
37
What are the amino acid transport systems on the apical membrane ?
5 dependent on Na - active
2 are facilitated
7 in total
38
What are the amino acid transport systems on the basolateral membrane ?
5
3 are Na independent - efflux of amino acids into blood
2 are Na dependent - active
39
How do fat soluble vitamins diffuse ?
diffuse acorss the brush border membrane
40
Where is vit B12 absorbed ?
ileum
41
How is B12 found in foods ?
bound to proteins
42
What happens to b12 in the stomach ?
released and binds to R proteins - high affinity
43
What is intrinsic factor ?
vitamin b12 binding protein
secreted by gastric parietal cells
binds to B12 with less affinity than R proteins
44
What degrades the R - protein B12 complexes ?
pacnreatic proteases
45
What happens to the B12 afte degradation from R proteins ?
binds to IF- resist protease degradation
46
What happens to the B12 afte degradation from R proteins ?
binds to IF- resist protease degradation
47
What does the brush border of the ileum contain ?
receptors for B12- IF complexes
48
What might happen in pancreatic insuffficinecy ?
no degradation from R proteins
| B12 deficiency might occur
49
What is the B12 carrier ?
transcobalamine II
50
What inhibits gastric emptying locally ?
CCK - lipid present in the duodenum
51
What emulsifies lipids ?
bile salts and lecithin
52
What is the purpose of emulsification ?
increase the surface area for water soluble enzymes to act
53
What are the lipolytic enzymes found in pancreatic juice ?
pancreatic lipase
co-lipase
cholesterol esterase
phospholipase A
54
How is pancreatic lipase inhibited ?
bile salts bind to fat surface and prevent lipase binding
55
What does co lipase do ?
displaces bile salts on the fat surface enabling lipase to fucntion
56
What are the products of triglyceride break down ?
2-monoglyceride
| 2 x NEFA
57
What does cholesterol esterase do ?
cleaves a fatty acid from cholesterol esters
58
What does phospholipase A2 do ?
turns phsopholipids into lypophospholipid and NEFA
59
What is micelle formation ?
bile salts form micelles with the products of fat digestion
60
What do the bile salts act as in micell formation ?
surfactant
61
What is the structure of micelles ?
lipid molecules arranged in a spherical form
62
Where does absorption of lipids take place ?
in the ileum and the jejunum
63
What is the unstrirred layer ?
mucus layer
with microvilli between the lumen and the brush border
molecules pass through and become more disorgansied as they approach the apical membrane
64
What lipid transport occurs at the brush border membrane ?
cholesterol transporter mediates facilitated transport
microvilli membrane fatty acid binding protein transports long chain fatty acids by secondary active transport - Na/K ATPase
65
What is the role of cytosolic transport membrane ?
transport the products of lipid digestion to the smooth endoplasmic reticulum
66
What are the cytosolic lipid transport proteins ?
fatty acid binding protein and sterol carrier
67
What happens to lipids in the smooth endoplasmic reticulum ?
they are esterified again
enter pre chylomicrons
go to golgi
too large to leave across the basement membrane
lacteals - lymphatic capillaries- large enough - empty into the lymph and the the blood by the thoracic duct
68
Where does absorption of bile salts occur ?
in the terminal ileum
69
How are conjugated bile salts actively taken up ?
by an Na bile duct co transporter
70
How do bile salts enter the blood ?
they re enter the portal blood
bound to albumin
return to the liver
71
How does fructose get from the gut to the blood ?
enters via facilitated diffusion and then leaves bu GLUT 5
72
What are the brush border peptidases ?
aminopeptidase
dipeptidase
dipeptidyl aminopeptidase
73
Where does lipid break down occur in the GI tract ?
stomach
duodenum
jejunum
74
What 2 substances are responsible for emulsification ?
bile salts and lecithin
75
What is the role of R protein ?
to protect IF from gastric acid
76
Which compounds predominantly contribute to micelle formation ?
bile salts
77
What is the mechanism whereby lipids in the duodenum prevent gastric emptying ?
CCK
78
what are anciliary organs of digestion
pancreas, gallbladder and liver
79
how long is the human gut
5m long
80
how is the sa increased in the human gut
folds and microvilli in the SI
81
outline the journey through the gut
```
Oesophagus
Pyloric sphincter and stomach
Upper small intestine
Lower small intestine
Caecum
Colon
Rectum
```
82
what are the GI Tract Disorders
Physical (blockages/strictures/ fat deposition)
Functional (nerve-peristalsis/muscle)
Environmental insult (infections, toxins, DNA mutations)
Immune-related ( defence becomes attack)
Unknown aetiology
All may have metabolic implications
83
what disorder affect the whole length of the GI tract
GI cancers
| Crohns disease
84
what disorders move down the GI tract
oesophagus:
- Dysphagia (difficulty swallowing)
Oesophageal stricture/tumours
Oesophageal varices (liver disease)
Oesophageal reflux/indigestion
Barret’s oesophagus
85
what is dysphagia
oropharygeal
- neuromuscular disorders or stroke
- cant close trachea
- choking
- aspiration pneumonia
- anxiety, anorexia
- dehydration
86
how can dysphagia be managed
soft diet
pureed diet
thickened fluids
PEG- feeding tube, long term feeding
87
what happens in dysphagia
food can go to lungs
88
what is oesophageal stricture
```
food sticking after swallowing
caused by
- achalasia
-astrictures
-present with dysphagia
```
89
how can oesophageal stricture be treated
dietery management
| surgical
90
what is Gastroesophogeal Reflux Disease (GORD)
Reflux of gastric contents through lower oesophageal sphincte
91
what is Chronic: GORD
potential progression to Barret’s Oesophagus/cancer
92
what can GORD be aggrevated by
Spicy and fatty foods, tomatoes, onion, garlic
Caffeine and alcohol, carbonate drinks
Obesity and pregnancy
93
what is Laryngo-pharyngeal Reflux (LPR)
refluxate that travels above the upper oesophageal sphincter
94
is LPR physiological
no
95
How is GORD linked to erosive tooth wear
Intrinsic acids from the stomach can travel to the mouth and can damage enamel and dentin
96
how is erosive tooth wear managed in those with GORD
dental treatment & PPI therapy
97
what is hiatus hernia
stomach protrudes up to chest cavity
98
what is dyspepsia
discomfort in upper abdomen thta is food related
99
what is the cause of dyspepsia
peptic ulcer (by bacterial infection- helicobacter pylori)
100
what is the treatment for peptic ulcers
single 14 dyacourse combinatin therapy leading to healing
101
why are 2 antibiotics needed to treat peptic ulcers
h pylori can be antibiotic resistant
102
what is perniciuos anaemia
automimmune destrcution of gastric parietal cells that produce IF
103
what happens to rbc in pernicious aneamia
large
104
what are the symptoms of pernicuous anaemia
```
extreme fatigue
shortness of breath
pins and needles
muscle weakness
mood swings
memory
```
105
how is pernicuous anaemia treated
vit b injection every 3 mnths
106
what are the oral symptoms of B12 deficiency
atrophic glossitis (sore and red beefy tongue)
mouth ulcers
angualr chleiltis
107
what is coeliac disease
autoimmune resposne to gluten and gliadin proteins
| - wheat, rye, barley. oats
108
what happens in coeliac disease
damage to villi which affects absorption of nutrients
109
what are the complication in coeliac disease
anaemia
osteoporosis
neurological conditions
increased risk of small bowel cancer and intestinal lymphoma
110
how is coelaic disease managed
complete avoidance of gluten
gluten free breads
iron calcium and folate supplement
111
what crohns disease
inflammatory disease
112
what causes crohns disease
genetics
inapropirate immune response to commensal bacteria
environmental trigger
113
where can crohns disease occur
any where in gi tract from mouth to anus
114
what are the symptoms of crohns disease
```
Abdominal pain
Diarrhoea
Nausea and vomiting
Fatigue
Weight loss
fistule- 2 parts of SI join
anal fissures
```
115
Crohn’s Disease Complications
```
Inflammation
Strictures/blockages
Abscesses
Fistulae- 2 parts of SI join
Anal fissures
Bacterial Overgrowth
Toxic megacolon
```
116
what are treatments for crohns disease
```
Steroids
Antibiotics
Liquid diet
Supplementary nutrition
Surgeries (multiple
```
117
what are the oral symptoms of crohns disease
mouth sores
ulcers
swellings
gum problems
118
what are the oral symptoms of crohns disease
mouth sores
ulcers
swellings
gum problems
119
what are the disorders moving down the gi tract (large intestine)
diverticular disease
| irritable bowel disease
120
what is diverticular disease
pockets created in teh lining trapping food and waste
121
what is diverticular disease caused by
thickening of msucle in colon casuing extra pressure
122
how is diverticular disease treated
fibre in diet
123
what is IBS
disorder of the motor activity whole bower but mostly colon
124
how can IBS be managed
low FODMAP
125
how is IBS diagnosed
when all other caused are ruled out
126
what is the microbiome
role of bacteria in periodontitis
| role in digestion, vit production, immune function
127
what does the gut microbiome have implications for
obesity
cancers
mental health
autism?
128
What are the functions of the kidney ?
Excretion
Homeostasis
Hormone production
129
What does the kidney excrete ?
foreign substances and products of metabolsim
urea
creatinine
hormones and drugs
130
What does the kidney regulate in homeostasis ?
```
ECF volume
blood pressure
osmolarity
ion levels- calcium and potassium
regulation of pH
```
131
What hormones does the kidney produce ?
renin
132
Urine produced by the kidney travels where ?
out of the kidney via the ureter and into the bladder where it is expelled by the urethra
133
Where does the renal vein drain back into ?
inferior vena cava
134
What are the 2 types of nephrons ?
cortical- Superficial cortical and the midcortical
| juxtamedullary- penetrate deeply into the medulla and surrounded by the vase recta
135
where is the loop of henle longer
in the juxtameduallry nephrons therefore th urine id more cocnentrated
136
What is the glomerulus ?
a cluster of blood vessels
| water and solutes flter from the blood into the renal tubule through the glomerulus
137
What is the glomerulus bounded by ?
the afferent and the efferent arterioles
138
What is the purpose of the afferrent and the efferent arterioles ?
they contain smooth muscle which contracts to increase blood pressure
139
What is the nephron surrounded by ?
the peritubular capillaries
140
What happens in the renal corpuscle ?
the production of filtrate
141
What happens in the loop of henle ?
urinary concnetration
142
What happens in the distal tubule ?
control of water and Na balance
143
What happens in the collecting duct ?
control of water and sodium balacne
144
What is the average glomerular filtration rate (GFR) ?
125mL a min
| 180 L a day
145
What does the filter cocnsit of ?
fenestrated endothelium
collagen basement membrane
epithelium of bowmans capsule which has podocyte filtration slits
146
How does the filter restrict solute movement ?
based on size and charge
147
What is the first step in the production of urine ?
production of ultrafiltrate - contains no cellulr elements or proteins (RBCs and albumin)
148
The concentrations of solutes in the ultrafiltrate is similar to ?
the plasma
149
What is filtered out of the plasma ?
all plasma constituents except for RBCs and serum albumin
150
What is proteinuria ?
the presence of proteins in the urine as they are more readily filtered
151
What is haematuria ?
the presence of RBCs in the urine
152
What are the 3 pressures that determine the overall net pressure in the bowmans capsule ?
outwards- hydrostatic pressure in glomerular capillaries
inwards
- colloid osmotic pressure
- hydrostatic pressure in the bowman's capsule
153
what does autoregulation of the GFR do?
Maintains Renal Blood Flow (RBF) & GFR within narrow limits despite Blood Pressure fluctuations
154
What are the 2 mechanisms of autoregulation of the GFR ?
myogenic response
| tubuloglomerular feedback
155
What is the myogenic response ?
arterial pressure increases the renal afferent arteriole is stretched and flow increases
vascular smooth muscle responds by contracting and thus increasing resistance
flow returns to normal
156
Where is the loop of henle situated between ?
the afferent and the efferent arterioles
157
What is communication between the tubules and the arterioles mediated by ?
macula densa- plaque of epithelial cells in loop of henle adjacent to the arterioles in the tubules- they sense flow rate
granular cells
granular cells (juxtaglomerular cells) in afferent ateriole which secrete renin)
158
What happens if there is an increase in GFR ?
flow through the tubule increases
flow past the macula dense increases
paracrine are sent from the macula densa to the afferent arterioles
the afferent atriole contricts and the efferent atriole pressure increased
hydrostatic pressure in thhe glomerulus decreased
GFR decreases
159
what happens to GFR when the afferent atreriole constricts
decreases
160
what happens to GFR when efferent ateriole constricts
increased
161
How can we measure GFR ?
by using a substance that isnt excreted or absorbed into the tubules
162
What is inulin ?
a polymer of glucose that is not indogeneous
163
What is GFR and what is it measured in ?
rate of filtrate production
| ml/min
164
What is the equation for GFR ?
Amount filtered=Amount excreted
| Pinulin x GFR=V x Uinulin
165
What are the units for the plasma and the urine concentrations of the inulin ?
mg/ml
166
What is the unit for the rate of urine production ?
ml/min
167
What are the requirements for a substance to be able to measure GFR ?
must be freely filtered at the glomerulus
must not be abosrorbed or secreted into the nephron
Must not be subject to metabolsim or produced by the kidney
Must not alter the GFR
168
What are suitable substances for the measurement of GFR ?
Creatinine and Inulin
169
What is creatinine ?
product of skeletal muscle metabolism
Amount produced is proportional to the muscle mass
constantly produced therefore constantly excreted
170
What is the need for the GFR ?
allows us to assess the perfomrance of the kidney
see any signs of kidney disease
analyse the way the kidney handles solute
171
What is the clearance rate ?
mls of plasma totally cleared of a given solutein 1 minute
172
What is the equation for clearance rate ?
Px x Cx=Ux x V
173
If there is no reabsorption no secretion what is the relationship of the CR and the GFR ?
GFR=CR
| eg. inulin
174
f there is total reabsorption and no secretion what is the relationship of the GFR and the CR ?
CR= 0
175
If there is net absorption what is the relationship between the GFR and the CR ?
Cx
176
If there is net secretion what is the relationship between the GFR and the CR ?
CR>GFR
177
What affect does diabetes have on the urine ?
Excess plasma glucose means that more glucose is filtered out of the blood- not all of this can be reabsorbed therefore theire is glucose in the urine
increased osmolarity in the tubule meas that fluid is drawn in - triggers the thirst response and more urine is produced
178
What are the anatomical features of the kidney ?
```
renal artery
renal vein
urteter
renal medulla and the renal cortex
papilla
```
179
Is the cortex or the medulla more densely supplied by the renal artery ?
cortex
180
How is urine concentrated ?
More water abosorption through the CD as it is permeable to water
increases the concentration inside the tubule and urine is hyperosmotic
181
Where is ADH produced ?
in the supraoptic and paraventricular nuclei of the thalamus
182
Where is ADH released from ?
posterior pituitary gland
183
What stimulates ADH release ?
increased plasma osmolarity
| decreased blood pressure and blood volume
184
What are the actions of ADH ?
increases permeability of the CD
increases urea permeability of the CD
increases NaCl resbsorption in the TAL
185
What is the net effect of ADH ?
increases water absorption
186
What are changes in osmolarity detected by ?
osmoreceptors in the hypothalamus
187
Where do the osmoreceptors of the hypothalamus send a message to ?
posterior pituitary to release ADH
188
If there is an increase in plasma osmolarity ?
ADH secretion increases
189
How is ADH destroyed ?
liver and the kidneys
190
What is the cellular mechanism by which ADH increases water absorption ?
ADH binds to receptors on the basolateral membrane
stimulates the production cyclic AMP from ATP by adenylyl cyclase
activates protein kinse
insertion of AQP2 channels on the CD membrane - apical cell membrane
water permability increases and water is taken into the blood
191
If ADH is present what is the condition of urine ?
ADH increases water reabsorption from the CD therefore the urine is hyperosmotic
192
What happens if ADH is absent ?
there is no stimulation of the downstream aquaporin production therefore no water reabsorption and the urine is dilute
193
What is the the role of the supraoptic and paraventricular nuclei of the hypothalamus ?
stimulate ADH secretion from the posterior pituitary
194
What happens if there is a decreased ECF osmolarity ?
ADH release is supressed
thirst response is supressed
CD not permeable
195
What is the effect of ANP on ADH ?
ANP inhibits ADH
196
What is the affect of alcohol on ADH ?
alcohol inhibits ADH
197
What is the effect of nicotine on ADH ?
nicotie promotes ADH
198
What is the main role of aldosterone ?
Aldosterone is the main hormone regualting sodiium balance
199
Where is aldosterone released from ?
Zona Glomerulosa of the adrenal cortex
200
What stimulates aldosterone ?
hyperkalaemia
low blood pressure
angiotensin II in the RAS
201
What are the actions of aldosterone ?
increase potassium secretion into the DT and the CD
Increases sodium reabsorption in the DT and the CD
leads to increased blood volume and pressure
202
What is the cellular mechanism of aldosterone action ?
Aldosterone binds to receptors in the cytoplasm
initiates transcription of sodium channels
number of sodium channels on apical surface increases
increased sodium uptake
sodium goes through the basolateral membrane into the blood and inreases blood pressure
203
What are the 3 stimuli of aldosterone ?
Increased potassium
Decreased blood pressure
Decreased flow past the macula densa
204
What is the inhibitor of aldosterone release ?
Increased plasma osmolarity
205
What are the 3 components of the juxtaglomerular apparatus ?
Juxtglomerular cells
macula densa
extraglomerualr mesangial cells
206
Where do the extraglomerular mesangial cells sit ?
between the TAL and the afferent arteriole
207
What is the mode of activity in resposne to Sympathetic activity of the heart ?
high HR
to return to normal the wall tension in the afferent arterioles decreases
sodium delivery to the macula densa decreases
low blood volume
208
What does angiotensin II do to renin ?
it acts as a negative feedback loop and stops renin release
209
What is ANP ?
anti-natriuretic peptide
210
Where is ANP produced from ?
atria when stretched
211
What is the effect of ANP ?
increases water and sodium excretion
212
What affect does ANP have on the adrenal cortex ?
it stops aldosterone release
213
What affect does ANP have on the kidney ?
stops renin
increases GFR
inhibis sodium chloride and water reabsorption
214
What is the affect of aldosterone on the hypothalamus ?
stops ADH release from posterior pituitary
215
What is secreted into the proximal tubule ?
urea and creatinine
216
What is reabsorbed in the proximal tubule ?
Glucose
proteins
aminaoacids
lactate
217
What is reabsorbed from the descending limb ?
water
218
What is secreted into the loop of henle ?
urea
219
What is absorbed from the ascending limb ?
sodium and chloride
220
What is absorbed from the distal tubule ?
ions
221
What is secreted into the distal tubule ?
protons
| ammonium ions
222
What is reabsorped from the collecting duct ?
water
| urea
223
What percentage of water and solutes of the filtrate are reabsorbed into the PCT ?
70%
224
What is the average GFR
125 ml/min
225
what are the three layer of glomerular filter
Collagen basement membrane
fenestrated enothelium
epithelium of bowmans capsule with podocyte slits
226
How does the macula dens work ?
```
increased flow past the macual densa
paracrine released from the macula densa and acts on the affferent arteriole
increases resistance
reduces hydrostatic pressure
GFR reduces
```
227
What is the normal blood osmolarity ?
290 mOsmoles
228
What is the affect of nicotine on ADH production ?
stimulates ADH
229
What are the channels that Aldosterone promotes ?
ENACC channels
| Na/K pump
230
What is reabsorbed i the proximal convuluted tubule ?
70% water and solutes
231
What is present on the apical surface of PCT ?
microvilli
232
What are the functions of the PCT ?
Reabsorption of the bulk of filtered NaCl
Reabsorption of glucsoe,amino acids
Secretion or organic molecules
pH homeostasis
233
What is the form of Na+ transport on the apical membrane ?
Na transport acorss the apical membrane is mediated by glucose and amino acids in secondary active transport
counter exchange of Na/H exchanger
234
What is the form of Na transport in the basolateral membrane ?
Na is rmeoved by the Na/K ATPase on the basolateral membrnae
this is followed by chloride and water by a paracellualr route
235
What happens in the descending limb of the loop of henle ?
Water moves out
| NaCl stays
236
What happens in the ascending limb of the loop of henle ?
Water stays
| NaCl moves out
237
What are the mechanisms of Sodium transport in the loop of henle ?
Na/Cl/L transporter
Na/H transporter - allows the acidification of urine
Na/K ATPase on the basolateral membrane
238
What happens in the DCT ?
NaCl moves out the blood and H20 stays
239
What are the mechanisms of Na transport in the DCT ?
NaCl moves into the blood
| NaCl transporter and Na?K ATPase on the basolateral membrane
240
What happens in the collecting duct
NaCl movement
241
what are the 2 types of cells in the collecting duct
principle and intercalated cells
242
what can block Na+/K+/2Cl transport in the loop of henle
loop diuretics
243
what can block Na/Cl cotransporters in the DCT
thiazide Diuretics
244
what do principal cells do
regulate ion balance based on expression of channels on the apical membrane
245
What are examples of the action of principal cells ?
aldosterone increases ENac Channels on the apical membrane
| ADH increases aquaporins on the CD membrane
246
What are the actions of intercalated cells ?
Acid/base homeostasis
247
What are the two types of intercalated cells ?
Alpha and beta
248
What is the role of alpha intercalated cells ?
excrete protons into the urine and reabsorb bicarbonate into the blood
249
What channels does the alpha intercalated cells use ?
secrete protons by the H ATPase and H/K exchanger
| Cl/HCO3 exchanger on the basolateral membrane
250
What is the role of beta intercalated cells ?
they excrete bicarbonate and reabsorb protons into the blood
251
What channels do the beta intercalated cells use ?
Cl/HCO3 exchanger
| H ATPase
252
What happens after a high water load ?
water must be excreted in excess - dilute urine that is hyposmotic to the plasma
253
What is the normal plasma osmolarity ?
290 mOsml
254
What happens after a water restriction ?
water msut be retained
| hyperosmotic urine to the plasma is produced
255
How is excretion of a dilute or concentrated urine achieved ?
by the countercurrent mechanism
256
What acts as the countercurrent multiplier ?
loop of henle
257
What acts as the countercurrnent exchanger ?
vasa recta
258
What does countercurrent flow mean ?
2 parallel limbs with fluid moving in opposite directions
259
What is the osmolarity of the PCT compared to the interstitial fluid ?
isotonic
260
What happens in the ascending limb of the loop of henle and what is the consequence
solutes move into the interstitium
| increases the osmolarity of the interstitium
261
What happens in the descending limb of the loop of henle ?
fluid becomes more concentrated as water move out to equilibrate the interstitium
262
What happens as more fluid enters the loop of henle ?
more concentrated fluid is formed in the descending limb and enters the ascending limb
a gradient forms from top to bottom in the interstitium
263
What is the condition of the fluid at the bottom of the loop of henle ?
Hypertonic as water had moved out
264
What is the condition of the fluid at the DCT ?
hypotonic as solute has moved out
265
What are the vasa recta ?
long extensions of the peritubular capilaaries
| run parallel to the loop of henle in juxtamedulalry nephrons
266
What are the functions of the vasa recta ?
water and solutes are reabsorbed by the vasa recta
| provides o2 to the medulla
267
What happens in the descending vasa recta ?
solutes move into the VR down their conc gradient
| water moves out the VR
268
What happens in the ascending vasa recta ?
water moves into the VR
| Solutes move out the VR
269
What is the role of urea ?
important for maintaining medullary concentration gradient
270
What are the 3 mechanisms of pH control ?
buffers
respiratory control
renal control
271
What happens if the metabolic rate increases ?
co2 increases - equilibrium pushed to the right
increased protons cant be buffered by bicarbonate but can be buffered by non bicarb buffers such as Hb
bicarb is much higher now and can buffer protons from non resp sources
272
what is the consequence of increased protons in metabolism being released from organic acids ?
bicarbonate can act as a buffer
273
How is respiratory control of pH carried out ?
high levels of co2 signalled by the carotid and aortic peripheral chemoreceptors and they go to the respiratory centre and signal an increased VR
274
How is pH controlled in acidosis ?
H is high in the interstitial space reacts with bicarbonate to make co2 and water which dissociates into protons and bicarbonate and the protons are excreted by a H/K ATPase
alpha intercalated cells
275
How is pH controlled in alkalosis ?
beta intercalalted cells
carbon dioxide and water in the cell are reacted into protons and bicarbonate and the cl/HC03 exchanger excretes bicarbonate into the urine
276
What does contraction of the afferent arteriole lead to ?
reduces renal blood flow and reduces GFR and hydrostatic pressure
277
What does contraction of the efferent arteriole lead to ?
reduces RBF
| increases hydrostatic pressire and increases GFR
278
What does dilation of the afferent arteriole lead to ?
increases RBF and increases GFR and hydrostatic pressure
279
What does dilation of the efferent arteriole lead to ?
increases RBF but decreases hydrostatic pressure and GFR
280
What does the macula densa do if therie is increases GFR ?
increased NaCl in the distal tubule
macual densa sense an increased flow
release paracrine that act on afferent arterioles
increases ressitance of the afferent arteriole and therefore reduce plasma flow
281
What are renal arterioles innervated by ?
sympathetic neurones
282
What are he sympathetic neurones activated in response to
fear
pain
response to fall in blood pressure
283
What does the sympathetic inenrvation cause ?
constriction of renal blood arterioles
