Physiology Flashcards
1
Q
components of alimentary canal
A
mouth/oropharynx oesophagus stomach small intestine large intestine rectum and anus
2
Q
4 functions of alimentary canal
A
motility
secretion
digestion
absorption
3
Q
describe lumen during circular muscle contraction
A
narrowed lumen and longer
4
Q
describe lumen during longitudinal muscle contraction
A
shorter, fatter intestine
5
Q
how is a synchronous wave of contraction achieved in the smooth muscle of the GI tract
A
gap junctions between cells
6
Q
how is GI smooth muscle contraction driven
A
pacemaker cells
7
Q
what do interstitial cells of cajal do?
A
drive slow waves coupled to smooth muscle to control rate of contraction
8
Q
when does intestinal muscle contraction occur
A
when slow waves exceed threshold to contract
9
Q
what increases force of contraction in intestinal muscle
A
number of APs discharged
10
Q
true/false - frequency of slow waves vary along GI tract
A
true
11
Q
where do parasympathetic nerves for the GI tract originate from
A
vagus nerve sacral outflow (S2-S4)
12
Q
true/false - preganglionic parasympathetic fibres of the GI tract synapse with gaglia and connect to postganglionic neurons of parasympathetic system
A
false - synapses with ganglia then connects to postganglionic neurons of ENS
13
Q
true/false - preganglionic neurons of the sympathetic system synapse at the sympathetic chain
A
false - they synapse at prevertebral ganglia
14
Q
inflences of parasympathetic nervous system
A
increased gastric, pancreatic and small intestine secretion
increased blood flow and smooth muscle contraction
relaxation of sphincters
15
Q
influences of sympathetic nervous system
A
increased sphincter tone
decreased motility, secretion and blood flow
16
Q
true/false - ANS/hormones can modulate myenteric and submucosal plexus
A
true
17
Q
what is peristalsis
A
wave of relaxation followed by contraction in aboral direction
18
Q
in peristalsis, what happens behind the bolus
A
NO/VIP cause longitudinal muscle to relax
ACh causes circular muscle to contract to push bolus
19
Q
in peristalsis, what happens in front of the bolus
A
longitudinal muscle contracts due to ACh
circular muscle relaxes due to VIP/NO
20
Q
what is colonic mass movement
A
sweeping contraction that forces faeces into rectum
21
Q
function of upper oesophageal sphincter
A
relaxes to allow swallowing and closes in inspiration
skeletal muscle
22
Q
function of lower oesophageal sphincter
A
relaxes to allow food entry to stomach
prevents acid reflex into oesophagus
23
Q
function of pyloric sphincter
A
regulates gastric emptying and prevents duodenal gastric reflux
24
Q
function of ileocaecal valve
A
controls flow from ileum to caecum
ileal distention opens it and proximal colon distention closes it
25
internal and external anal sphincters
defaecation reflex
| skeletal muscle - voluntary control
26
function of orad stomach
accomodate food in feeding
| digestion by amylase
27
what effect does vagal tone have on the orad stomach
relaxation to allow for storage of ingested food
| tonic contraction to propel food into caudad stomach
28
what is the orad stomach made up of
fundus and proximal body
29
what is the caudal stomach made up of
distal body and antrum
30
function of caudad stomach
digestion by pepsin and HCl, intrinsic factor and gastrograffin
phasic peristaltic contractions to allow chyme into duodenum
31
what is retropulsion
rebound of chyme back into caudad stomach due to faster contraction than chyme movement - churns chyme
32
gastric factors controlling stomach emptying
```
stretch of smooth muscle
intrinsic nerve plexus stimulation
increased vagal activity
increased gastrin
thicker chyme
```
33
duodenal factors controlling stomach emptying
enterogastric reflex - decrease in antral activity due to decrease in ANS and intrinsic nerve plexus
release of enterogastrones from duodenum to inhibit contraction
34
stimuli for slower secretion of chyme into stomach
high fat
high acid concentration
hypertonicity - carbohydrates and protein
duodenal distention
35
what is the oxyntic gland area
fundus and body
36
what is the pyloric gland area
antrum
37
secreting cells and their secretions in the pyloric gland
G cells - gastrin
D cells - somatostatin
Mucus secretion
38
secreting cells and their secretions in the oxyntic gland
enterochromaffin - histamine
parietal cells - HCl, intrinsic factor, gastroferrin
Chief cells - pepsinogen
Mucus secretion
39
Function gastrin
stimulates gastric secretion and acid production
growth of gastric mucosa
G cells
40
function somatostatin
reduces astric secretion and acid production
41
function HCl
denatures proteins, kills microorganisms, pepsinogen to pepsin
42
function intrinsic factor
binds to vitamin B12 to facilitate absorption, sometimes iron
43
function gastroferrin
binds to iron to facilitate absorption
44
function pepsinogen
inactive precursor of pepsin, once activated it can further activate pepsin
45
function histamine
stimulates HCl secretion
46
describe HCl secretion by parietal cells
CO2 and H2O combine by carbonic anhydrase to form carbonic acid. dissociates to H, pumped into canaliculus by proton pump. bicarbonate removed by antiport with chloride, which leaves cell by CFTR at canaliculus
47
true/false - acid secretion is a passive process
false - it is active
48
name 3 secretagogues
ACh
Gastrin
Histamine
49
where does the proton pump translocate from on stimulation by secretagogues
cytoplasmic tubulovesicles
50
what is the cephalic phase of acid secretion and what drives it
anticipatory signal telling stomach to secrete acid
| driven by vagus nerve
51
Vagus nerve stimulates enteric nervous system to release ACh in the cephalic and gastric phase. what does it do?
parietal cells- increase secretion
D cells - reduce somatostatin
ECL - increase histamine
(GRP not ACh) G cells- increase gastrin
52
what is the gastric phase, and besides vagal innervation what else drives it
when food enters stomach
distention of stomach
amino acids on g cell to increase gastrin
high pH decreases somatostatin
53
what drives acid secretion in the intestinal phase
chyme enters duodenum to cause weak gastric secretion stimulation
54
what causes decreased acid secretion in cephalic phase
decreased vagal activity
55
what causes decreased acid secretion in gastric phase
decreased vagal activity
low pH - somatostatin from D cells
PGE - reduce histamine and gastrin mediated HCl
56
3 ways small intestine increases surface area and better absorption
circular folds of kerckring
villi
microvilli
57
what is segmentation and when does it occur
digestive state
| vigorous alternating contraction and relaxation of segments of circular muscle
58
cause of segmentation and how to increase strength
interstitial pacemaker cells emitting slow waves, reach threshold upon distention
Parasympathetic innervation
59
what is the gastroileal reflex
segmentation in empty ileum due to gastrin from stomach
60
what is the migrating motor complex
strong peristaltic contraction that passes slowly across small intestine to clear debris, mucus and cells every 90-120 mins
61
___ and ___ induce the MMC and ___, ___ and ___ inhibit it
increase- motilin, macrolides
| decrease - vagus, gastrin, CCK
62
location of secretin secretion and function
S cell duodenum
| promotes secretion of bicarbonate from pancreas and gallbladder due to protons/fatty acid
63
location of CCK secretion and function
I cells duodenum
inhibits gastric emptying and pancreatic enzyme secretion, contraction of gallbladder and relaxation of sphincter oddi due to monoglycerides, fatty acid, amino acids
64
location of GIP secretion and function
K cell duodenum, jejunum
| insulin release and impaired gastric emptying due to glucose, amino acids, fatty acids
65
location of GLP-1 secretion and function
L cell small intestine
insulin secretion
inhibits glucagon secretion
decrease gastric emptying and appetite
66
location of motilin secretion and function
M cells duodenum and jejunum
| stimulates MMC on fasting
67
location of ghrelin secretion and function
Gr of gastric antrum, small intestine
| stimulates appetite
68
innervation for succus entericus
```
distention
gastrin
CCK
secretin
parasympathetic activity
```
69
contents of succus entericus
mucus - goblet cell
| aqueous salt - crypt lieberkuhn - secreted by chloride ion secretion into lumen by CFTR, drawing Na and H2O
70
2 endocrine pancreatic secretions
insulin
| glucagon
71
describe how digestive enzymes converge in pancreatic duct
acinar cells secrete digestive enzymes that travel from acinus to duct and then converge
72
describe the formation of bicarbonate by pancreatic duct cells
Na/Cl transporter provides some bicarbonate
CO2 into cell with H20 and carbonic anhydrase produces carbonic acid
H dissociates and is pumped out by proton pump and Na/H transporter
bicarbonate secreted in bicarbonate/Cl exchanger with CFTR pumping chloride back out
73
what enzyme catalyses trypsinogen to trypsin
enterokinase
74
trypsin in active form activates what other proteases
chymotrypsin and carboxypeptidase A&B
75
what increases pancreatic secretion in cephalic phase
vagal stimulation
76
what increases pancreatic secretion in gastric phase
gastric distention leading to vagal stimulation
77
what increases pancreatic secretion in intestinal phase
acid in duodenum - increased secretin
| fat and protein - increased CCK
78
what is luminal digestion
enzymes secreted into lumen
79
what is membrane digestion
enzymes present at brush border of epithelial cells
80
what is assimilation
the collective term for digestion and absorption
81
what linkage does amylose have
straight chain with alpha-1,4 linkage
82
what linkage does amylopectin have
branched chain with alpha-1,4 and alpha-1,6 linkage
83
what linkage does glucose have
alpha-1,4
| alpha-1,6
84
name 2 oligosaccharides
sucrose - glucose and fructose
| lactose - glucose and galactose
85
name 2 monosaccharides
glucose
| fructose
86
true/false - dietary carbohydrates must be converted to monosaccharides for absorption
true
87
where are polysaccharides broken down
intraluminal digestion - pancreatic enzymes and alpha amylase
88
what does alpha amylase break down
internal alpha-1,4 links but not terminal links so can only yield oligosaccharides
89
where are oligosaccharides broken down into monosaccharides for absorption
brush border
90
what does maltase do
degrades alpha 1,4 linkage in straight chain oligomers
91
what does sucrase do
hydrolyses sucrose to glucose and fructose
92
what does isomaltase do
splits branches of alpha 1,6 links of alpha limit dextrins
93
where does carbohydrate absorption occur
duodenum and jejunum
94
how do glucose and galactose move into enterocyte from lumen
SGLT1 - secondary transport
| 2 Na pumped in per one glucose/galactose
95
how does fructose enter enterocyte
GLUT5 - facilitated diffusion
96
how do monosaccharides leave enterocyte at basolateral membrane
GLUT2
97
in what state must digested proteins be to be absorbed by small intestine
oligopeptides and amino acids
98
what digests proteins in the stomach
pepsin and HCl
99
what digests proteins in the duodenum
trypsin, chymotrypsin, elastase, procarboxypeptidase A&B
100
true/false - there are a limited selection of brush border peptidases
false- there are many
101
what do cytoplasmic peptidases do?
hydrolyse dipeptides and tripeptides
102
describe protein absorption at the brush border
7 mechanisms of uptake - 5 require sodium and 2 dont
103
what is system B0AT1
Na dependent uptake of neutral amino acids
104
what is system b0+AT
Na independent uptake of cationic amino acids
105
mechanisms of uptake at basolateral membrane
3 efflux and 2 influx
106
what facilitates uptake of di,tri,tetra peptides at brush border
pepT1
107
what happens to oligopeptides following brush border absorption
further hydrolysed to amino acids and then transported out of enterocyte
108
lipids are poorly soluble on their own and so must form an emulsion to be properly digested and absorbed. what makes it up
chewing
gastric churning/segmentation/peristalsis
pancreatic/biliary secretion
109
what enzyme digests TAGs in the stomach and what are the products
gastric lipase
| diacylglycerol and free fatty acid
110
what enzyme breaks down TAGS in the duodenum and what are the products
pancreatic lipase
| monoacylglycerol and 2 free fatty acids
111
what stimulates the release of pancreatic lipase and bile
CCK
112
functions of bile salts
stabilise fat vesicle by acting as detergent
| increase SA of lipid to pancreatic lipase
113
what allows pancreatic lipase access to hard to reach TAGs in the lipid micelle and how is it secreted
colipase, secreted as procolipase and activated by trypsin
114
waht does failure to secrete bile salts result in?
steatorrhoea
| secondary vitamin deficiency
115
what state must lipids be in, in order to be absorbed
fatty acids
| monoacylglycerol
116
describe absorption of short chain fatty acids
diffuse/transported into enterocyte and exit through basolateral membrane to enter villus capillary
117
describe absorption of long chain fatty acids
diffuse/transported into enterocyte and resynthesised to TAG and synthesised to chylomicron
exocytosed
118
describe cholesterol uptake
NPC1L1 endocytoses cholesterol and is recycled to be put back onto cell membrane, dependent on amount of cholesterol in cell
119
calcium absorption is passive in _____ and active in ____ and _____
small intestine
| duodenum and jejunum
120
what increases calcium absorption
dihydroxyvitamin D3 and parathyroid hormone
121
Absorption of iron is regulated/unregulated and loss of iron is regulated/unregulated
regulated
| unregulated
122
in what form is most digested iron found
ferric (3+)
123
where would ferric iron be found and in what form
meat and veg
inorganic iron
haem
ferratin
124
before ferric iron can be absorbed by an enterocyte what must happen
it must accept an electron to pass into the cytoplasm to become Fe2+
125
what promotes electron acceptance in Fe?
HCl, vitamin C, gastroferrin, duodenal cytochrome B
126
Fe influx is via _____
DMT1
127
function of apoferratin
chaperone molecule to store iron at ferratin
128
function of mobilferrin
chaperone molecule transferring iron to basolateral membrane for efflux
129
how does iron exit cell via basolateral membrane
ferroportin 1
130
when iron 2+ exits cell what must it be converted to
ferric iron
131
how is haem converted to Fe 2+ for use in the enterocyte
haem oxidase converts it for binding with mobilferrin apoferrin
132
where is vitamin B12 found
food, and bound to protein
133
describe absorption of B12
HCl liberates from protein and binds it to haptocorin
| intrinsic factor binds to B12 after haptocorin digested by pancreatic proteases
134
where is B12 absorbed
terminal ileum
135
describe absorption of fat soluble vitamins
incorporated into micelles and transported into enterocytes
| incorporated into chylomicrons and distributed by lymphatics
136
how are water soluble vitamins absorbed
Na dependent/independent manner
137
vitamin C&H are Na dependent/independent
dependent
138
folic acid is Na dependent/independent
independent
139
true/false - the internal and external anal sphincters are fully separate
false - the external surrounds the internal
140
what are the haustra
sac like bulges due to circular muscle and tenia coli
141
what allows for chyme to pass from ileum to caecum
duodenal distention causes ileocaecal valve to relax
| gastrin and CCK
142
what does the colon have to make up for its lost surface area due to lost villi
colonic folds
crypts
microvilli
143
function of colonocytes
mediate ion absorption to allow for water absorption
144
function of crypt cells
mediate ion secretion
145
what ion changes does aldosterone cause
increased Na absorption and K secretion
146
what is contained in faeces
```
cellulose
bacteria
bilirubin
salt
water
```
147
what is haustration and when is it present
alternating contraction of smooth muscle, segmentation with less frequency
disappear before and reappear after mass movement
148
what is mass movement
driving of faeces distally by contraction of large sections of circular muscle
149
what triggers mass movement
gastrocolic response
150
describe rectal stretch leading to defaecation
rectal stretch sends afferent via spinal cord, efferent causes smooth muscle contraction in sigmoid colon and rectum to allow defaecation
151
describe rectal stretch in delaying defaecation
efferent signal sent to brain to notify need to defaecate, efferent causes relaxation of external anal sphincter to cause defaecation or allows for delay as voluntary muscle
152
3 functions of intestinal flora
intestinal immunity by competition
activation of certain drugs
promotes motility and mucosal integrity
153
where does flatus come from?
swallowed air
| bacteria attacking indigestible carbohydrates
154
what is linaclotide and how does it work
peptide drug for moderate/severe IBS
| increased chloride and bicarbonate secretion to ease constipation
155
what is used for the acute and mild treatment of IBD
glucocorticoids - acute
| aminosalicylates - mild
156
how is water and Na absorbed in jejunum in the postprandial period
Na/glucose and Na/amino acid
| ion flow into cell drags water with it and creates -ve transepithelial potential
157
how is water and Na absorbed by jejunum in the interdigestive period
Na/H exchange
| occurs at alkaline environment due to pancreas releasing bicarbonate
158
how is water absorbed in ileum and proximal colon and what is it regulated by
Na/H and Cl/HCO3
| cAMP, cGMP, Ca - cause less NaCl absorption
159
what mediates water uptake in distal colon and describe its regulation
ENaC
| increased by aldosterone, opening ENaC, inserting more in membrane and increasing synthesis
160
how is Cl absorbed by small and large intestine
small - -ve driving force due to Na/Amino acid/glucose channel draws up
Large - -ve driving force from ENaC
161
where is Cl secreted from and what increases secretion
```
CFTR
bacterial enterotoxins
hormones and neurotransmitters
immune cell products
laxatives
```
162
causes of diarrhoea
```
infection
chronic disease
toxins
drugs
psychosocial factors
```
163
physiological cause of diarrhoea
hypermotility
impaired NaCl absorption
poorly absorbable substances
excessive secretion
164
describe how cholera causes secretory diarrhoea
toxin enters enterocyte to inhibit GTPase
increased cAMP and CFTR stimulation, release of Cl
further release of cAMP and Na uptake impaired so less water absorbed
165
function of the liver in carbohydrate metabolism
gluconeogenesis
glycolysis
glycogenesis
glycogenolysis
166
function of the liver in fat metabolism
synthesis of cholesterol and lipoproteins
ketogenesis
process chylomicrons
167
function of the liver in protein metabolism
synthesise plasma proteins
transamination/deamination of AA
convert ammonia to urea
168
what hormones does the liver activate
conversion of thyroid hormone
| conversion of vitamin D
169
what hormones does the liver deactivate
insulin
glucagon
ADH
steroid hormones
170
what does the liver store
glycogen
copper
iron
fat soluble vitamins
171
what proteins does the liver synthesise
```
coag factors II, VII, IX, X
proteins C and S
albumin
complement factors
carrier proteins
apolipoproteins
```
172
what expogenous substances does the liver detox
ethanol
| drugs
173
what endogenous substances does the liver detox
bilirubin
174
what protection does the liver offer
immune factor production
| kupffer cells destroy old RBC and bacteria
175
what cells produce bile
hepatocytes
| cholangiocytes
176
describe how bile exits the biliary tree to enter the duodenum during a meal
chyme stimulate vagus and CCK to release bile
| gallbladder contracts and sphincter of oddi opens
177
what is the function of bile
forms micelle with fat
acid neutralisation
pH optimisation
mucosal protection
178
primary and secondary bile acids?
primary - cholic acid and chenodeoxycholic acid
| secondary - deoxycholic and lithnocholic acid
179
true/false - gallstones are painful so give morphine
false - morphine can make the pain worse
| give Buprenorphine
180
describe reuptake of bile salts
active in ileum and passive in rest of small intestine
| returned to liver in portal circulation and undergo enterohepatic recycling
181
name 3 bile acid sequestrants, indication and imitation
colveselam, colestipol, colestyramine
hyperlipidaemia, cholestatic jaundice
bile acid diarrhoea
large dose, cause diarrhoea, reduce vitamin absorption
182
phase II drug metabolism is ___ and often occurs by ____
conjugation
| glucuronidation
183
what is cytochrome P450 monooxygenases
haem proteins in ER of hepatocytes mediating oxidation
184
how does hepatic encephalopathy occur
hepatic failure causes failure of ammonia detox
| toxic effect on CNS
185
therapy for encephalopathy
lactulose - converts NH3 to NH4 to prevent reabsorption
| rifamixin - suppress colonic flora to prevent ammonia generation
186
characteristics of nausea
```
feeling sick
pallor
sweating
salivation
reverse peristalsis and upper stomach and lower oesophagus relaxation
```
187
what is retching
rhythmic reverse peristalsis of stomach and oesophagus
188
what is vomiting
forceful expulsion of gastric/intestinal contents out of mouth
189
true/false - in vomiting the stomach is contracted
false - it is relaxed
190
events of vomiting
suspended slow waves
retrograde contraction from ileum to stomach
closure of glottis
relaxed LOS, contracted diaphragm and abdomen
ejection of gastric contents
191
how do toxic materials stimulate vomiting
stimulate enterochromaffin cells to release 5-HT - depolarises vagal afferents to reach NTS and CTZ
192
what does the vestibular system pathway stimulate to invoke vomiting
CTZ
193
what do stimuli within brain act on to stimulate vomiting
vomiting centre directly
194
vagal efferents from VC
shortened oesophagus
proximal gastric relaxation
retrograde contraction
195
somatic motor from VC
contracted diaphragm and anterior abdomen muscles
196
autonomic efferent from VC
cold sweat, pallor, increased saliva
tachycardia
anal/bladder sphincter contraction
197
consequences of severe vomitjng
dehydration
metabolic alkalosis due to loss of H and Cl
Metabolic acidosis due to bicarb loss - rare
hypokalaemia
mallory weiss tear
198
causes of drug induced emesis
```
cancer chemotherapy/radiotherapy
operation with general anaesthetic
agents with dopamine agonist properties
morphine and opiates
cardiac glycosides
drugs enhancing 5-HT - SSRI
```
199
indication for ondansetron, palonosetron
chemotherapy/radiotherapy emesis
less effective over time
not indicated for motion sickness
200
name an NK1 antagonist and what it is given with
aprepitant
| 5-HT3 antagonist and dexamethasone to treat highly emetogenic chemo
201
when is domperidone/metoclopramide given, class, indication, contraindication
dopamine receptor antagonist in CTZ
drug induced vomiting esp parkinsons
domperidone less unwanted effects
contraindicated motion sickness and children
202
name 2 H1 antagonists, action and side effect
```
cyclizine/cinnarizine
block H1 receptors in vestibular nuclei and NTS
drowsiness
slight muscarinic action
effective motion sickness
```
203
name 2 muscarinic ACh receptor antagonists, indication, side effects
hyosine/scopolamine
motion sickness
blocks muscarinic receptors in vestibular nuclei, NTS, VC
inhibits GI movements
blurred vision, dry mouth, urine retention
