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Flashcards in Physiology Deck (168):
1

3 main functions of saliva
+2 others

lubrication
protection
digestion
(increases prior to emesis to neutralise
facilitates infants suckling)

2

In saliva:
___ buffer bacterial acids
____ prevents enamel demineralisation
___ coats teeth decreasing bacterial adherence
___ attacks bac cell wall
___ chelates Fe so bac can't grow
___ for immunity

HCO3 and PO4 and mucus buffer
high Ca2+ for enamel
protein coats teeth
lysozyme attacks wall
lactoferrin chelates Fe
IgA immunity

3

Enzymes in saliva and food they digest

α-amylase breaks α-1,4 bonds in carbs
lingual lipase for fats

4

In saliva NA+, Ca2+,Cl-,I-,PO4 2- are in higher/lower concn than in plasma

lower concn in slaiva

5

In saliva K+ and HCO3 - are in higher/lower concn than in plasma

higher concn in saliva

6

As rate of saliva secretion increases:
___ increases (provides optimum pH for ___) and ___ decreases

HCO3- increases ; α-amylase (neutral/alkali)
K+ decreases

7

4 organs that move with respiration

spleen
stomach
liver
gallbladder

8

Organs suspended in mesentery move ___ to line of mesentery fixation

perpendicular
in 1 plane

9

Primary secretion of saliva is from ____
it is __tonic and has a ___ composition to plasma

acinar cells
isotonic + similar in composition to plasma

10

In primary saliva secretion: Basolateral ____ drives K+ __ cell and Na+ __ cell =>
1) basolateral ____ to drive 2Cl-, 1Na+ and 1K+ __ cell
2) Cl- faciliated diffusion __ into ___ by ___

NaKATPase - K in and Na out
1) triple transporter - into cell
2) efflux into lumen by Ca2+ activated Cl- channels

11

In primary saliva secretion:
K+ into duct by ___
Na+ into duct through __causes __ to follow through _+_

apical Ca2+ activated K+ channels
Na+ through paracellular pores
H2O follows through paracellular pores + apical aquaporin 5

12

2ndry modification of saliva secretion is by _,_+_
Overall effect =
by removing __, adding __ and duct cells being impermeable to __

striated, intercalated and excretory ducts
diluting effect (more ions are removed than are added)
Na+ Cl- removed
K+ and HCO3- added
impermeable to H2O

13

Channels involved in 2ndry modification of saliva

driven by NaKATPase
K+ channel
ENaC
Na+H+exchanger
HCO3-/Cl- antiporter regulated by CFTR

14

Causes Na+ influx into apical cells in 2ndry modification of saliva:

ENaC (epithelial Na channel)
Na+H+ exchanger

15

Unconditioned reflex of saliva secretion =

chemo+mechano mouth receptors send afferents to NTS -> salivary nuclei in medulla -> parasymp. CNVII (submandibular and sublingual) CNIX (parotids)

16

Conditioned reflex of saliva secretion =

Thought/smell of food -> cerebral cortex -> salivary nuclei in medulla -> parasymp. CNVII (submandibular and sublingual) CNIX (parotids)

17

Parasympathetic supply to salivary glands causes:
1)increased synthesis and secretion of ___+__ = __
2) __ of myoepithelium mediated by __ receptors
3) __ blood flow mediated by __

α-amylase+ fluid = large volume, watery, enzyme rich secretion
contraction by M3/M1
increased by VIP

18

Sympathetic supply (in stress) to salivary glands causes:
1) increased secretion of _,_+_ = _
2)__ of myoepithelium
3) __ blood flow
mediated by

α-amylase, K+ and HCO3- = small volume, mucous-rich secretion
contraction
decreased
α and β1 adrenoceptors

19

Sympathetic supply to salivary glands is via __

thoracic via superior cervical ganglia
adrealine

20

Symp/Para usually dominates supply to salivary glands?

Parasympathetics

21

__ and ___ cause xerostomia by blocking M1/3 receptors involved in parasympathetic release of saliva

M antagonists (eg. atropine) and antidepressants

22

CN__ causes stomach to relax and expand

CNX

23

Muscle thickness ___ as go from fundus to antrum

increases

24

retropulsion =

peristalsis of stomach against closed pyloric sphincter churns food

25

Increased volume and consistency of chyme in the stomach cause the stomach to ____ causing: (4)

distend =>
Increased SM motility of stomach, activity of intrinsic nerve plexi, gastrin release and CNX activity

26

enterogastrones eg. ___ (2) are ____ that delay the release of chyme into the duodenum

CCK and secretin
hormones

27

enterogastric reflex ___ stomach emptying into duodenum via __+__

delays
intrinsic nerve plexi and autonomic NS

28

Factors in the duodenum that delay gastric emptying (4)

distension
fat
acidity
hypertonicity

29

Dumping syndrome is when:

osmotically active products of carb and protein breakdown attract water into duodenum from plasma and cause a decrease in plasma vol. and circulatory disturbance

30

Pyloric gland area in the stomach has _+_+_ cells

mucus secreting
D (somatostatin)
G (gastrin) cells

31

Oxyntic mucosa is found in _+_ of stomach
Contains _+_+_+_

fundus and body
mucus secreting
Chief (pepsinogen)
ECL (histamine)
parietal (HCl, intrinsic factor)

32

B12 is absorbed in the ___

terminal ileum

33

H+ is driven into parietal cell canaliculus by ____ on ___ in exchange for __

H+K+ATPase on apical membrane
K+

34

Inhibitors of HCl secretion in the stomach = _+_

PGE2
D cells -> somatostatin => decreased gastrin between meals

35

Stimulators of HCl secretion

Parasympathetic postganglionic nerves -> M1 on ECL and M3 on parietal
Gastrin-> parietal+ECL

36

Catalyses CO2+H20 -> H2CO3 in parietal cells
H2CO3 goes on to produce H+
and HCO3 which is basolaterally pumped out in exchange for Cl

carbonic anhydrase

37

3 stages of gastric secretion

cephalic
gastric
intestinal

38

What happens in cephalic stage of gastric secretion?

occurs before food reaches stomach
CNX -> increases ACh, histamine, gastrin, decreases somatostatin =>
INCREASES PARIETAL SECRETION

39

What happens in gastric stage of gastric secretion?

mechanoreceptors (distension) -> increase ACh secretion (for M3) and gastrin
protein digestion products increase gastrin =>
INCREASED PARIETAL SECRETION

40

What happens in intestinal phase of gastric secretion?

small intestine factors decrease acid production and low pH in stomach = somatostatin release =>
DECREASED PARIETAL SECRETION

41

Factors that protect gastric mucosa from HCl and pepsin

mucus gel layer with hydrophobic monolayer on top
PGE2 and PGI2 decrease acid secretion
mucus and HCO3- secretion
mucosal blood flow moves H+ to blood

42

H. pylori is found in ___ in stomach and causes ____ which weakens the mucus barrier

mucus gel layer
persistent inflammation

43

assimilation =

digestion+absorption

44

absorption in the GI tract =

molecules crossapical and basolateral membrane of enterocytes into interstitium

45

glucose α-1,2-fructose =

sucrose

46

glucose β-1,4- galactose =

lactose

47

oligosaccharide eg.s =

sucrose and lactose

48

brush border enzymes for oligosaccharide>monosaccharide digestion =

lactase, maltase, sucrase-isomaltase

49

intraluminal digestion of polysaccharides to oligosaccharides is by:

hydrolyisis by α-amylase

50

α-amylase is a ___enzyme meaning it only breaks ___ bonds and NOT _/_/_ bonds

endoenzyme breaks internal α-1,4 bonds
NOT α-1,6/terminal/next to branch point bonds

51

lactase is/isnt the rate limiting step in lactose assimilation

IS

52

Breaks α-1,4 bonds in oligosaccharides of

maltase

53

only enzyme to break α-1,6 bonds in oligosaccharides

isomaltase

54

absorption of the breakdown products of carb.s occurs in the ___+___

duodenum and jejunum

55

glucose and galactose are absorbed across the apical membrane in the gut by ___ by ___ with ___

2ndry active transport by SGLT1 with 2Na+

56

fructose is absorbed across the apical membrane in the gut by ___

GLUT5

57

monosaccharides are absorbed across the basolateral membrane in the gut by __ by ___

facilitated diffusion by GLUT2

58

pepsin is a __peptidase
optimum pH =
Preference for _+_ AAs
Not essential enzyme

endopeptidase
1.8-3.5
aromatic+larger neutral AAs

59

Protein digestion _/_ can be transported across apical and basolateral membrane of enterocytes

peptides
AAs

60

Locations where peptides can be broken down to AAs (3)

apical brush border enzymes
intracellular hydrolysis
luminal enzymes

61

5 pancreatic enzymes that breakdown protein in ___
endo + exopeptidases

duodenum
endo = trypsin, chemotrypsin, elastase
exo = carboxypeptidase A+B (cleave at COOH end)

62

pancreatic enzymes convert protein in duodenum to __% oligopeptides and __% AAs

70% oligopeptides
30% AAs

63

Brush border peptidases have affinity for __peptides of length
exo+/endo?

longer 3-8AAs
endo and exopeptidases (carboxy+aminopeptidases - cleave at NH3 end)

64

cytoplasmic peptidases hydrolyse ____

di/tri peptides

65

AA absorption at brush border is by:
1) 5 different ____
It is a form of ___ using E from __ on basolateral membrane
2) 2 ___ mechanisms

1) 5 Na+ co-transporters
2ndry active transport
Na+K+ATPase
2) 2 Na+ independent

66

Hartnup disease caused by:

dysfunction of 5 Na+ co-transporter mechanism for AA absorption at brush border for neutral AAs

67

Cystinuria caused by:

dysfunction of 2 Na+ independant mechanisms of AA absorption at brush border membrane for cationic AAs

68

5 mechanisms of AA transport at the basolateral membrane =

3 = efflux Na+ independent
2 = influx of Na+ dependent (AAs needed for cells nutrition)

69

Gastric phase of lipid digestion

mix with gastric lipase and slowly broken down
free FAs stimulate CCK and pancreatic lipase release

70

Secretion of bile is stimulated by __

CCK

71

__ secreted from ___ is needed to allow lipase access to FAs covered in bile salts

colipase
pancreas

72

digestion of lipids in the duodenum products =

2 FAs
2-monoglyceride

73

Absorption of FAs and monoglycerides occurs by __ in the gut

passive diffusion

74

Short and medium (less than 12C) FAs diffuse into __ when absorbed in gut
long and monos are made into _ and transported in __ to __

short+medium = villus capillaries
long+monos= tris > chylomicrons > lacteal

75

Cholesterol is absorbed from gut by ___into ___ by ___
carried by ___ to ___ where it is released and __ returned to ___

endocytosis into clatherin coated pits by NPC1L1
myosin > endocytic recylcing compartment
NPC1L1 to membrane

76

Drug that blocks NPC1L1 involved in cholesterol absorption

ezetimibe

77

Vomiting is controlled by ___ in ___ of brain

vomiting centre (VC)
medulla oblongata

78

Frequently precede vomiting

increased salivation
sweating
nausea
Increased HR

79

Vomiting:
First ___ is suspended
_____ ileum to stomach
stop ___ and close __ to prevent aspiration
__relaxes, _+_ contract to compress relaxed stomach

intestinal slow wave activity
retrograde contractions
breathing ; glottis
LOS relaxes ; diaphragm + abdominal muscles contract

80

Nausea causes relaxation of _+_ => __ in their muscles =>afferents > contraction of __+__ = contents of jej.,duo and pylorus go to _+_

stomach and LOS
tension
upper small intestine and pyloric sphincter
body and fundus

81

Things that stimulate vomiting (5)

toxins in gut/blood
mechanical
motion sickness
psychological/pain

82

In the stimulation of vomiting:
__+__ go to the CTZ in the area postrema of the brainstem

absorbed toxins in the blood (there is no BBB in CTZ)
vestibular system>vestibular nuclei (eg. motion sickness)

83

In stimulation of vomiting:
stimuli from CNS eg. psychological go to ___ and __ then to ___

cerebral cortex+limbic system
medulla

84

Toxins in the gut lumen/systemically stimulate ___cells to release __ to activate __ receptor and send a depolarising sensory afferent to the mucosa where become ___ to the ___

enterochrommafin
5-HT
5-HT3
vagal afferents
brainstem (CTZ and NTS)

85

In stimulation of vomiting:
__+__ cause signals to be sent to brainstem (CTZ and NTS)

mechanical stimuli/pathology in GI tract or other viseral organs
toxins in gut lumen or systemically

86

VC coordinates vomiting , its output is via _+_

vagus nerve
spinal motor neurones

87

VC = a group of _____ in ___ driven by ___ which receives input from ___

interconnecteed neurones
medulla
central pattern generator
NTS

88

Vagal output from VC causes... (3)

longitudinal muscle in oeso to contract and shorten
proximal stomach relaxes
small intestine = retrograde contraction

89

somatic motor neurones from VC cause ... (2)

anterior abdominal and diaphragm contract

90

autonomic/ somatic efferents from VC cause ... (4)

Heart rate and force increase
increase salivary secretions
pale and clammy skin
anal and bladder sphincters contract

91

Consequences of vomiting =

dehydration
hypokalaemia (due to HKATPase)
loss of H+ and Cl- => hypochoraemic metabolic alkalosis
Mallory-Weiss tear
Rarely - loss of duodenal HCO3- =metabolic acidosis

92

Chemo and radiotherapy cause vomiting due to __

5-HT and substance P from enterochrommafin cells

93

___ for parkinsons stimulates vomiting by agonising __

levodopa
D2 receptors in CTZ

94

Plicae circulares in small intestine synonym =

folds/valves of Kerckring

95

2 eg.s of incretins and where they are secreted from
function =

GIP - K cells in duod and jej
GLP-1 - L cells in small int
stimulate β cells in panc to produce insulin

96

Secretin is secreted from ___
function =

S cells in duodenum
stimulates release of pancreatic, bile release and CCK
chief cells -> pepsinogen

97

Motilin is secreted from ___
function =

M cells in duodenum and jejunum
stimulates muscle contractions to clear food to colon

98

CCK is secreted from ___
function =

I cells in duo + jejunum
decreases gastric emptying, HCl
Increases pancreatic and bile release

99

Gastrin is released from ___
function =

G cells of antrum (mainly) and duodenum
HCl release
antrum contractions
decreased rate of gastric emptying, pancreatic + gallbladder secretions

100

Ghrelin is released from ___

Gr cells in antrum, small intestine and elsewhere eg. pancreas

101

All peptide hormones secreted from the small intestine act on ___ receptors

G-protein coupled

102

succus entericus from the small intestine contains:

mucus (goblet cells)
aqueous salts (crypts of Lieberkuhn, no enzymes

103

Succus entericus:
Cl- out via ___ and _+_ follow
excessively activated in __
control mechanisms =

CFTR
H2O and Na+
diarrhoea - cholera
distension/irritation, gastrin, CCK and para (increases)
sympathetic (decreases)

104

___ in ___ ileum stimulates gastroileal reflex

gastrin
empty ileum

105

due to segmentation food takes ___ to move through small intestine

3-5 hrs

106

strength of segmentation in small intestine increases with ___ and decreases with __ stimulation

increase = para
decrease = symp

107

In fasting state peristalsis =
1)
2)

1) few localised contractions
2) MMC - every 90-120mins - clears debris

108

MMC controlling factors =

decreased by: feeding, vagal, gastrin, CCK
increased by motilin (macrolides mimic)

109

Enzymes in zymogen granules in pancreatic acinar cells =

pancreatic amylase and lipase

110

Pancreatic acinar cells secrete:

pancreatic amylase and lipase
trypsinogen
chymotrypsinogen and procarboxypeptidase A+B

111

chymotrypsinogen + Procarboxypeptidase A+B are activated by ___
trypsinogen is activated by ___

chymo + procarb - trypsin
trypsinogen - duodenal enterokinase from mucosal cells

112

Duct cells in pancreas secrete ___ rich fluid (_+_ follow through pores)
___ pumps out Cl- used to drive ____

HCO3-
Na+ and H2O
CFTR drives Cl-/HCO3- antiporter

113

cephalic phase of pancreas exocrine control

vagal nerve stimulates acinar cells (20% of secretion)

114

gastric phase of pancreas exocrine control

distension>vasovagal reflex> para stim.s acinar and duct cells (5-10%)

115

intestinal phase of pancreas exocrine control

acid> secretin> duct cells> increased aqueous NaHCO3-
fat+protein > CCK>acinar>more enzymes
(70-75%)

116

Length and diameter of colon =

1.5m
6cm

117

ileocaecal valve is controlled by:

vagal, symp and enteric neurones

118

Functions of the large intestine

absorb: H2O, Na+, Cl-, short chain FAs (bac fermentation of undigested carb
secrete: K+, HCO3- and mucus
storage
excretion

119

Mass movements in the colon (2)

1) asc and transverse - caused by gastrocolic response - gastrin+extrinsic nerves in response to food: 1-3x daily
2) distal colon - may trigger defaecation reflex

120

rectosphincteric reflex =

distension of rectum > active contraction of rectal SM > internal anal sphincter relaxes

121

Functions of colonic flora

immunity
motility promotors
mucosal integrity
obstruction
synthesis vitamin K2 and FAs
activate some drugs

122

Hirschprung's disease =

congenital megacolon
colon lacks part of enteric NS and causes obstruction/severe constipation

123

composition of faeces =

100ml H2O
50ml cellulose, bilirubin and bacteria

124

Diarrhoea = loss of fluid and solutes from GI tract in excess of ___

500ml per day

125

Absorption of H2O in gut is ___ and driven by ___

passive
transport of solutes

126

Gut secretes ___l per day of fluids
small intestine absorbs __l
colon absorbs ___

9.3l
8.3l
90% of the litre left

127

Main cause of postprandial Na+ absorption =
location =

Na+/glucose and Na+/AA cotransporters
in small intestine (mostly jejunum)

128

Na+/glucose and Na+/AA cotransporters are a form of ___ as function with Na+K+ATPase on the basolateral membrane.
They are ___ and so make the lumen ___ and drive __ into interstitium
not regulated by

2ndry AT
electrogenic
-ve
Cl-
NOT regulated by cAMP or Ca2+

129

Na+/H+ exchange (without a parallel Cl-/HCO3- exchanger) occurs in the ___ and is stimulated by ___

duodenum and jejunum
HCO3- in the lumen

130

Parallel Na/H+ and Cl-/HCO3- exchange occurs in the ___ and is most involved in H2O absorption in ____

ileum and proximal colon
interdigestive period

131

Parallel Na/H+ and Cl-/HCO3- exchange is regulated by:
is electroneutral/genic

increased cAMP, cGMP, Ca2+ decrease NaCl absorption

132

E. coli enterotoxin activates ___ to produce ___ which inhibits Parallel Na/H+ and Cl-/HCO3- exchange and so decreases NaCl absorption and causes ___

adenylate cyclase
intracellular cAMP
diarrhoea

133

Na transporter in distal colon =
is stimulated by ____ which (3)

ENaC
aldosterone (NOT cAMP or cGMP)
opens ENaC
increases no. of ENaC on membrane from intracellular pool
increases ENaC + NaKATPase synth

134

Na transporters involved in water balance in the GI tract =

Na+/glucose Na+/AA co-transporters
Na+/H+ exchanger (w/wo parallel Cl-/HCO3- exchanger)
ENaC

135

Passive Cl- absorption in the gut is driven by ___ due to
___ small intestine
___ colon

-ve potential
Na+/glucose+AA transporter = small intestine
ENaC = colon

136

In the gut Cl- secretion is greater/less than absorption
It is secreted from __ cells

less than
crypt cells

137

Basolateral transporters involved in Cl- secretion

NaKATPase (causes low Na intracellularly) drives
NKCC1 to pump inwards (increases Cl- intra concn)
IK1+BK (recycle/efflux K+ )

138

Apical transporter for Cl- secretion in gut
Is indirectly activate by ___

CFTR
enterotoxins eg. choler, E. coli, C. diff
hormones and neurotransmitters eg. VIP, bradykinin 5-HT
immune cell products eg. PG and histamine
laxatives

139

Secondary messengers that activators of CFTR stimulate to activate CFTR

cAMP (cholera toxin, VIP and histamine)
cGMP (E. coli toxin and guanylin)
Ca2+ (ACh, bradykinin, 5-HT)

140

Main electrolyte driver of H2O absorption in the gut =

Na+

141

Diarrhoea causes (3) due to loss of fluid and electrolytes

dehydration (na+ and H2O)
metabolic acidosis (HCO3-)
hypokalaemia (K+)

142

Mechanisms behind causes of diarrhoea (4)

hypermotility
non/poor absorption of solutes in intestinal lumen
impaired absorption of NaCl
Excess secretion

143

Treatment of diarrhoea =

fluids and elctrolytes
may need anti-infective agents
may need anti-motility eg. opiates or loperamide

144

Diarrhoea caused by impaired absorption of NaCl eg.s

congenital chloridorrhea = no exchanger
inflammation
infection (E. coli, campylobacter toxins)
excess bile acid in colon

145

Vitamin D is activated by __

liver

146

hepatocytes are arranged between sinusoids in plates _ cells thick

2

147

Basolateral membrane of hepatocytes faces the ___
which lies between it and the endothelial cells of sinusoid

pericellular space (of Disse)

148

apical membrane of hepatocyte is __+ forms

groove
forms canaliculi

149

stellate/__ cells store __ and are found in the ___

Ito
vitamin A
space of Disse

150

Intrahepatic biliary system = canaliculi> terminal bile ductules >___ ducts > ___ ducts>___ducts>__ ducts>R+L hepatic ducts

perilobular
interlobular
septal
lobar

151

_-__l of bile is produced each day

0.6-1.2l

152

__+__ are stimulated by chyme in duodenum to cause gallbladder SM to contract
___ opens the sphincter of Oddi

CCK and CNX
CCK

153

75% of bile comes from secretions from __
25% from __

75% = hepatocytes
25% = bile duct cells

154

bile duct cell secretion is similar to __secretion and properties =

pancreatic
alkaline
aqueous Na+ K+ Cl- HCO3- rich

155

Between meals bile duct cell secretion is similar to __ in ionic composition
during meals flow rate ____ due to secretin and __ transporter activity ___ so HCO3- content ___

plasma
increases
HCO3-/Cl-
increases
increases HCO3- content during meals

156

Bile secretions that are produced in hepatocyes =

primary bile acids - mainly cholic and chenodeoxycholic acids, H2O and electrolytes, lipids, phosholipids, cholesterol, IgA and bilirubin

157

bilirubin is from ___ of RBCs

porphyrin

158

primary bile acids + __ = bile salts
many are conjugated to __/__

Na+ or K+
glycine/taurine

159

__% of bile salts are recycled. The reabsorption occurs in the __

95%
terminal ileum

160

Ileum bile salt transporter = __
on liver transporter for influx = ___
on liver transporter for efflux to gallbladder/duod =__

ASBT (Na+ coupled)
NTCP (Na+ coupled)
MRCP2+ABCG2 pumps

161

Secretin stimulates a ____ bile secretion

aqueous alkaline

162

Relief of biliary colic =

atropine/GTN

163

Analgesics for biliary colic = __

morphine (but constricts sphincter of Oddi)
buprenorphine
pethidine

164

more/less polar drugs are excreted by the kidney

more polar

165

Liver metabolises __ to active form
and __ to increased activity form ___

ACEIs
codeine-> morphine

166

Phase 1 in liver metabolism of drugs =

make drug more polar + make handle for conjugation = functionalisation

167

In phase 1 drug metabolism oxidation is mediated by ___ and is for ___ drugs

CYP family of monooxygenases
lipid soluble

168

Phase 2 of drug metabolism in the liver = ___ with __
it increases the ___ and so usually leads to __ products

conjugation with glucaronyl/sulphate/methyl/acetyl
increases polarity
inactive products