Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MD3002 > GI physiology > Flashcards

GI physiology Flashcards

1
Q

what is the digestive purpose of the mouth

A

chewing
moistens and lubricates food
begins digestion of polysaccharide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the purpose of the small intestine

A

digestion and absorption of most substances

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the purpose of the large intestin

A

storage and concentration of undigested matter
salt and water absorption
defecation
vitamin K absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is the purpose of the pancreas

A

secretion of enzymes and bicarbonate in order to digest carbs, fats, proteins and nucleic acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the purpose of bicarbonate

A

to neutralise HCl entering the small intestine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the purpose of bile

A

solubilise fats

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is the purpose of the liver

A

bile
bicarbonate
eliminate waste products and trace metals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the purpose of the gall bladder

A

store and concentrate bile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the 5 main physiological processes of the GI tract

A 
motility
secretion
digestion
absorption 
excretion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what are the defence mechanisms of the gut

A

Gut associated lymph tissue GALT
organised aggregates of lymphoid tissue- Peyer’s patches
immune cells- lymphocytes and mast cells

gastric acid, mucin, peristalsis and epithelium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is the lamina propria

A

loose connective tissue with cappilaries, neurones and immune cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is the muscularis mucosae

A

thin smooth muscle layer of the mucosa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

where is striated muscle found

A

pharynx, upper oesophagus and external anal sphincter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how is food moved along the GI tract

A

rhythmic contraction and relaxation of GI wall and sphincters

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what muscle types surround the myenteric plexus

A

circular and longitudinal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what type of smooth muscle is found in the GI tract

A

single unit

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what does Ca2+ bind to in order to initiate contraction

A

calmodulin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

how do neuronal and hormonal inputs affect contraction

A

change the force of contraction but not the speed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what links adjacent cells in single unit smooth muscle

A

gap junctions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what does calcium calmodulin do

A

activates inactive myosin light chain kinase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what does the active myosin light chain kinase do

A

phosphorylates myosin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what does latch state contraction do

A

maintains high tension

maintains the cross bridge binding with low atp consumption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

how does smooth muscle relax

A

decrease in Ca2
leads to dissociation of Ca- calmodulin which leads to inactivation of myosin light chain kinase
which leads to dephosphorylation of myosin
cross bridges break

myosin phosphatase removes phosphate from the myosin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what causes slow waves in smooth muscle

A

interstitial cells of Cajal which are pacemaker cells found in the myenteric plexus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is the intrinsic rate of the pacemaker cells

A

3-12 per minute

3 in the stomach
12 in the duodenum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what are the stages in slow wave generation

A

Depolarisation due to the cyclical opening of voltage
gated Ca2+ channels
1. Increase in the intracellular Ca2+ concentration
2. Opening of Ca2+ dependent K+ channels
3. Increased K+ permeability leads to slow
hyperpolarisation
4. Voltage gated Ca2+ channels close and intracellular
Ca2+ concentration falls
5. Ca2+ dependent K+ channels close
6. Voltage gated Ca2+ channels open

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what stimulates the spikes in membrane potential

A

stretch
acetylcholine
parasympathetic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what stimulates hyperpolarisation

A

norepinephrine

sympathetics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what acts as a lubricant during chewing

A

mucin which is a glycoprotein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

how is reflex chewing initiated

A

by food in mouth which is relayed from mechanoreceptors to the brain stem initiates a reflex pattern of activity in chewing muscles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what are the 3 phases of swallowing

A

oral phase
pharyngeal phase
oesophageal phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

where is the swallowing centre

A

medulla and lower pons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what innervates the lower oesophagus

A

vagal motor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

describe the swallowing refelex

A
  1. Upper oesophageal sphincter opens to allow bolus of food to enter
    oesophagus
  2. Upper oesophageal sphincter closes
  3. Primary peristaltic contraction mediated by swallowing reflex involves a
    series of coordinated contractions creating a region of high pressure
    behind the bolus (accelerated by gravity)
  4. Lower oesophageal sphincter opens mediated by peptidergic nerves in
    the vagus releasing VIP (vasoactive intestinal peptide)
  5. Receptive relaxation of the orad region of the stomach
  6. Lower oesophageal sphincter closes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what may result from achalasia (absence of relaxation)

A

dysphagia
failure of lower oesophageal sphincter to relax
impaired peristalsis in distal regions

could be caused by Selective loss of neurons which regulate the lower oesophageal sphincter by releasing vasoactive intestinal
peptide (VIP)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what does the parasympathetic NS do

A

stimulate gastric smooth muscle motility and secretions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

what does the sympathetic NS do

A

inhibit motility and secretions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

what myenteric nerves innervate the stomach

A

parasympathetic innervation via the vagus

sympathetic via the coeliac ganglion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

how does the stomach receive sensory innervation

A

sensory receptors and the ENS

and centrally via the vagal and splanchnic nerves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

what can the stomach sense

A

(pressure, distension,

pH, pain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

what layers make up the muscularis externa

A

oblique, circular and longitudinal muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

what is the orad

A

upper proximal part of the stomach which distends in order to make room for food
the stomach can be increased to 1.5 l

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

what afferent information is sent via the vagus

A

Mechanoreceptors associated with chewing, oesophageal
and stomach distension relay information to CNS via
sensory neurons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

what efferent information is sent via the vagus

A

efferent information from the CNS causes orad relaxation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

what neuropeptide is released from postganglionic peptidergic vagal neurons in order to relax the orad

A

vasoactive intestinal peptide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

what part of the stomach is responsible for mixing

A

thick muscular wall of the caudad

– contraction waves begin in the middle of the body, move
distally with increasing strength towards the pylorus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

describe the contraction patterns of the stomach

A
  1. propulsion - bolus is pushed towards the closed pylorus
  2. grinding - the antrum churns the trapped material
  3. retropulsion -bolus is pushed back towards the proximal stomach
    some food may be allowed to exit via the pylorus
48
Q

what is the slow wave frequency of the stomach

A

3-5 per min

49
Q

what factors affect the force of contraction

A

para. stimulation, gastrin and motilin increase AP frequency and force of contraction

50
Q

what are Migrating myoelectric complexes

A

• mediated by motilin – released from endocrine cells in the
upper GI tract
occur every 90 minutes
Clear stomach of residue remaining from previous
meal

51
Q

how long does it take to empty the gastric contents after a meal

A

3 hours

52
Q

what Physical factors affect

emptying

A
  1. Liquids empty more rapidly than solids
  2. Isotonic fluids empty more rapidly than
    hypo- or (especially) hypertonic fluids
  3. Solids must be reduced to particles
53
Q

what is the effect of fat on the GI system

A

cholecystokinin is secreted

54
Q

what is the function of the small intestine

A
  1. Mixes chyme with digestive enzymes and
    pancreatic secretions
  2. Exposes nutrients to the intestinal mucosa
    for absorption
  3. Propels unabsorbed chyme into large
    intestine
55
Q

how many waves are in the duodenum

A

12 per minute

56
Q

how many waves are in the ileum

A

9 per minute

57
Q

what coordinates contraction

A

ENS

58
Q

what causes orad contraction

A

aCh and substance P

59
Q

what causes caudad relaxation

A

VIP and nitric oxide

60
Q

what is the taeniae coli

A

longitudinal muscle concentrated in 3 bands

61
Q

what parts of the colon are innervated by the vagus

A

caecum, ascending colon and transverse colon

62
Q

what parts of the colon are innervated by the pelvic nerves

A

• Descending and sigmoid colon, rectum and anal canal

Stimulation causes expulsive contractions of the distal colon

63
Q

what does the sympathetic ns do to the colon

A

stops colonic movements

64
Q

why might the faeces be retained

A

Na+ and water retention

65
Q

what are the haustra

A

the sac like segments of the colon

66
Q

why would you have hard faeces in constipation

A

more water is absorbed because more time in GI tract

67
Q

what reflexes cause propulsion of faeces into the rectum

A

gastrocolic and duodenocolic reflexes

68
Q

what is the gastro colic reflex

A

Distension of the stomach by food increases the
motility of the colon and the frequency of mass
movements in the large Intestine
Afferent limb in the stomach mediated by the
parasympathetic nervous system.
The efferent limb of the reflex increasing colon
motility is mediated by CCK and gastrin.

69
Q

what is the rectosphincteric reflex

A

As rectum fills with faeces, the smooth muscle of the rectum

contracts and the internal anal sphincter relaxes but the external anal spincter remains closed

70
Q

where is the vomiting centre

A

in the medulla

71
Q

how does vomiting work

A
  • Reverse peristalsis in small intestine
  • Relaxation of the stomach and pylorus
  • Forced inspiration to increase abdominal pressure
  • Relaxation of the lower oesophageal sphincter
  • Forceful expulsion of gastric and duodenal content
72
Q

what afferent information stimulates vomiting

A
  • Vestibular system
  • Back of throat
  • GI tact
  • Chemoreceptor trigger zone in the 4th ventricle
73
Q

what are the main breakdown products of carbohydrate absorption

A

glucose
galactose
fructose

74
Q

how are glucose and galactose absorbed

A

Na dependant cotransport

75
Q

how is fructose absorbed

A

facilitated diffusion

76
Q

what is SGLT1

A 
sodium dependent
glucose transporter 1 located
on the apical membrane
transports glucose and
galactose
77
Q

what is GLUT5

A

glucose transporter 5
transports fructose across the
apical membrane

78
Q

how does protein digestion happen

A

in the stomach with pepsin

then in the small intestine with pancreatic and brush border proteases

79
Q

where is alpha amylase found

A

mouth

80
Q

what is endopeptidase

A

hydrolyses the interior peptide bonds of proteins

81
Q

what is exopeptidase

A

hydrolyses one amino acid at a time from the exterior

82
Q

how are pancreatic proteases secreted in the small intestine

A

as inactive precursors

83
Q

how is trypsinogen activated

A

brush border enzyme enterokinase to the active form trypsin

84
Q

what does trypsin do

A

catalyses the conversion of other inactive precursors to active enzymes

85
Q

how are amino acids absorbed from the small intestine

A

Na dependant co transport

86
Q

how are dipeptides and tripeptides absorbed from the small intestine

A

H+ dipeptide cotransport

87
Q

where does fat digestion begin

A

stomach with the action of lingual and gastric lipases

88
Q

how is fat digestion completed

A

in the small intestine with the action of pancreatic enzymes

89
Q

what is fat digested to

A

glycerol and free fatty acids

90
Q

what is the function of gastric lipase

A

digest fats

slow the rate of gastric emptying so that pancreatic enzymes are able to digest lipid

91
Q

where is cholecystokinin secreted from

A

I cells of the duodenal and jejunal mucosa in response to the presence of monoglycerides and fatty acids and peptides

92
Q

what substances emulsify dietary lipids

A

Bile salts, lysolecithin and products of lipid digestion

93
Q

what does emulsification produce

A

small droplets of lipids
dispersed in an aqueous solution creating a large
surface area for pancreatic enzyme digestion

94
Q

what pancreatic enzymes complete lipid digestion

A

pancreatic lipase, cholesterol

ester hydrolase and phospholipaseA2 and the protein, colipase

95
Q

what are chylomicrons made from

A

fats, cholesterol (inside) and proteins (outside)

96
Q

how do chylomicrons enter the blood

A

lacteals to thoracic duct which empties into the blood stream

97
Q

how are fatty acids absorbed

A

bile salts which form micelles

98
Q

what are Crypts of Lieberkuhn in the small intestine for

A

secretion

99
Q

what are colonic glands for

A

secretion

100
Q

how often are villous cells replaced

A

approx. every 2-3 days

101
Q

where is the majority of water reabsorbed

A

small intestine

102
Q

where is sodium reabsorbed

A

jejunum, ileum and colon

103
Q

what cells in the pancreas produce digestive enzymes

A

basophillic cells

stimulated by CCK

104
Q

what cells in the pancreas produce bicarbonate ions

A

centroacinar cells stimulated by secretin

105
Q

where is the submucosal plexus

A

between the submucosa and the circular muscle layer

106
Q

what is found in the sub mucosa

A 
– Loose	connective tissue	
– Larger	blood vessels	
– Lymphatics
– Secretory glands	
– Enteric	neurones in the submucosa	-submucosal	plexus
107
Q

what is found in the muscularis externa

A

– Inner layer of circular muscle
– Outer layer of longitudinal muscle
– Enteric neurones between the muscle layers – myenteric plexus

108
Q

what is found in the serosa

A

outer layer of connective tissue and squamous epithelia

109
Q

what is the extrinsic autonomic NS

A

sympathetic and parasympathetic

110
Q

what is the intrinsic component of the ANS

A

enteric NS
Meissner’s plexus (submucosal)
and Auerbach’s plexus- myenteric

111
Q

describe the organisation of the somatic NS

A

single motorneurone
no ganglia
ACh

112
Q

describe the sympathetic organisation

A

have ganglia close to the spinal cord which secrete ACh
have long
postganglionic neurones
thoracolumbar (ps is craniosacral)

norepinephrine is secreted postganglion

113
Q

what are the 3 plexuses in the sympathetic GI supply

A

coeliac plexus
sup mesenteric
inferior mesenteric

114
Q

what reflexes are controlled by the ENS

A

secretion, peristalsis, mixing, inhibition

115
Q

what reflexes travel from the GI tract to the prevertebral sympathetic ganglia and then back to the GI tract

A

reflexes that transmit signals to other areas of the stomach
gastrocolic, enterogastric, colonoilial

116
Q

what reflexes travel from the GI tract to the brain stem or spinal cord

A

reflexes controlling motility and secretion

pain reflexes which inhibits the GI tract

defecation which produces reflex contractions

117
Q

what is catarrh

A

a build up of mucus in a body cavity

results from inflammation of the mucus membrane

MD3002 (56 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions