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GI > Physiology and pharmacology > Flashcards

Physiology and pharmacology Flashcards

1
Q

what additional layer of muscle is present in the stomach

A

oblique

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2
Q

what does circular muscle contraction do to the lumen

A

narrower and longer

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3
Q

what does contract of the longitudinal muscle do to the lumen

A

intestine becomes shorter and fatter

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4
Q

how does contraction and depolarization take place in the GI tract

A
  • gap junctions allow spread of electrical current from cell to cell forming a functional syncytium
  • hundreds of cells are depolarized and contract at the same time as a synchronous wave
  • slow waves, rhythmical patterns of membrane depolarization and repolarization that spreads from cell to cell via gap junctions
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5
Q

what is slow wave electrical activity driven by

A

interstitial cells of Cajal-pacemaker cells interspersed between the smooth muscle cells

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6
Q

what is upstroke mediated by

A

voltage activated calcium channels

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7
Q

where are interstitial cells of cajal located

A

between the longitudinal and circular muscle layers in the submucosa

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8
Q

what is downstroke mediated by

A

voltage activated K+ cells

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9
Q

do all slow waves trigger contraction

A

no threshold for action potential must be reached

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10
Q

what does depolarization of smooth muscles do

A

bring the slow wave peak to threshold for opening of L-type voltage-activated Ca2+ channels

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11
Q

what does the Myenteric (Auerbach’s) plexus do

A

regulates motility and sphincters

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12
Q

what does submucous (Meisserner’s) plexus do

A

mainly modulates epithelia and blood vessels

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13
Q

is the ENS intrinsic or extrinsic to GI tissue

A

intrinsic it forms a complete reflex circuit that can operate independently but hormones and extrinsic nerves exert a strong regulatory influence

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14
Q

what do all preganglionic fibres release

A

acetylcholine

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15
Q

what do postganglionic fibres in sympathetic nervous system release

A

noradrenaline

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16
Q

what does parasympathetic innervation of GI tract do

A
  • increase gastric, pancreatic and small intestine secretions, blood flow and smooth muscle contraction
  • relax some sphincters, receptive relaxation of stomach
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17
Q

what does innervation of the parasympathetic nervous system do

A
  • increase sphincter tone

- decreased motility, secretion and blood flow

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18
Q

what is another name for intrinsic reflex

A

local

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19
Q

what do local/intrinsic nerve reflexes do

A

cause peristalsis

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20
Q

what does the short reflex do

A

intestine-intestinal inhibitory reflex (local distension activates sensory neurone exciting sympathetic pre-ganglionic fibres that cause inhibition of muscle activity in adjacent areas

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21
Q

what does the long reflex do

A

gastroileal reflex (increase in gastric activity causes increased propulsive activity in the terminal ileum

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22
Q

what triggers peristalsis

A

distension of the gut wall

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23
Q

what happens in in the oral direction in peristalsis following altered activity of interneurones

A

altered activity of motorneurones
circular muscle contracts (release of ach and substance P)
longitudinal muscle relxes (release of VIP and NO from inhibitory motorneurone)

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24
Q

which 2 substances in the GI tract cause contraction of muscle in peristalsis

A

acetylcholine and substance P

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25
Q

what happens in the aboral direction in peristalsis following the altered activity of interneurones

A

altered activity of motor neurones
longitudinal muscle contracts (release of ACh and substance P from excitory motorneurone)
circular musces relaxes relese of VIP and NO from inhibitory motorneurone)

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26
Q

what is segmentation

A

mixing, churning movements

rhythmic contractions of the circular muscle layer that mix and divide luminal contents

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27
Q

where does segmentation occur

A

in the small and large intestine

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28
Q

what is segmentation in the large intestine called

A

haustration

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29
Q

what is colonic mass movement

A

powerful sweeping contraction that forces faeces into the rectum-occurs a few times a day

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30
Q

what is migrating motor complex

A

powerful sweeping contraction from stomach to terminal ileum

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31
Q

what are tonic contractions

A

sustained contractions

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32
Q

which organs have low pressure tonic contractions

A

organs with a major storage function eg stomach

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33
Q

where are high pressure contractions take place

A

sphincters

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34
Q

how many sphincters in the GI tract are there

A

6

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35
Q

what type of muscle is the upper oesophageal sphincter made of

A

skeletal muscle

36
Q

if food become lodged in the oesophagus what is stimulated

A

a secondary peristaltic wave-more forceful than primary-locally triggered
increased saliva production

37
Q

what is luminal digestion

A

digestion mediated by pancreatic enzymes secreted into the duodenum

38
Q

give some examples of oligosaccharides

A

lactose and sucrose

39
Q

what is membrane digestion

A

digestion mediated by enzymes situated at the brush border of epithelial cells

40
Q

what makes up starch

A

amylose and amylopectin

41
Q

what is branched amylose or amylopectin

A

amylopectin

42
Q

what type of enzyme is alpha amylase

A

an endoenzyme

43
Q

what does a amylase break down

A

linear internal a-1,4 linkages but not terminal a-1,4 linkages

44
Q

can a amylase produce glucose

A

no

45
Q

what can a amylase not break down

A

terminal a-1,4 linkages

a-1,6 linkages at branch points or a 1,4 linkages adjacent to branch points

46
Q

what are oligosaccharidases

A

integral membrane proteins with a catalytic domain that face the lumen of the GI tract

47
Q

what are the substrates of lactase

A

glucose and galactose

48
Q

what are the substrates of sucrase

A

glucose and fructose

49
Q

what is unique about isomaltase

A

it is the only enzyme that can split the branching a-1,6 linkages of a-limit dextrins

50
Q

where does absorption of glucose, galactose and fructose occur

A

the duodenum and jejunum

51
Q

what are glucose and galactose absorbed (specifically)

A

secondary active transport mediated by SGLTI

52
Q

what is fructose absorbed by and how

A

fructose is absorbed by facilitated diffusion mediated by GLUT5

53
Q

how is exit for all monosaccharides mediated

A

facilitated diffusion by GLUT2

54
Q

what are enterocytes

A

tall columnar cells with a brush border

55
Q

what are goblet cells

A

produce mucin to protect epithelium and lubricate passage of material

56
Q

what are paneth cells

A

cells found at the base of the crypts of Lieberkuhn they have a defensive function and have a role in regulation of bacterial flora

57
Q

what is contained within the muscularis externa of the stomach

A

an additional layer of muscle the oblique layer which helps with churrning. It is located internal to the circular layer

58
Q

what happens in the transition from stomach mucosa to duodenal mucosa

A

the inner circular layer of smooth muscle is markedly thickened to form the pyloric sphincter

59
Q

what project downwards inbetween the villi

A

crypts of Lieberkuhn

60
Q

what doe the small intestine contain within its layers

A

Brunner’s glands in the submucosa

61
Q

what does the jejunum distinctively have

A

tallest villi, located on permanent circular folds of the mucosa and submucosa, the plicae circularis

62
Q

what does the ileum distinctivey have in it layers

A

lymphoid follicles called Peyer’s patches found in the submucosa and often extending into the lamina propria

63
Q

where are the Brunner’s glands found and what do they do

A

when stimulated by the presence of chime they produce a thin, alkaline mucous to neutralise the chyme

64
Q

what are the plicae circualaris

A

folds with finger like projections: the villi

65
Q

where do the plicae circualris form from

A

mucosa and submucosa

66
Q

which tissue type is present in large quanitites in the ileum

A

lymphoid

67
Q

what are large aggregations of lymphoid tissue in the ileum called

A

Peyer’s patches

68
Q

what are the two main types of cells found in the large intestine

A

absorptive cells: for removal of salts and thereby water

goblet cells: for the secretion of mucus to lubricate the colon

69
Q

how are the cells arranged in the large intestine

A

in straight, tubular glands called crypts that extend down into the muscularis mucosa

70
Q

how is the longitudinal muscle in the large intestine distinct

A

it is not continuous but is found in 3 muscular strips TENIAE COLI

71
Q

what is the appendix

A

a blind ending hollow extension of the ceacum

72
Q

what is the tissue like in the appendix

A

less crypts than the rest of the colon

circular arrangement of lymphoid tissue in the submucosa and often the lamina propria

73
Q

what is the tissue in the anal canal like

A

stratified squamous epithelium

74
Q

where does the ENS receive its input from

A

autonomic nervous system

75
Q

what are the two parts of the ENS called

A

myenteric plexus and submucosa plexus

76
Q

what does the submucosa plexus do

A

control the muscle of the muscularis mucosae and help regulate secretion in the epithelium

77
Q

all carbohydrates must be converted to what for absorption

A

monosaccharides

78
Q

what type of enzyme is amylase

A

an endoenzyme

79
Q

which oligosaccharidase only has one substrate

A

lactase- breaks down lactose to glucose and galactose

80
Q

how are glucose and galactose absorbed

A

by secondary active transport mediated by SGLT1

81
Q

how is glucose absorbed

A

by facilitated diffusion mediated by GLUT5

82
Q

how is exit for all monosacchardies mediated

A

by GLUT2

83
Q

what are the four ways that a protein can be digested

A

by luminal enzymes, by enzymes on the brush border, by intracellular hydrolysis or the peptide is transported out of the enterocyte without intervening intracellular hydrolysis

84
Q

what type of enzyme is pepsin

A

an endopeptidase

85
Q

how many pancreatic proteases are present in the duodenum

A

5

86
Q

what are the pancreatic enzymes found in the duodenum called

A

trypsin, chymotrypsin, elastase, carbopeptidase A and carbopeptidase B

GI (13 decks)

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