Physiology and pharmacology

Question 1

what additional layer of muscle is present in the stomach

Answer 1

oblique

Question 2

what does circular muscle contraction do to the lumen

Answer 2

narrower and longer

Question 3

what does contract of the longitudinal muscle do to the lumen

Answer 3

intestine becomes shorter and fatter

Question 4

how does contraction and depolarization take place in the GI tract

Answer 4

• 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

Question 5

what is slow wave electrical activity driven by

Answer 5

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

Question 6

what is upstroke mediated by

Answer 6

voltage activated calcium channels

Question 7

where are interstitial cells of cajal located

Answer 7

between the longitudinal and circular muscle layers in the submucosa

Question 8

what is downstroke mediated by

Answer 8

voltage activated K+ cells

Question 9

do all slow waves trigger contraction

Answer 9

no threshold for action potential must be reached

Question 10

what does depolarization of smooth muscles do

Answer 10

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

Question 11

what does the Myenteric (Auerbach’s) plexus do

Answer 11

regulates motility and sphincters

Question 12

what does submucous (Meisserner’s) plexus do

Answer 12

mainly modulates epithelia and blood vessels

Question 13

is the ENS intrinsic or extrinsic to GI tissue

Answer 13

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

Question 14

what do all preganglionic fibres release

Answer 14

acetylcholine

Question 15

what do postganglionic fibres in sympathetic nervous system release

Answer 15

noradrenaline

Question 16

what does parasympathetic innervation of GI tract do

Answer 16

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

Question 17

what does innervation of the parasympathetic nervous system do

Answer 17

• increase sphincter tone

- decreased motility, secretion and blood flow

Question 18

what is another name for intrinsic reflex

Answer 18

local

Question 19

what do local/intrinsic nerve reflexes do

Answer 19

cause peristalsis

Question 20

what does the short reflex do

Answer 20

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

Question 21

what does the long reflex do

Answer 21

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

Question 22

what triggers peristalsis

Answer 22

distension of the gut wall

Question 23

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

Answer 23

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

Question 24

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

Answer 24

acetylcholine and substance P

Question 25

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

Answer 25

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)

Question 26

what is segmentation

Answer 26

mixing, churning movements | rhythmic contractions of the circular muscle layer that mix and divide luminal contents

Question 27

where does segmentation occur

Answer 27

in the small and large intestine

Question 28

what is segmentation in the large intestine called

Answer 28

haustration

Question 29

what is colonic mass movement

Answer 29

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

Question 30

what is migrating motor complex

Answer 30

powerful sweeping contraction from stomach to terminal ileum

Question 31

what are tonic contractions

Answer 31

sustained contractions

Question 32

which organs have low pressure tonic contractions

Answer 32

organs with a major storage function eg stomach

Question 33

where are high pressure contractions take place

Answer 33

sphincters

Question 34

how many sphincters in the GI tract are there

Answer 34

6

Question 35

what type of muscle is the upper oesophageal sphincter made of

Answer 35

skeletal muscle

Question 36

if food become lodged in the oesophagus what is stimulated

Answer 36

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

Question 37

what is luminal digestion

Answer 37

digestion mediated by pancreatic enzymes secreted into the duodenum

Question 38

give some examples of oligosaccharides

Answer 38

lactose and sucrose

Question 39

what is membrane digestion

Answer 39

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

Question 40

what makes up starch

Answer 40

amylose and amylopectin

Question 41

what is branched amylose or amylopectin

Answer 41

amylopectin

Question 42

what type of enzyme is alpha amylase

Answer 42

an endoenzyme

Question 43

what does a amylase break down

Answer 43

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

Question 44

can a amylase produce glucose

Answer 44

no

Question 45

what can a amylase not break down

Answer 45

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

Question 46

what are oligosaccharidases

Answer 46

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

Question 47

what are the substrates of lactase

Answer 47

glucose and galactose

Question 48

what are the substrates of sucrase

Answer 48

glucose and fructose

Question 49

what is unique about isomaltase

Answer 49

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

Question 50

where does absorption of glucose, galactose and fructose occur

Answer 50

the duodenum and jejunum

Question 51

what are glucose and galactose absorbed (specifically)

Answer 51

secondary active transport mediated by SGLTI

Question 52

what is fructose absorbed by and how

Answer 52

fructose is absorbed by facilitated diffusion mediated by GLUT5

Question 53

how is exit for all monosaccharides mediated

Answer 53

facilitated diffusion by GLUT2

Question 54

what are enterocytes

Answer 54

tall columnar cells with a brush border

Question 55

what are goblet cells

Answer 55

produce mucin to protect epithelium and lubricate passage of material

Question 56

what are paneth cells

Answer 56

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

Question 57

what is contained within the muscularis externa of the stomach

Answer 57

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

Question 58

what happens in the transition from stomach mucosa to duodenal mucosa

Answer 58

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

Question 59

what project downwards inbetween the villi

Answer 59

crypts of Lieberkuhn

Question 60

what doe the small intestine contain within its layers

Answer 60

Brunner's glands in the submucosa

Question 61

what does the jejunum distinctively have

Answer 61

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

Question 62

what does the ileum distinctivey have in it layers

Answer 62

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

Question 63

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

Answer 63

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

Question 64

what are the plicae circualaris

Answer 64

folds with finger like projections: the villi

Question 65

where do the plicae circualris form from

Answer 65

mucosa and submucosa

Question 66

which tissue type is present in large quanitites in the ileum

Answer 66

lymphoid

Question 67

what are large aggregations of lymphoid tissue in the ileum called

Answer 67

Peyer's patches

Question 68

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

Answer 68

absorptive cells: for removal of salts and thereby water | goblet cells: for the secretion of mucus to lubricate the colon

Question 69

how are the cells arranged in the large intestine

Answer 69

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

Question 70

how is the longitudinal muscle in the large intestine distinct

Answer 70

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

Question 71

what is the appendix

Answer 71

a blind ending hollow extension of the ceacum

Question 72

what is the tissue like in the appendix

Answer 72

less crypts than the rest of the colon | circular arrangement of lymphoid tissue in the submucosa and often the lamina propria

Question 73

what is the tissue in the anal canal like

Answer 73

stratified squamous epithelium

Question 74

where does the ENS receive its input from

Answer 74

autonomic nervous system

Question 75

what are the two parts of the ENS called

Answer 75

myenteric plexus and submucosa plexus

Question 76

what does the submucosa plexus do

Answer 76

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

Question 77

all carbohydrates must be converted to what for absorption

Answer 77

monosaccharides

Question 78

what type of enzyme is amylase

Answer 78

an endoenzyme

Question 79

which oligosaccharidase only has one substrate

Answer 79

lactase- breaks down lactose to glucose and galactose

Question 80

how are glucose and galactose absorbed

Answer 80

by secondary active transport mediated by SGLT1

Question 81

how is glucose absorbed

Answer 81

by facilitated diffusion mediated by GLUT5

Question 82

how is exit for all monosacchardies mediated

Answer 82

by GLUT2

Question 83

what are the four ways that a protein can be digested

Answer 83

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

Question 84

what type of enzyme is pepsin

Answer 84

an endopeptidase

Question 85

how many pancreatic proteases are present in the duodenum

Answer 85

5

Question 86

what are the pancreatic enzymes found in the duodenum called

Answer 86

trypsin, chymotrypsin, elastase, carbopeptidase A and carbopeptidase B