GI 1 - intro

Question 1

what are 4 roles of the GI tract

Answer 1

digestion, absorption, elimination, endocrine

Question 2

what does the GI eliminate and how

Answer 2

waste and toxins with defacation and vomiting

Question 3

what are 4 main endocrine hormones in GI

Answer 3

5-HT, gastrin, ghrelin, cholecystokinin

Question 4

what does the GI absorb and digest

Answer 4

nutrients and orally available drugs

Question 5

what 2 main parts are in the digestive system

Answer 5

the digestive tract (hollow organ) and the organs of digestion

Question 6

what are the 4 main things in the digestive tract (not accessory organs)

Answer 6

mouth, esophagus, stomach, intestines

Question 7

what are the 5 main accessory organs in the digestive tract / organs of digestion

Answer 7

tongue, salivary glands, pancreas, gallbladder, liver

Question 8

what are the 2 main muscle types in the GI tract

Answer 8

circular and longitudinal muscles

Question 9

what do the circular and longitudinal muscles do

Answer 9

transport and mix food for digestion

Question 10

what layer of the GI tract is the outermost / where food is exposed

Answer 10

the mucosa

Question 11

what are the 2 nerve plexus in the GI tract

Answer 11

submucosal and myenteric plexus

Question 12

where is the mucosa

Answer 12

outer most layer (exposed to food)

Question 13

what kind of neural network is the enteric nervous system

Answer 13

intrinsic

Question 14

what are 4 things the enteric nervous system regulates

Answer 14

motility, secretion, blood flow, immune response

Question 15

what is the enteric nervous system integrated with

Answer 15

the autonomic nervous system

Question 16

can the enteric nervous system act independently with the CNS

Answer 16

yes

Question 17

what does the submucosal plexus innervate

Answer 17

epithelia and muscle cells

Question 18

what does the myenteric plexus do

Answer 18

regulates gut motility and secretion

Question 19

where is the myenteric plexus

Answer 19

between muscle layers

Question 20

which fibres does the enteric nervous system receive (sym or para)

Answer 20

both
para- vagus nerve
sympathetic too

Question 21

what are 4 roles of vagal para fibres in the ENS

Answer 21

excitatory, increases gut motility, dilate sphincters (facilitate transit), increases secretions (ACh)

Question 22

what are 2 roles of sympathetic fibres in the ENS

Answer 22

decrease gut motility, constrict sphincters (slow down digestion, more chance to absorb)

Question 23

what do the sensory nerves in the ENS sense

Answer 23

mechanical and chemical stimuli

Question 24

what are 3 pathways after the ENS detects mechanical and chemical stimuli

Answer 24

• spinal and brainstem reflexes regulate digestive function
• input to central autonomic circuits that regulate feeding and illness behaviours
• transmit painful and non painful sensations

Question 25

what is peristalsis

Answer 25

food moving from mouth to anus

Question 26

why is segmentation helpful

Answer 26

mixing food to facilitate digestion, more surface area of food for acid and enzymes to act on

Question 27

what are the 3 main forms of gut motility

Answer 27

peristalsis and segmentation and isolated contraction

Question 28

what main 2 things determine gut motility

Answer 28

smooth muscle properties and chemical inputs

Question 29

what 3 types of chemical inputs can effect gut motility

Answer 29

nerves, hormones, paracrine signals

Question 30

do all regions in the GI have the same type of motility (explain)

Answer 30

no, like tonic contractions in sphincters and phasic contractions in small intestine and colon

Question 31

what drives phasic activity in SI motility

Answer 31

slow waves

Question 32

what causes contractions in the SI to cause motility

Answer 32

rhythmic electrical activity

Question 33

what happens to wave propagation with more distal segments

Answer 33

it slows down

Question 34

what happens once a slow wave reaches threshold (4)

Answer 34

VGCC open, Ca++ enters, APs fire, muscles contract

Question 35

what is isolated contraction

Answer 35

when the contents move both orally and aborally

Question 36

what is segmentation

Answer 36

mixes contents over short length of intestine

Question 37

what is peristalsis

Answer 37

propelling contents aborally (going down towards anus)

Question 38

what causes peristalsis

Answer 38

contraction and relaxation

Question 39

what causes segmentation and peristalsis

Answer 39

longitudinal and circular muscle coordinated movement

Question 40

how do the muscles work to make peristalsis

Answer 40

contraction wave in ring muscle, moving aborally behind an aboral relaxation wave

Question 41

how do the muscles work to make segmentation

Answer 41

alternating ring contraction to help mix contents

Question 42

what triggers the peristaltic reflex

Answer 42

mechanical stretch and mucosal stimulation

Question 43

what does the peristaltic relax activate (2)

Answer 43

excitatory motorneurons above bolus and inhibitor motor neurons below (relax)

Question 44

how do the excitatory motorneurons above bolus in the peristaltic reflex work

Answer 44

they release 5HT from enterochromaffin cells

Question 45

what do enterochromaffin cells release in the peristaltic reflex

Answer 45

5HT

Question 46

what cells release 5HT in the peristaltic reflex

Answer 46

enterochromaffin cells

Question 47

what happens when you activate inhibitor motor neurons below the bolus (peristaltic reflex)

Answer 47

relaxes gut wall below bolus

Question 48

what are 5 hormones released from the gut

Answer 48

- gastrin - 5-HT - motilin - cholesystokinin (CCK) - glucagon-like peptide 1 (GLP-1)

Question 49

where is gastrin made

Answer 49

in mucosal enteroendrocrine cells

Question 50

what does gastrin do

Answer 50

stimulate acid secretion by parietal cells in stomach

Question 51

what cells are affected by gastrin

Answer 51

parietal

Question 52

which hormone stimulate acid secretion by parietal cells in stomach

Answer 52

gastrin

Question 53

where is 5HT made

Answer 53

enterochromaffin cells

Question 54

what do enterochromaffin cells release

Answer 54

5HT

Question 55

where is motilin made

Answer 55

mucosal cells

Question 56

what does 5HT from enterochromaffin cells do

Answer 56

release of ACh from nerves in ENS

Question 57

what hormone do mucosal cells make

Answer 57

motilin

Question 58

what does motilin do

Answer 58

stimulates GI smooth muscle contraction

Question 59

where is CCK released from

Answer 59

small intestine enteroendocrine cells

Question 60

what does CCK stimulate

Answer 60

pancreatic enzyme secretion

Question 61

which enzyme stimulates pancreatic enzyme secretion

Answer 61

CCK

Question 62

which enzyme is released from small intestine enteroendocrine cells

Answer 62

CCK

Question 63

what 3 things does glucagon-like peptide (GLP-1) do

Answer 63

stimulates insulin release, inhibits glucagon release, promotes satiety

Question 64

what are 2 things that enteroendrocrine cells respond to (local signals to release hromones)

Answer 64

nutrients and neurotransmitters