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HUBS192 > GI PHYSIOLOGY I - INTRODUCTION AND MOTILITY > Flashcards

GI PHYSIOLOGY I - INTRODUCTION AND MOTILITY Flashcards

1
Q

what is the function of the GI tract?

A

obtain nutrients and replace fluid and salt

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2
Q

TRUE/FALSE: the enteric nervous system can act independently of the central and autonomic nervous system

A

True

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3
Q

what are the basic principles needed for regulation of the GI system to serve its function?

A
  • conditions in intestinal lumen are regulated
  • there are receptors in the wall of GI tract to respond to: stretch, change in composition, pH, osmolarity, amino acids, sugars, fats
  • smooth muscles and glands being effectors: these reflex according to receptors stimulation - e.g. smooth muscle contraction and gland secretion
  • there are nervous and hormonal regulation of GI function
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4
Q

what is central nervous system pathway like?

A
  • co-ordinates activity over long distances
  • modulates activity of enteric nervous system BUT no direct innervation
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5
Q

what stimulates the motility and secretion?

A

parasympathetic nervous system of CNS

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6
Q

what inhibits motility and secretion?

A

sympathetic nervous system of CNS

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7
Q

what regulates the secretion and motility in the enteric nervous system?

A
  • submucosal plexus regulates secretion
  • myenteric plexus regulates motility
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8
Q

what is ENS like?

A
  • involved in local reflex
  • totally self contained
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9
Q

simply describe the pathway of the CNS work on the GI physiology

A
  • external stimuli: see, smell, emotional state, etc.
  • CNS integrate the external stimuli
  • 2 reflexes of the CNS involves parasympathetic and sympathetic
  • parasympathetic when rest and digest, stimulate GI function (secretion and motility) using acetylecholine
  • sympathetic inhibit the GI function
  • enteric nervous system included and act as ‘middleman’ betwwen CNS and GIT
  • long reflex path sends internal stimuli to CNS so it can generates a respond to that internal stimuli
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10
Q

describe the pathway of how Enteric Nervous System acts on GIT?

A
  • GI lumen contents act as internal stimuli
  • the receptors detect conditions in the GI tract (conditions such as the stretchiness and chemical composition within)
  • ENS respond via short LOCAL reflex pathways through: myenteric plexus or submucosal plexus
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11
Q

TRUE/FALSE: GI tract is the largest endocrine organ of the body

A

true

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12
Q

define paracrine

A

signalling that acts directly on next door cells, unlike endocrine which needs to be signal via bloodstream

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13
Q

what do sensor cells also be called?

A

enteroendocrine cells

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14
Q

describe the enteroendoccrine cells of the GIT?

A
  • epithelial cells
  • detect luminal content and release hormone
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15
Q

what are the 4 critical GI hormones?

A
  • gastrin
  • gastric inhibitory peptide (GIP)
  • secretin
  • cholescytokinin (CCK)
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16
Q

what are the 2 types of GI motility?

A
  • tonic: sustained and long
  • phasic: waves of contraction and relaxation in a short period of time
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17
Q

what is the pattern that is a combination of 2 or more simpler patterns

A

retropulsion

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18
Q

TRUE/FASLE: relaxation sometimes can be a motility patter such as storage in the stomach

A

true

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19
Q

what type of muscle supports GI motility?

A

smooth muscle

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20
Q

what are the properties of the smooth muscle that assist the GI motility?

A
  • spontaneously active
  • contracts without external input
  • contains pacemaker cells
  • strength of contraction regulated by nervous and hormonal input
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21
Q

list the frequency of contraction of each GI region

A
  • stomach: 3 per min
  • duodenum: 12 per min
  • ileum: 9 per min
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22
Q

what are the 2 broad types of motility patterns that are not tonic or phasic

A
  • fasting (migrating motor complex)
  • feeding
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23
Q

describe the characteristic of fasting?

A
  • 4 hours after a meal
  • repeats every 2h until eat
  • housekeeping
  • repeating pattern that helps clear undigested material and helps epithelial cells turnover
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24
Q

what happens during feeding (eating)?

A
  • storage
  • propulsion/movement
  • mixing
25
Q

where does storage happen?

A

stomach and colon

26
Q

where does propulsion and movement happen?

A

esophagus, stomach, small and large intestine

27
Q

where does mixing happen?

A

stomach, small and large intestin

28
Q

what happens to the muscles in order to support storage?

A

relaxation of smooth muscles –> increase volume without change in pressure

29
Q

what type of movement majorily happens along the tube?

A

peristalsis

30
Q

what kind of mixing happening in stomach, small and large intestine?

A
  • stomach: retropulsion
  • small and large intestine: segmentation
31
Q

this is a reminder to review peristalsis and segmentation from lecture 24

A
32
Q

what does chewing do?

A
  • reduce size of food, allows ingestion
  • mixes food with saliva
  • taste
33
Q

chewing is a ______1______ activity with ______2______ muscle, which has _____3______ control of ______4______, _____5_____/ _______6_______

A

1: voluntary
2: skeletal
3: reflex
4: strength
5: frequency
6: rhythm

34
Q

describe swallowing

A
  • rapid transfer of material from mouth to stomach
  • initiated at will, proceeds reflexively
35
Q

which part of stomach responsible for:
1: storage?
2: mechanical digestion?
3: mixing?
4: controlled delivery to duodenum?

A

1: fundus and body of stomach
2: antrum
3: antrum
4: pyloric sphincter

36
Q

during fasting, how much did stomach shrink into?

A

approximately 50mL in volume

37
Q

what does migrating motor complex in stomach means?

A
  • occurs 4h after a meal
  • continues until eat with 2h of inactivity
  • 50min of uncoordinated activity
  • 10min of coordinated activity
38
Q

what does ‘housekeeping’ function of stomach mean?

A
  • removes residual secretions
  • removes undigested material
  • promotes epithelial cell turnover
39
Q

which nerve controls/regulates the receptive relaxation and gastric accommodation of stomach during storage phase of feeding?

A

vagus nerve

40
Q

how does stomach increase volume but not change the pressure?

A

relax the rugae

41
Q

what type of propulsion/movement happens in stomach?

A

peristalsis

42
Q

describe the peristalsis pathway of the stomach

A
  • initiated on greater curvature and spreads to antrum
  • 3 contractions per min
  • first 60 mins following meal gentle
  • 60-300 min more intense activity
43
Q

what assist the super strong squeeze of the stomach

A

an extra third layer of muscle

44
Q

what is retropulsion during mixing and mechanical breakdown of the feeding stage of the stomach?

A

combination of peristalsis and closure of the pyloric sphincter

45
Q

what is the event happen during gastric emptying

A

combination of peristalsis and periodic opening (relaxation of the pyloric sphincter)

46
Q

what regulates the gastric emptying?

A

feedback from duodenum

47
Q

TRUE/FALSE: the rate of gastric emptying is completely independent from the digestive capacity of intestines

A

false

48
Q

what factors affect the gastric emptying?

A
  • size of meal: larger the size, faster the emptying
  • composition of meal
49
Q

what speeds up the gastric emptying?

A
  • larger meal
  • fluid (faster than solids)
50
Q

what slows down the gastric emptying?

A
  • fats
  • acids
51
Q

why does fluid helps speed up the gastric emptying?

A

reduction in size of food particles –> increase in surface area of food –> fasting digestion

52
Q

why do fats and acids slows down the process of gastric emptying?

A
  • fats: difficult to digest and need support of bile salt
  • acids: need to neutralise
53
Q

what is the function of small intestine motility?

A
  • mixing with secretions from pancreas, liver and SI
  • controlled movement/propulsion
  • exposure of products of digestion to absorptive surfaces
54
Q

what is the motility pattern between meals in small intestine?

A

migrating motor complex

55
Q

what is the motility pattern after meals in small intestine?

A

segmentation and some peristalsis

56
Q

what is a special characteristic of large intestinal motility

A
  • large period of inactivity BUT mass movement: 1-2 times/day following meals
57
Q

what type of motility appears in colon?

A

segmentation and peristaltic wave

58
Q

what does segmentation and peristaltic wave do in colon?

A
  • segmentation: exposure to absorptive surface for water and salt absorption
  • peristaltic wave: drives faeces into rectum to initiate defecation
59
Q

the mixing of stomach contents is facilitated by the process of?

A

retropulsion

HUBS192 (23 decks)

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