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60 > L29 - Control of GI tract motility > Flashcards

L29 - Control of GI tract motility Flashcards

1
Q

list main functions of GI tract

A
  1. digestion
  2. absorption of nutrients&electrolytes
  3. water absorption
  4. immune function
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2
Q

in what layer of the GI tract do absorbed nutrients enter blood / lymph

A

submucosa

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3
Q

the enteric nervous system is composed of what nerve plexuses

A

submucosal nerve plexus

myenteric nerve plexus

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4
Q

what is the extrinsic control of motility

A

ANS

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5
Q

what is the intrinsic control of motility

A

enteric nervous system (myenteric and submucosal nerve plexus’s)

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6
Q

what is the long reflex for motility control

A
  1. receptors in GI detect stimuli in lumen
  2. send signal to CNC
  3. CNS sends signal to enteric nervous system
  4. effect (on SM / gland)
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7
Q

what is the short reflex for motility control

A

receptors in GI detect stimuli and send signal straight to enteric nerve plexus’s

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8
Q

what are the 3 main contractions that occur in GI tract

A

peristalsis
segmentation
pendular contractions

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9
Q

what is peristalsis

A

rhythmic contractions of circular and longitudinal muscle

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10
Q

what is segmentation

A

powerful contraction of circular muscle to break up food

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11
Q

what is pendular contractions

A

powerful contractions of longitudinal muscle

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12
Q

what receptors mediate deglutition and where are they located

A

mechanoreceptors in pharynx

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13
Q

where is the swallowing centre located

A

medulla oblogata

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14
Q

describe deglutition process

A
  1. food at back of pharynx stimulates mechanoreceptors which sends signal to swallowing centre which initiates swallowing reflex
    2.
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15
Q

the swallowing centre sends efferent impulses via what pathways

A

vagus nerve

glossopharyngeal nerve

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16
Q

describe process of swallowing reflex

A

(involuntary pharangeal phase)

  1. soft palate elevates preventing food entering nasal passages
  2. epiglottis covers glottis preventing food into lungs
  3. respiration ceases
  4. upper oesophageal sphincter relaxes
  5. pharynx strongly contracts
  6. initiates involuntary oesophageal phase
  7. peristaltic wave moves food to stomach
  8. lower oesophageal sphincter relaxed so food can enter stomach, then it closes
17
Q

what initiates peristaltic contractions (in stomach)

A

pacemaker cells in longitudinal layer

18
Q

what happens to the peristaltic wave in the regions of stomach

A

produces only a ripple to antrum, where it produces a more powerful contraction mixing food

19
Q

describe the basal electrical rhythm of stomach

A

slow depolarisation-repolarisation waves in longitudinal muscle (that induce circular muscle through gap junctions) - don’t always produce contraction

20
Q

what factors increase frequency and force of peristaltic contractions

A

PNS
Gastrin
motilin

21
Q

what factors decrease frequency and force of peristaltic contractions

A

SNS

secretin

22
Q

name two enterogastrones

A

secretin

CCK

23
Q

what stimulates secretin

A

acid in duodenum

24
Q

what stimulates CCK

A

AA and FAs in SI

25
Q

what stimulates gastrin

A

PNS

peptides/AA in stomach

26
Q

what inhibits gastrin

A

stomach acid and somatostatin

27
Q

what is the function of motilin

A

induces migrating myoelectric complex (MMC)

28
Q

what is the migrating myoelectric complex and what is its function

A

peristaltic waves that spread through SI and consecutively start further along until large intestine

empties stomach and SI of remaining chyme

29
Q

what is the intrinsic control of gastric emptying

A

short reflexes due to duodenum distension

30
Q

what inhibits gastric emptying

A

SNS
CCK
Secretin

31
Q

what promotes gastric emptying

A

PNS

60 (27 decks)

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