motility of the gut Flashcards

1
Q

is GI muscle single or multi unit smooth muscle ?

A

coupling of cells to act as single unit

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2
Q

what mechanism operates in smooth muscle to reduce the use of ATP

A

the latch bridge mechanism

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3
Q

are actin + myosin arrangements highly structured in smooth muscle

A

no they arent arranged in rows

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4
Q

which cells act as pacemakers in GI tract ?

A

interstitial cells of Cajal

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5
Q

what is the term used to describe smooth muscle when it is able to function over a wide range of lengths

A

plasticity

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6
Q
what effects do the following have on gastric motility ?
vagal stimulation 
CCK
GIP 
Secretin
A

increase
decrease
decrease
decrease

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7
Q
which has the fastest rate of spontaneous activity 
stomach 
duodenum 
ileum 
colon
A

duodenum - 13 contractions per minute

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8
Q

what are the functions of motility in the GI tract

A

mixing

propulsion

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9
Q

what is motility dependent on ?

A

smooth muscle
enteric nervous system
autonomic nervous system
hormones

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10
Q

describe the contractile activity of the visceral smooth muscle of Gi tract :

A

shows rhythmic cycles of activity through pacemaker cells ( interstitial cells of cajal)

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11
Q

describe the contractile activity of peristalsis

A

waves that move bolus

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12
Q

describe the contractile activity of segmentation

A

churn + fragment bolus

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13
Q

what are 3 main factors influencing GI tract motility ?

A
  • smooth muscle functional syncytium
  • neural control
  • hormonal control
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14
Q

what is smooth muscle functional syncytium ?

A

electrical activity of muscle cells
slow wave of pacemaker potentials
spike potentials that result in contraction

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15
Q

how does neural control influence GI tract motility ?

A

parasympathetic pathway excites + inhibits motility

sympathetic pathway inhibits effects of motility

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16
Q

what are the 2 distinct areas of motor activity in the stomach ?

A

proximal

distal

17
Q

what is the migrating motor complex ?

A

when indigestible solids that have failed to pass through the pylorus can pass into the small intestine between meals
is a result of motor activity

18
Q

what is the bodies response to the stomach filing ?

A

stomach pressure remains constant until around 1l of food ingested due to plasticity of smooth muscles
peristaltic waves move toward pylorus at rate of 3 per minute
basic electrical rhythm initiated by pacemaker cells

19
Q

where does the most vigorous peristalsis + mixing occur

A

near the pylorus

20
Q

what happens to chyme at the pylorus ?

A
  • delivered in small amounts into the duodenum

- or if to big forced backwards into stomach for further mixing

21
Q

what is gastric emptying regulated by ?

A

neural enterogastric reflex

hormonal mechanisms

22
Q

how do mechanisms work to regulate gastric emptying ?

A

inhibit gastric secretion + duodenum filling
carbohydrate rich chyme quickly moves through duodenum
fat-laden chyme is digested more slowly causing food to remain in stomach for longer

23
Q

how does secretin help regulate gastric activity ?

A

stimulates HCO3 secretion

inhibits stomach activity

24
Q

how does CCK regulate gastric activity ?

A

stimulates gallbladder contraction + emptying

inhibits stomach activity

25
Q

how does motilin regulate gastric activity ?

A

increase gastric motility

increases intestinal motility

26
Q

how does neuronal control regulate gastric activity ?

A

short reflexs operating in the enteric nervous system inhibit gastric secretions/ contractions
long reflexes operating via the CNS alter autonomic nerve activity

27
Q

what is the enteric nervous system ?

A

intrinsic NS that controls different functions of GI tract

28
Q

why is the ENS describe as separate from the ANS ?

A

because it has its own independent reflex activity

29
Q

what are the 2 types of ganglia in the ENS ?

A

myenteric ( auerbach)

submucosal (meissner)

30
Q

where is the myenteric plexuses located ?

A

inner + outer layers of the muscular external

31
Q

where the submucosal plexuses located ?

A

in the submucosa

32
Q

what do neurons in the ENS respond to ?

A

mechanical deformation
chemical stimuli
temperature

33
Q

what do receptors in the duodenum + jejunum sense ?

A

acidity
osmotic pressure
certain fats
amino acids + peptides

34
Q

what sympathetic nerves innervate the GI tract ?

A

coelic
superior + inferior mesenteric
hypogastric plexuses

35
Q

what parasympathetic nerves innervate the GI tract ?

A

preganglionic
cholinergic fibres
terminate on ganglion cells in the intramural plexuses