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Physiology > 3 Gastrointestinal Physiology > Flashcards

3 Gastrointestinal Physiology Flashcards

1
Q

4 main topics we discuss

A

motility
secretion
digestion
absorption

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2
Q

organs of the GI tract

A 
oral cavity
pharynx
esophagus
stomach
small intestine
large intestine
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3
Q

what are the two GI muscular layers?

A
  • outer, longitudinal layer (shortens tract)

* inner, circular layer (constricts tract)

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4
Q

what muscular layer is close to lumen?

A

circular

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5
Q

sphincters are located between?

A

major compartments

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6
Q

what is similar between cardiac and smooth muscle innervation?

A

NOT every cell is innervated. They form functional syncytium with gap junctions and ephhaptic conduction
**opposite for skeletal

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7
Q

organelles found in smooth muscle are?

A
  • poorly developed SR
  • less organized contractile units
  • **lack troponin (use calmodulin instead)
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8
Q

most Ca for smooth muscle comes from? binds to?

A

comes from ECF

*bins to calmodulin bc smooth muscle lacks troponin

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9
Q

two types of electrical waves?

A

slow waves

spikes

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10
Q

slow waves are also called?

A

basal electrical rhythms (BERs)

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11
Q

what are slow waves?

A

spontaneous oscillations of membrane potential= non-propagated (local) potentials

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12
Q

are slow waves or spikes non-propagated or propagated?

A

slow waves= NON-propagated

spikes= propagated

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13
Q

slow waves do not result in muscle contraction because?

A

they don’t usually reach the muscles cell’s threshold for excitation

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14
Q

do slow wave frequency vary? Exs?

A

YES

  • stomach= 3/min
  • duodenum= 12/min
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15
Q

spikes are also called?

A

action potentials

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16
Q

when do action potentials occur?

A

when threshold is reached= propagated potentials

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17
Q

what are “additional signals” for spikes?

A

nervous, mechanical, hormonal

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18
Q

what are additional signals for spikes required for? (explain process)

A

for slow waves to become spikes
(additional signals > BERs reach threshold > AP > contraction > travels down GI in wave-like fashion = propagated potentials

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19
Q

what are the two contraction types?

A

1) tonic= common in sphincters

2) phasic= more coordinated, but not as rhythmic as cardiac

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20
Q

describe tonic contractions. last how long? purpose? Exs?

A
  • sustained contractions
  • last min-hrs
  • purpose to prevent forward flow until ready
  • sphincters and upper stomach (fundus)
21
Q

describe phasic contractions. last how long? purpose? Exs?

A
  • rapid contractions -contract and relax FAST
  • last seconds
  • purpose to mix and move
  • esophagus, small intestine, lower stomach (antrum)
22
Q

what are 4 factors regulating GI muscle contraction?

A

1) entertic nervous system
2) extrinsic NS
3) stretch
4) hormones

23
Q

what are the enteric nervous system plexuses? location?

A

1) myenteric plexus
- – b/w inner long and outer circle muscles
2) sunmucosal plexus
- – closer to absorptive surfaces in Submucosa

24
Q

myenteric plexus controls?

A

movement: controls and coordinates motility of the gut

25
Q

submucosal plexus controls?

A

secretions of the gut

26
Q

Myenteric and submuscoal plexuses are also known as?

A
  • myenteric= Auerbach’s plexus

* submucosal= meissner’s plexus

27
Q

are efferent or afferent fibers found in the plexuses?

A

both

28
Q

does the enteric nervous system (myenteric or submucosal plexuses) function dependently or independently of extrinsic NS?

A

BOTH

*independent OR function in conjunction with autonomic extrinsic NS

29
Q

for the enteric NS, afferent fibers carry what information?

A

sensory

  • myenteric= pressure
  • submucosal= chemical
30
Q

how do enteric NS fibers communicate?

A
  • interconnect/communicate to activate or inhibit each other
  • interconnect/communicate with EXTRINSIC (autonomic) NS
  • over 20 neurotransmitters have been identified
31
Q

what does extrinsic NS mean?

A

OUTSIDE of the gut

  • autonomic
  • sym and para
32
Q

where do the sym and para fibers originate for extrinsic NS?

A
  • Sym= thoracolumbar spinal cord (T5-L2)

* para= originate in vagus and pelvic splanchnic nerves (S2-4)`

33
Q

How does para and sym affect the GI compared to cardio?

A
  • Sym= slows, inhibits, diminishes GI
  • –decreases motility and secretions
  • Para= activated, speeds up GI
  • – increases motility and secretions
  • ***opposite is true for cardiac
34
Q

what is the affect of stretch on the gut?

A

increases motility, contractility and secretions

35
Q

the gut has a ‘reflex arc’, this means?

A

that the plexuses have afferent and efferent fibers to the gut

36
Q

what are 4 major hormones that affect gut motility?

A

1) gastrin
2) GIP
3) CCK
4) secretin

37
Q

gastric mucosa secrets?

A

gastrin

38
Q

gastrin is secreted into?

A

CIRCULATION** not the lumen

39
Q

duodenal mucosa secrets what hormones?

A

GIP
CCK
secretin

40
Q

GIP stands for?

A

glucose-dependent insulinotrophic peptide (GIP)

41
Q

CCK stands for?

A

cholecystokinin

42
Q

gastrins affect on GI motility?

A

increase

43
Q

GIP, CCK, and secretin on GI motility?

stimulate release of what?

A

decrease (inhibits stomach)

**release of enzymatic carbonate

44
Q

protein, stretch, and vagus stimuli cause the release of what hormone?

A

gastrin

45
Q

CHO and fat stimuli in SI cause the release of what hormone?

A

GIP from pancreas

46
Q

Fat and protein stimuli in SI cause the release of what hormone?

A

CCK from pancreas

47
Q

acid stimuli in SI cause the release of what hormone?

A

secretin

48
Q

what are the two major functions of the release of duodenal hormones?

A

1) decrease motility and slows emptying of the stomach into the intestine
2) causes release of particular pancreatic enzymes to break down food

Physiology (42 decks)

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