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unit 6: physiology > Intro to GI (1) > Flashcards

Intro to GI (1) Flashcards

1
Q

How many calories a day does a sedentary adult require?

A

30 kcal/kg body weight per day

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2
Q

Which sphincter has the highest resting pressure?

A

UES

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3
Q

What type of muscle is the UES, what does it do?

A

striated muscle

prevents air from entering esophagus

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4
Q

What type of muscle is the LES? What does it do?

A

smooth muscle

prevents reflux of gastric contents into esophagus

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5
Q

What does the pyloric sphincter separate? What does it do?

A

duodenum and stomach

regulates gastric emptying and prevents duodenal reflux

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6
Q

What does IBS entail?

A

overgrowth of bacteria in the small intestine

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7
Q

What sphincter is incompetent in heartburn?

A

LES

GERD

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8
Q

What type of muscle makes up the internal and external anal sphincters?

A

internal - smooth muscle

external - skeletal muscle

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9
Q

Describe the fluid shifts during digestion?

A

we ingest 2 L, GI tract adds 8 L of secretions

we only excrete 100-200 mL in feces

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10
Q

What is the pH of the stomach and how is this pH achieved?

A

1-2

parietal cells

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11
Q

How is the pH neutralized in the duodenum?

A

pancreas excretes bicarbonate

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12
Q

Myenteric (auerbach’s plexus)

  1. btwn what two layers?
  2. extends from where to where
  3. function
A
  1. btwn longitudinal and circular
  2. extends from proximal end of esophagus to rectum
  3. peristalsis
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13
Q

Submucosal (meissener’s) plexus:

  1. btwn what two layers?
  2. extends from where to where?
  3. function
A
  1. btwn circular and submucosal
  2. in small and large intestines
  3. controls secretion, absorption, cntrxn
    affects local infolding of mucosa
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14
Q

What layer of the small intestine is responsible for infolding ?

A

muscularis mucosae

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15
Q

Is input from other structures necessary for the GI tract to function?

A

NO0O..able to function independently

- does receive input however

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16
Q

Where is 95% of serotonin and 70% of the immune system located?

A

the great and wonderful gut

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17
Q

What are the three types of receptors in the GI system?

A
  1. mechanoreceptors
  2. chemoreceptors
  3. osmoreceptors
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18
Q

What is the PNS affect on the GI system?

A

inc motility and relaxation of sphincters

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19
Q

What NTs does the PNS use?

A

ACh for postganglionic cells

some use peptides too

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20
Q

What is the differentiation on what the vagus and pelvic autonomic nerves innervate?

A

vagus - proximal 2/3 from pharynx to distal colon

pelvic- distal 2/3

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21
Q

What NT does the SNS release to inhibit secretions, absorption and motility?

A

NE

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22
Q

What CNs control initiation of salivation upon seeing, smelling, tasting during the cephalic stage?

A

CN 7 and 9

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23
Q

What are some of the functions CN10 induces during the cephalic and gastric phases?

A
  1. initiates acid production when food is in mouth
  2. stimulates pancreatic enzyme prod.
  3. relaxes the sphincter of Oddi
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24
Q

What does CN10 induce during the intestinal phase?

A

pancreatic enzyme production and buffer secretion

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25
Q

What regulates primary peristalsis?

A

CN10 through the medulla and vagus swallowing center

26
Q

What are the interstitial cells of cajal and where are they found?

A

myenteric plexus
generate electrical slow waves which flow through circular muscle through gap junctions
5-15 mv

27
Q

When are APs produced in the gut? How does this occur?

A

When spike potentials reach threshold: 40 mv

Ca2+ rushes in through L type channels

28
Q

What AP lasts longer, nerve or gut?

A

gut –>10-40 times longer

29
Q

Where is slow wave frequency the highest? the slowest?

A

highest - small intestine: 12/min

slowest - stomach: 3/min

30
Q

What modulates the production of APs in the gut?

A

neural and hormonal output

31
Q

What is the effect of atropine on the gut?

A

weak peristalsis

32
Q

What direction does peristalsis conduct food?

A

aboral - orad to caudad

33
Q

How many hours does it take to move food from the pylorous to ileocecal valve?

A

3-5 hours

34
Q

What is the function of the gastroenteric reflex?

A

enhances peristaltic motility and secretions

35
Q

What is the function of the gastroileal reflex?

A

opening of ileocecal valve to permit passage

36
Q

What is the function of the enterogastric reflex?

A

decreases gastric motility and secretions

-stim cntrxn of pyloric sphincter to inhibit backflow

37
Q

Describe what muscles contract and relax ahead and behind a bolus during the myenteric reflex

A
  1. behind: circular contracts, longitudinal relaxes
    -propulsion
    -depolarization by the ascending pathway
    (ACh, substance P)

2.ahead: circular relaxes, longitudinal contracts
-lumen expands
-hyperpolarization by the descending pathway
(VIP, NO)

38
Q

What neurons control the circular and longitudinal muscles?

A

circular- inhibitory and excitatory

longitudinal - excitatory

39
Q

How does a pathological ileus differ from physiological ileus?

A

normal periods of quiescence are much longer
inhibitory neurons are abnormally active
passage of stool and gas are impaired

40
Q

What are the three phases of the migrating motor complex, and when does this occur?

A

during fasting:

  1. quiescence
  2. little activity
  3. strong activity
41
Q

What is the function of the MMC?

A

sweep the stomach and small intestine of residue

42
Q

What sphincter is inhibited in the MMC, and what is the result?

A

pyloric sphincter is inhibited

particles larger than 2 mm can pass into duodenum

43
Q

When and where is the MMC occuring?

A

3 hours after last meal at cyclic intervals of 90 min
-w/ ingestion of food - normal patterns resume

begins in distal 1/3 of stomach -> ileum
-empties material into colon

44
Q

What NT stimulates the contractions seen during the active phase of MMC?

A

motilin - secreted from duodenal Mo cells

-acts through ENS and ANS

45
Q

What are bezoars?

A

indigestible material that accumulates if the MMC does not occur

46
Q

How would a vagotomy affect the MMC?

A

it would reduce contractile activity

47
Q

What is the voluntary stage of swallowing?

A

shaping of food into bolus
raising of tongue against hard palate
pushes bolus into pharynx

48
Q

What is the involuntary pharynx phase of swallowing?

A

soft palate blocks nasopharynx
epiglottis blocks trachea
relaxation of UES

49
Q

What is the involuntary esophageal phase of swallowing?

A
  • primary peristaltic waves propels food through open UES and then it closes
  • continued peristalsis until LES opens
  • receptive relaxation of stomach
50
Q

What are the afferent limbs and efferent limbs in the pharynx?

A

afferent: CN 5 and 9 to swallowing center
efferent: CN 5,9, 10, 12

51
Q

What is accomodation in the stomach?

A

increase in volume without inc in pressure

52
Q

What can cause disorders of swallowing?

A

damage to cn 5, 9 , 10
poliomyelitis, encephalitis
muscular dystrophy, myasthenia garavis
anesthesia

53
Q

What regulates receptive regulation in the LES and fundus ?

A

postganglionic vagal fibers that release VIP

54
Q

Do the contents of a meal influence the rate of gastric emptying?

A

yes - sensed by chemoreceptors and mechanoreceptors to optimize absorption
-high calories, low pH–> slow

55
Q

What is gastric emptying mediated by?

A

combo of neural and hormonal signals

vagus nerve, secretin, CCK, GIP

56
Q

What is achalasia?

A

failure of the LES to relax during swallowing

-buildup of food in esophagus

57
Q

What is the proximal gastric reservoir?

A

fundus and 1/3 of body

  • continuous contractile tone
  • accomodation
  • compressive force on contents
58
Q

What is the distal antral pump?

A

caudal 2/3 of body, antrum, pyloris

propels chyme towards GD junction

59
Q

What layers of muscle does the stomach have?

A

longitudinal, circular, oblique

60
Q

Describe churning in the stomach?

A

bolus trapped near antrum and churned
only particles smaller than 2 mm expelled to duodenum
particles >2 mm initiatially retained in stomach are cleared through the MMC

unit 6: physiology (13 decks)

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