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Physiology > Intro to GI U6L01 > Flashcards

Intro to GI U6L01 Flashcards

1
Q

a series of musclar sphincters regulate unidirectional flow between diff sections of the gi tract via ___ mechanism

A

inherent myogenic

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2
Q

___ and ___ are necessary to promote digestion, absorption, and detoicfication of ingested materials

A

substantial fluid shifts and ph changes

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3
Q

the primary nerve nets or plexuses in the enteric NS are

A

myenetric and submuscosal

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4
Q

The myenteric plexus (Auerbach’s) is between the ___ and ___ layers of the GI tract

A

longitudinal and circular muscle

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5
Q

myentric plexus extends from the___ to the ___

A

esophagus to the rectum.

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6
Q

stimu. of the myeneric plexus increases ___ (3)

A
  1. increases tonic contraction or ‘tone’ of the gut
  2. the intensity of rhythmic /phasic contractions
  3. and velocity of conduction of excitatory waves (thus enhancing peristalsis)
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7
Q

The submucosal plexus (Meissner’s) is between the c

A

circular muscle and submucosa in the small and large intestines

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8
Q

primary function of the submuosal plexus

A

primarily involved with: controlling

  1. local intestinal secretions
  2. absorption
  3. contraction of the submucosal muscle which affects local infolding of the GI mucosa.
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9
Q

The sphincters are essentially ___-way valves

A

one

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10
Q

spchinters maintain a ___ pressure

A

positive

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11
Q

Activation of____ neurons leads to transient relaxation of the sphincters (causing release of food)

A

inhibitory motor

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12
Q

___ maintains the highest resting pressure of all sphincters

A

upper esophageal sphincter (UES)

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13
Q

upper esophageal sphincter (UES) prevents

A

air from entering the esophagus

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14
Q

sphinters made of skeletal muscle

A

upper esophageal sphincter

external anal sphincter

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15
Q

what controls the upper esophageal sphincter?

A

the swallowing center in the medulla

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16
Q

lower esophageal sphincter (LES) separates the ___ and ___

A

esophagus and the stomach

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17
Q

esophageal sphincter amde of smooth muscle

A

lower esophageal

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18
Q

lower esophageal sphincter (LES) functions

A
  1. to coordiante the passage of food into the stomach
  2. prevent the refleux of gastric contents
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19
Q

An incompetent ___can lead to heartburn/acid indigestion

A

LES

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20
Q

the resting pressure of the pyloric sphincter contributes to regulation of

A

gastric emptying

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21
Q

the resting pressure of the pyloric sphincter contributes to prevention of

A

duodenal-gastric reflux

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22
Q

Reflux of bile acids and digestive enzymes can lead to (3)

A

gastritis, ulcer formation, and risk of perforation

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23
Q

ileocecal sphincter is a valve-like structure that separates the ___ and ___

A

ileum and cecum

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24
Q

function of the ileocecal sphincter

A

reventing back flux of colonic contents into the ileum

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25
Q

. While we ingest ~2 liters (L) of fluid in food and drink each day, the GI tract adds____ of secretions to facilitate digestion and absorption of the nutrients.

A

~8 L

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26
Q

what in the GI system adds the most fluid?

A

pancreatic juice

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27
Q

___ absorbs the most fluid

A

small intestine

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28
Q

relatively, how much fluid is excreted in feces?

A

very little compared to what is absorbed, only 100-200 ml

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29
Q

____ in the oxyntic glands of the stomach acidify the contents of the stomach to promote digestion, and breakdown of ingested bacteria and antigens.

A

Parietal cells (oxyntic)

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30
Q

with acidic chyme in the stomach, the hydrogen ion concentration is ___ times that of the arterial blood.

A

~3 million

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31
Q

Secretion of HCO - into the lumen of the duodenum is by the ___

A

exocrine pancreas

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32
Q

___ by the exocrine pancreas neutralizes the acidic chyme being delivered from the stomach to duodenum.

A

Secreted HCO -

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33
Q

The two primary smooth muscle layers controlling motility are the___ and ___ muscles in the gut

A

e circular and longitudinal

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34
Q

enteric nervous sytem is called the minibrain

A

because of its plexuses

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35
Q

the ens is able to function indepdently responding to input from the local environment even in the abscense of

A

extrinisc innervation

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36
Q

musculomotor and secretomotors can alter

A

smooth m. activity

secretion and absorption of fluid/exlectrolytes

submucosal blood vessels

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37
Q

ENS activity is modulated by input from

A

the symps and parasymp

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38
Q

processing of sensory signals is a primary function of the ____ ENS neural network

A

intrinsic

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39
Q

sensory neurons monitor changes in luminal activity in the ENS

they activate ___. what does this do?

A

interneurons, which relay signals to activate efferent secretomotor neurons

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40
Q

Mechanoreceptors sense stretch of the smooth muscle, and the generated signal is transduced through the _____ plexus, stimulating contractions.

A

myenteric

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41
Q

Chemoreceptors sense the chemical composition of the chyme and regulate (2)

A

motility and secretion of buffers to control luminal pH during the influx of acidic chyme into the duodenum.

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42
Q

____receptors control the amount of chyme entering the small intestine

A

osmoreceptors

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43
Q

___ fibers (vagus and pelvic nerves) terminate on postganglionic cholinergic or peptidergic neurons located in the plexuses.

A

Parasympathetic preganglionic

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44
Q

____ activation leads to increased motility in the wall of the gut, relaxation of sphincters, and enhanced secretions

A

PNS

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45
Q

___ reflexes are prominent in coordinating GI function.

A

Vagovagal

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46
Q

The vagus innervates the proximal 2⁄3 of the ENS from the pharynx to the ___

A

beginning of the distal colon

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47
Q

The ___ nerves innervate the distal 1/3 of the colon

A

pelvic

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48
Q

the SNS innervates the enteric NS via postganglionic fibers from the (4)

A
  1. celiac plexus
  2. hypogastric
  3. and the superior & inferior mesenteric ganglia
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49
Q

SNS activation inhibits digestion and absorption by (4)

A
  1. relaxing the gut wall
  2. reducing secretions
  3. contracting sphincterss
  4. diverting blood flow from the GI tract by contracting the vasculature
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50
Q

what is the 5 layer heirachy that determines the moment to moment motor behavior of the digestive tract

A
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51
Q

___ are pacemakers in the gi tract that produce continual slow intrinsic exciation

A

intersitial cells of cajal

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52
Q

contraction of gi muscle wall occurs only when ___ are generated at the pearks of

A

the slow waves produced by interstial cells of cajal

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53
Q

2 types of waves produced by the ICC pacemakers

A
  1. slow waves – undulating changes in resting membrane potential
  2. spike pontetials – produced whent he threshold is reached during the paltea phase of the slow wave
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54
Q

how does PNS increase the contractility of the gi system?

A

by increasing the spike potentials of the pacemaker cells (not the frequency)

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55
Q

in GI, action potentials are produced largely by ___ entry through ____

A

Ca2+ entry through L-type VSCCs

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56
Q

The ENS controls the ___ and ___ of spread of electrical activity in the muscle using both excitatory (ACh, substance P) and inhibitory (VIP) motor neurons.

A

distance and direction

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57
Q

in the stomach there are ____ contractions in addition to the contractions generated to move food along

A

tonic contractions always occuring

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58
Q

____ connect the ICCs to the circular muscle.

A

Gap junctions

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59
Q

Slow wave motor patterns are influenced by (3)

A

hormones, paracrine factors, the ANS

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60
Q

Slow wave frequency is highest in the___

A

small intestine

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61
Q

Slow wave frequency is lowest in the

A

stomach

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62
Q

The maximal contractile frequency in the muscle does not exceed the

A

frequency of slow waves

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63
Q

Neural and hormonal input modulate the production of action potentials and thus the

A

strength of muscle contractions.

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64
Q

Failure of __can lead to disordered motility including spasm and abdominal cramping.

A

ENS control

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65
Q

small inestinal motility mixes and moves chyme by ___

A

segmental and peristaltic contractions

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66
Q

Segmental/mixing/non-propulsive Contractions are local events and typically occur in different segments at a frequency of ~___ per minute.

A

2-3

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67
Q

The maximal frequency of segmental contractions in the small intestine is no more than 12 per minute, and is determined by the___

A

frequency of electrical slow waves

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68
Q

Excitation from the___ plexus is important for Segmental/mixing/non-propulsive contractions

A

myenteric nerve

69
Q

effect of atropine (muscarinic cholinergic anatagonist) on Segmental/mixing/non-propulsive contractions

A

weak contractions, showed the importance of the myenetric n. plexus

70
Q

Peristaltic contractions - move material from __ to )))

A

mouth to colon

71
Q

___ hrs are needed to move chyme from the pylorus to the ileocecal valve.

A

~3-5

72
Q

Peristalsis is intensified after a meal by stretch of the duodenal wall upon entry of

A

chyme.

73
Q

____ reflex enhances peristaltic motility and secretions.

A

gastroenteric

74
Q

gastroileal reflex triggers opening of the ___ valve to permit passage of chyme from small to large intestine

A

ileocecal

75
Q

distension of the ileum leads to ___ of the sphincter

A

relaxation

76
Q

distension of the ascending colon leads to ___.

A

contraction

77
Q

___ reflex decreases gastric motility and secretions

A

enterogastric

78
Q

what does the enterogastric reflex stimulate?

A

contraction of the pyloric sphincter

79
Q

intestinatal motlity after ingestion of a meal is characterzed by mixing to

A

optimize contact between ingested food and digestive secretions

80
Q

intestinatal motlity after ingestion of a meal is characterzed by circulation of intestinal contents to faciliate

A

contact with the mucosa

81
Q

intestinatal motlity after ingestion of a meal is characterzed by net propulsion of contents in a

A

aboral direction

82
Q

____ forms pockets of chyme and serves to mix and propel the chym

A

Segmentation

83
Q

rritation of the intestinal mucosa by infectious agents, for example, causes a

A

peristaltic rush/diarrhea that serves to clear the intestine of the irritant.

84
Q

myentric reflex or law of the gut is also called

A

peristalsis

85
Q

proximal to the bolus is something that causes ____ of the longitudinal muscle

A

excitation

86
Q

distal to the bolus (the receiving end) is something that causes ____ of the circular muscle

A

relaxation

87
Q

peristalsis occurs with the simultaneous shortenin and relaxation of the __ and __ muscles to move the bolus

A

the circular and longitudinal muscles

88
Q

circular muscle or longitudinal muscles are thicker?

A

circular

89
Q

circular muscle is innervated by ___ motor neurons

A

excitatory and inhibitory

90
Q

longitudinal muscle is innervated by ___ motor neurons

A

excitatory

91
Q

Physiological ileus is the

A

absence of motility in the small & large intestine

92
Q

Is Physiological ileus normal or abnormal?

A

normal state.

93
Q

with Physiological ileus, A subset of inhibitory neurons are active and suppress the response of the

A

circular muscle to the electrical slow waves.

94
Q

Pathological ileus (paralytic ileus) is a state when the normal periods of quiescence are much ___.

A

longer

95
Q

with Pathological ileus the inhiitory neurons are

A

abnormally active

96
Q

altered motility and delayed transit is common after (3)

A

abdominal surgery (postoperative ileus), anticholinergic or opiate drug treatment.

97
Q

Fasting is an interdigestive state that is characterized by

A

long periods of quiescence in conjunction with short rhythmic waves of strong propulsive contractions that pass down the distal stomach and small intestine.

98
Q

short rhythmic waves of strong propulsive contractions during the resting phase are called

A

Migrating Motor Complex

99
Q

3 phases of migrating motor complex

A

quiescence (I), little activity (II), and strong activity (III)

100
Q

function of the migrting motor complex

A

‘sweep’ the stomach and small intestine of residue including undigested food/fiber, bacteria

101
Q

during ___ the pyloric sphincter is inhibited and particles larger than 2 mm can pass into the duodenum.

A

migrating motor complex

102
Q

migrating motor complex is observed ___

A

3 hours after the last meal

103
Q

Migrating Motor Complex occurs in intervals of

A

90 minutes

104
Q

where does the igrating motor complex start

A

Begins in the distal 1/3 of the stomach

105
Q

Motilin is synthesized in the

A

duodenal Mo cells

106
Q

motlin is released into the circulation and stimulates the

A

contractions (5-10 min) seen during the active phase

107
Q

Motilin acts through the ___ to stimulate contractions.

A

ENS and ANS

108
Q

in the absence of the MMC, indigestible material called ___ accumulate

A

“bezoars”

109
Q

significance of “bezoars”

A

can obstruct the lumen of the stomach in particular.

110
Q

effect of vagotomy on MMC?

A

reduces constracile acitivty

111
Q

is MMC an intrisnic or extrinsic property of the gi tract

A

intrinsic

112
Q

3 phases of swallowing

A
  1. voluntary stage

involuntary events

  1. pharyngeal phase
  2. esophageal phase
113
Q

what does the volutnary stage of swallowing involve? (2)

A
  1. shaping of food into a bolus
  2. Raising of the tongue against the hard palate to create a pressure gradient that pushes the bolus
    into the pharynx.
114
Q

___ activates sensory neurons that project via the vagus and glossopharyngeal
nerves to the swallowing center in the medulla.

A

Food in the pharynx

115
Q

Efferent impulses are sent back to the pharynx, esophagus, esophageal sphincters and stomach
causing: (3)

A
  1. the soft palate to pull upward (preventing food reflux into the nasopharynx)
  2. movement of epiglottis and pharynx to prevent food from entering trachea
  3. relaxation of the UES
116
Q

what is the pharyngeal phase of swallowing

A
  1. soft palate pulling upward
  2. movement of the epiglottis and pharynx
117
Q

The ___ also initiates a primary peristaltic wave that propels food through the open UES

A

swallowing reflex

118
Q

with the opening of the LES and peristalsis of the esophagus the stomach

A

undergoes receptive relaxation

119
Q

what happens If the primary wave fails to move all food into the stomach?

A

a secondary peristaltic wave results from distension of the esophagus

120
Q

in the pahryngeal phase tactile areas in the pharnx transmit impusles tot he swallowing center in the ___

A

medulla

121
Q

nerves activated during th epharyngeal phase include

A

5, 9, 10, 12

122
Q

during the pharyngeal phase, the swallowing center of the medulla inhibits

A

the respiratory center

123
Q

pharynx and upper 1/3 of the esophagus are ___ muscle,

A

striated

124
Q

pharynx and upper 1/3 of the esophagus are controlled by skeletal nerve impulses from ___

A

CN 9 and 10

125
Q

disorders of swallowing can occur with damage to nerves

A

5, 9, 10

126
Q

diseases that damage the swallowing center include ___ and ___

A

poliomyelitis and encephalitis

127
Q

___ and ___ are two diseases that can cause paralysis of the swallowing muscle

A

muscular dystrophy and myasthenia gravis

128
Q

what is the signfiicance of the swallowing mechanism duirng sedation?

A

deep anesthesia inhibits the swalowing mechanism

its pts vomit on the operating table it will suck into the trachea instead of swallowing it

129
Q

nuclei initiated during deglutition

A

nucleus ambiguus cn 9 and 10

dorsal mtoor nucleus of vagus

and tohers

130
Q

pressure in UES after swallowing

A
131
Q

pressure in LES after swallowing

A
132
Q

pressure in stomach after swallowing

A
133
Q

what is receptive relaxation?

A

transient relaxation of the proximal stomach with each bolus of food

134
Q

Receptive relaxation in the lower esophageal sphincter and fundus is primarily regulated by a ___ reflex after swallowing

A

vagovagal

135
Q

The transmitter released by the postganglionic vagal fibers during receptive relaxation?

A

vasoactive intestinal polypeptide (VIP).

136
Q

The secondary wave begins at the point of ____ and travels downward.

A

distension

137
Q

In the stomach, receptive relaxation results in an increase in intragastric ____

A

volume (not presure)

138
Q

As food accumulates in the stomach there is a gradual _____ of the entire stomach, called accommodation,

A

relaxation

139
Q

accodomation allows storage of food without an

A

increase in intragastric pressure

140
Q

the ___ reflex mediats accommodation

A

vagovagal

141
Q

gastric empyting is slow after

A

ingestion of a high fat meal

142
Q

gastric empyting is _____ after ingestion of liquid salide

A

rapid

143
Q

food entering the stomach does not cause a proportionate increase in intragastric pressure until a ___

A

threshold is reached (you really pig out)

144
Q

if you cut the vagus, compared to normal the intraluminal pressure

A

increases much earlier with filling of food

145
Q

Modification of gastric contents is associated with multiple feedbakc mechanism, most which arise from the

A

duodenum

146
Q

modificaiton of gastric contents by the duodneum almost alays resuts in a

A

delay in gastric emptying

147
Q

chemoreceptors and mechanoreceptors in the small intestine-sense (3)

A
  1. low pH (high acidity)
  2. a high content of calories, lipid, or some amino acids (i.e., tryptophan)
  3. or changes in osmolarity.
148
Q

effect of cck on gastric contents?

A

CCK is a major player in decreasing the rate of gastric empyting

149
Q

Delayed gastric emptying represents: the coordinated function of

A
  1. fundic relaxation
  2. inhibition of antral motor activity
  3. stimulation of isolated, phasic contractions of the pyloric sphincter
  4. altered intestinal motor activity.
150
Q

when LES is incompetant, what two issues can you have?

A

achalasia and GERD

151
Q

achlasia is due to

A

the failure of LES to relax during swallowing

152
Q

The resting tone of the lower esophageal sphincter (LES) is usually ____

A

high, preventing reflux of stomach contents

153
Q

As the bolus of food reaches the LES, local____ is released, and the sphincter tone relaxes

A

vasoactive intestinal peptide (VIP, and probably NO as well)

154
Q

gastroesophageal reflux disease (GERD) cause?

A

failure of the ability to maintain LES tone

155
Q

damage to the myenteric plexus in the lower 2/3 of the esophagus (smooth muscle) can cause the lower esophagus to be

A

spastically contracted (due to a lack of inhibitory motor neuron activity)

and unable to transmit the signal for receptive relaxation to the LES

156
Q

functionally the stomach is divided into a

A
  1. proximal gastric reservoir – fundus and 1/3 of the body
  2. distal antral pump – caudal 2/3 of the body, antrum, pyloris
157
Q

Muscles in the___ portions of the stomach are adapted for maintaining continuous contractile tone.

A

gastric reservoir

158
Q

in the stomach, the ___ is where you get the phasic contractions

A

antrum

159
Q

function of the gastric reservoir? (2)

A
  1. to accommodate arrival of a meal without a significant increase in intragastric pressure
  2. to maintain constant compressive forces on the contents of the reservoir which push the contents into the antral pump region
160
Q

failure of the gastric reservoir leads to

A

bloating, epigastric pain, and nausea/dyspsiea

161
Q

the ___ propels chyme towards the gastroduodenal junction

A

antral pump

162
Q

Action potentials in the antral pump are ___.

A

myogenic

163
Q

what nt release increases contractions of the antral pump

A

acetlyhcoline from the PNS

164
Q

what nt release decreases contractions of the antral pump

A

norepinephrine contractions from the SNS

165
Q

the ___ churns the trapped bolus

A

antrum

166
Q

when the pylorus is closed, what happens after grinding?

A
167
Q

processes of propulsion, grinding, and retropulsion repeat multiple times until

A

the gastric contents are emptied.

168
Q

Particles larger than____ are initially retained in the stomach but are eventually emptied into the duodenum by MMCs during the interdigestive period

A

2 mm

169
Q
A

Physiology (5 decks)

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