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BRS (PHYSIO) > Gastrointestinal > Flashcards

Gastrointestinal Flashcards

1
Q

Epthelial cells are specialied in different part of the GI tract for ________or _________

A

secretion or absorption

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2
Q

Contraction causes a change in the surface area for secretion or absorption

A

Muscularis mucosa

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3
Q

Contraction causes a decrease in diameter of the lumen of the GI tract

A

Circular muscle

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4
Q

Contracion causes shortening of a segment of the GI tract

A

Longitudinal muscle

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5
Q

Comprise the enteric nervous system of the GI tract

Integrate and coordinate the motility, secretory, and endocrine funcrions of the GI tract

A

Sumbmucoasl (meissner plexus) and myenteric plexus

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6
Q

the _____________of the GI tract comorises both extrinsic and intrinsic nervous systems

A

ANS

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7
Q

Extrinsic innervation

A

PNS and SNS

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8
Q

carry information from the brain ste and spinal cord to the GI tract

A

Efferent fibers

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9
Q

Carry sensory information from chemoreceptors and mechanoreceptors in the GI tract to the brain stem and spinal cord

A

Afferent fibers

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10
Q

_______________is usually excitatory on the functions of the GI tract

A

Parasympathetic

  • carried via the vagus and pelvic nerves
  • Preganglionic PS fibers synapse in the yenteric and submucosal plexus
  • cell bodies in the ganglia of the plexuses then send information to the smooth muscle, secretory cells, and endocrine cells of the GI tract
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11
Q

The _______ innervates the esophagus, stomach, pancreas, and upper large intestine

A

Vagus nerves

  • Reflexes in which both afferent and efferent pathways are contained in the vagus nerve are called vasovagal reflexes
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12
Q

the _____ innervates the lower large intestine, rectum, and anus

A

Pelvic nerve

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13
Q

___________ is usually inhibitory on the functions of the GI tract.

A

Sympathetic nervous system

  • Fibers originate in the spinal cord between T8 - L2
  • Preganglionoc sympathetic cholinergic fibers synapse in the prevertebral ganglia
  • Postganglionic sympathetic adrenergic fibers leave the prevertebral gangla and synapse in the myenteric and submucosal plexues. Direct postganglionic adrenergic innervation of blood vessels and some smooth muscle cells also occurs
  • Cell bodies in th eganlia of the plexuses then send information to the smooth muscle, secretory cells and endorcrine cells of the GI tract
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14
Q

Coordinates and relays information from the PNS and SNS to the GI tract

A

Intrinsic nervous system (enteric nervous system)

  • uses local reflexes to relay within the GI tract
  • controls most functions of the GI tract, especially motility and secretion, even in the absence of extrinsic innervation
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15
Q

Primarily controls the motility of the GI smooth muscle

A

Myenteric plexus (Auerbach plexus)

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16
Q

Primarily controls secretion and blood flow

Receives sensory information and chemoreceptors and mehanoreceptors in the GI tract

A

Submucosal Plexus (Meissner plexus)

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17
Q

“official” GI hormones

A

gastrin

cholestokinin

seccretin

glucose insulinotropic eptide (GIP)

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18
Q

Increases H+ secretion. Stimulates growth of gastric mucosa

A

gastrin

  • Stimulus:
    • small peptides and amino acids
    • distention of stomach
    • vagus (via GRP)
    • inhibited by H+ in stomach
    • Inhibited by somatostatin
  • Gastrin -CCK family
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19
Q

Stimulates cobtraction of gallbladder and relaxation of sphincter of Oddi.

Increase pancreatic enzyme and HCO3 secretion

Increase growth of exocrine pancreas/gallbladder

Inhibits gastric emptying

A

CCK

  • Stimulus
    • small peptides and amino acids
    • fatty acids
  • gastrin-CCK family
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20
Q

Increase pancreatic HCO3 secretion

Increase Biliary HCO3 secretion

Decrease gastric H+ secretion

A

Secretin

  • Stimulus
    • H+ in duodenum
    • Fatty acids in the duodenum
  • Secretin-glucagon family
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21
Q

Increase insulin secretion

Decrease gastric H+ secretion

A

GIP

  • Stimulus
    • fatty acids, amino acids, and oral glucose
  • secretin-glucagon family
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22
Q

Site of secretion of gastrin

A

G cells of the stomach

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23
Q

Site of secretion of CCK

A

I cells of duodenum and jejunum

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24
Q

Site of secretion of Secretin

A

S cells of duodenum

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25
Q

Site of secretion of GIP

A

Duodenum and jejunum

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26
Q

little gastrin have _______ amino acids

Big gastrin have _________- ammino acids

A

17

34

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27
Q

All biologic activity of gastrin resides in the____________

A

four C-terminal amino acids

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28
Q

Gastrin inncreases H secretion by gastric ___________ cells

A

parietal

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29
Q

Paatients with ________ have hypertrophy and hyperplasia of the gastric mucosa

A

gastrin secreting tumors

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30
Q

The most potent stimuli for gastrin secretion are _______ and ________

A

Phenylalanine and tryptophan

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31
Q

Vagal stimulation is mediated by ____________

A

gastrin releasing peptide

  • Atropine does not block vagally mediated gastrin secretion because the mediator of vagal effect is GRP, not ACh
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32
Q

Inhibitors of gastrin secretion

A

H+ in the lumen of the stomach

Somatostatin

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33
Q

Occurs when gastrin is secreted by non-B cell tumors of the pancreas

A

Zollinger-Ellison syndrome

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34
Q

Homologous to gastrin

A

CCK

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35
Q

the biologic activity of CCK resides in the _____________

A

C terminal hepatapeptide

  • 5 C-terminal amino acids are the same in CCK and Gastrin
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36
Q

T/F. triglycerides stimulate the release of CCK

A

false

they cannot cross intestinal membrane

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37
Q

homologous to glucacon

A

Secretin

  • 14 of the 27 amino acids in secretin are the same as those in glucagon
    • All of the amino acids are required for biologic activity
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38
Q

Homologous to secretin and glucagon

A

GIP

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39
Q

More effective in causing insulin release (ORAL/IV glucose)

A

oral

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40
Q

Candidate hormones

A

secreted by the GI tract

  • Motilin
    • increases GI motility and is involved in interdigestive myoelectric complexes
  • Pancreatic poypeptide
    • inhibits paancreatic secretion
  • GLP-1
    • bind to pancreatic B cells and stimulates insulin secretion
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41
Q

Released from endocrine cells in the GI mucosea

diffuse ofver short distances to act on target cells located in the GI tract

A

paracrines

  • Somatostatin
  • histamine
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42
Q

Secreted by cells throughout the GI tract in rsponse to H in the lumen. Its secretion is inhibited by vagal stimulation

inhibits the release of all GI hormones

inhibits gastric H secretion

A

Somatostatin

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43
Q

secreted by mast cells of the gastric mucosa

increases gastric H secretion directly and by potentiating the effects of gastrin and vagal stimualtion

A

Histamine

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44
Q

synthesied in neurons of the GI tract, moved by axonal transport down the axons, and released by action potential in the nerves

diffuses across the synaptic cleft to target ce;;s

A

Neurocrines

  • vasoactive intestinal peptide (VIP)
  • GRP (bombesin)
  • enkephalins
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45
Q

homologous to secretin

released from neurons in the mucosa and smooth muscle of the GI tract

relaxation of GI smooth muscle, including the LES

stimulates pancreatic HCO3 secretion and inhibits gastric H secretion

A

VIP

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46
Q

secreted by pancreatic islet cell tumors and is presumed to mediate pancreatic cholera

A

VIP

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47
Q

released from vagus nerbes that innervate the G cells

stimulates gastrin release from G cells

A

GRP (bombesin)

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48
Q

secreted from nerves in the mucosa and smooth muscle of the Gi tract

stimulates contraction of GI smooth muscles, particularly the LES, pyloric sphincter, and ileocecal sphincters

inhibit intestinal secretion of fluid and electrolytes

A

Enkephalins (met-enkephain and leu-enkephalin)

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49
Q

Hormone assciated with the use of opiates in the teatment of diarrhea

A

Enkephalins (met and leu)

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50
Q

satiety center

A

ventromedial nucleus of the hypothalamus

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51
Q

Feeding center

A

lateral hypothalamic area of the hypothalamus

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52
Q

Release proopiomelanocortin in the hypthalamic centers and cause decreased appetite

A

Anorexigenic neurons

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53
Q

release neuropeptide Y in the hypothalamic centers and stimulate appetite

A

Orexigenic neurons

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54
Q

secreted by fat cells. It stimulates anorixegic neurons and inhibts orexigenic neurons

A

Leptin

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55
Q

secreted by gastric cells. It stimulate orexigenic neurons and inhibits anorexigenic neuros, thus increasing appetie

A

ghrelin

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56
Q

Contractile tissue of the GI tract is almost exclusively ____________ with te exception of pharynx, upper one thir of esophagus, and external anal sphincter all of which are striated muscles

A

Unitary smooth muscle

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57
Q

Depolariation of the ____________ leads to contraction of a ring of smooth muscle and a decrease in diameter of the segment of the GI tract

A

circular muscle

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58
Q

occur in the lower esophagus, gastric antrum, and small intestine, which contract and relax periodically

A

Phasic contractions

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59
Q

Occur in the lower esophageal sphincter, orad stomac, and ileocecal and internal anal sphincters

A

Tonic contractions

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60
Q

slow waves are ___________ inherent to the smooth muscle cells of some parts of the GI tract

A

osclillating membrane potentials

  • occur spontaneously
  • originae in the intestitial cells of cajal
  • not action potentials although they determine the pattern of action of potentials
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61
Q

Mechanism of slow wave production

A
  • cyclic opening of calcium channels followed bu opening of K channels
  • Depolarization during each slow wave brings the membrane potential of smooth muscle cells closer to threshold and therefore increases the probability that action potentials will occur
  • Action potentials, produced on top of the background of slow waves then intitiate phaseic contractions of the smooth muscle cells
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62
Q

sets the maximum frequency of contractions for ach part of the GI tract

A

frequency of slow waves

  • lowest in the stomach
  • highest in the duoddenum
  • not influenced by neural or hormonal input
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63
Q

lubricates food by mixing it with saliva

decrease the sie of food particles to facilitate swallowing and to begin the digestive process

A

Chewing

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64
Q

The swallowing refelx is coordinated in the ___________

A

Medulla

  • fibers in the vagus and glossopharyngeal nerves carry information between the gI tract
  1. the nasopharynx closes and at the ame time, breathing is inhibited
  2. the laryngeal muscles contract to close the glottis and elevate the larynx
  3. peristalsis begins in the pharynx to propel the food bolus toward the esophagus. simultaneously, the upper esophageal sphincter relaxes to permit the food bolus to enter the esophagus
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65
Q

Because the esophagus is located in the thorax, intreaesophageal pressure equal thoracic pressure which is _______ than atospheric pressure.

A

lower

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66
Q

Esophageal motility

A
  1. the UES relaxes to permit swallowed food to enter te esophagus
  2. the upper esophageal sphincter then contracts so that food will not reflux nto the pharynx
  3. A primary peristaltic contraction creates an area of high pressure behind the food bolus.gravity accelerates movement
  4. A seconday peristaltic contraction clears the esophasugs of any remaining food
  5. The lower esophageal sphincter relaxes mediated vagally and the nuerotransmmitte is VIP
  6. the orad region of the stomach relaxes (“receptive relaxation”) to allow the food bolus to enter the stomach
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67
Q

may ccur if the tone of the lower esophageal sphincter is decreased and gastric ocntent reflux into the stomach

A

GERD

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68
Q

May occur if the lower esophageal sphincters dows not relax during swallowing and food accumulates in the esophagus

A

Achaalsia

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69
Q

Three layers of smooth muscle in the stomach

A
  • longitudinal
  • circular
  • oblique
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70
Q

Three anatomic regions of the stomach

A

fundus

body

antrum

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71
Q

The ______ of the stomach includes the fundus and the proximal body. This region contains oxyntic glands and is responsible for receiving the ingested meal

A

orad region

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72
Q

the _____ of the stomach includes the antrum and the distal body. This region is responsible for the conrations that mix food and propel it into the duodenu

A

Caudad

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73
Q

is a vasovagal refelx that is initiated by distension of the stomach and is abolished by vagotomy

A

receptive relaxation

  • the orad of the stomach relaxes
  • CCK paticipates by increasing distensibility of the orad stomach
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74
Q

Mixing and Digestion

A
  1. Slow waves in the caudad stomach occur at a frequency of 3-5 waves/min. they depolarize the smooth muscle cells
  2. If threshold is reached during the slowwaves, action potentials are fired, followed by contraction
  3. thus, the frequency of slow waves, action potentials are fired, followed by contraction. Thus, the frequency of slow waves sets the maximal frequency of contraction
  4. a wave of contraction closes the distal antrum, thus the caudad stomach contracts, food is propelled back into the stomach to be mixed (retropulsion)
  5. Gastric contraction are inceased by vagal stimulation and decreaed by sympathetic stimulation
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75
Q

Even during fasting, stomach contractions called____________ occure at 90 minute intervals and clear the stomach of residual food

A

Migrating myoelectric complex

  • Motilin is the mediator of these contractions
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76
Q

The rate if gastric emptying is fastest when the stomach contents are ________

A

Isotonic

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77
Q

_____ inhibits gastric emptying by stimulating the release of CCK

A

Fat

78
Q

_________in the duodenum inhibits gastric emptying via direct neural redlexes

A

H+

79
Q

Slow waves in the small intestine set the basic electrical rhythm, whic occurs at a frequency of

A

12 waves/min

80
Q

___________increases intetsinal smooth muscle contraction

A

parasympathetic stimualtion.

(sympathetic stimulation decreases it)

81
Q

mix the intestinal contents

a section of small intestine contracts sending the intestinal in both orad and caudad directions,

Back and forth segment causes mixing without any net forward movement of the chyme

A

Segmentation contractions

82
Q

are highly coordinated and propel the chyme through the small intestine toward the large instestine. Ideally, peristalsis occurs after digestion and absorption have taken place.

A

Peristaltic contractions

83
Q

Peristaltic reflex

A

Coordinated y the enteric nervous system

  1. Food in the intestinal lumen is sensed by enterochromaffin cells, which release serotonin (5-HT)
  2. 5-HT bind to receptors in intrinsic primary afferent neurons (IPANs), which initiate the peristaltic reflex
  3. Behind the food bolus, excitatory transmitters cause contraction of circular muscle and inhibitory transmitters cause relaxation of longituinal muslces, In front of the bous, inhibitory transmitters cause relaxation of circular muscle and excitatory transmitters cause contraction of longitdinal muscle
84
Q

mediated by extrinsic ANS and possibly gastrin

The presence of food in the stomach triggers increaed peristalsis in the ileum and relaxation of the ileocecal sphincter. As a result, the instestinal contents are delivered to the large intestine

A

Gastroileal reflex

85
Q

saclike segments, appear after contractions of large intestines

A

Haustra

86
Q

_________ in the proximal colon mix the contents and are responsible for the appearance of haustra

A

Segmentation contractions

87
Q

Mass movements occur _______/day and cause the colonic contents to move distally for long distances (from transverse colon to the sigmoid colon)

A

1 to 3

88
Q

Most colonic water absorption occurs in the ________

A

proximal colon

89
Q

As the rectum fill with fecal material, it contracts and the internal anal sphincter relaxes

A

Rectosphincteric reflex

90
Q

once the rectum is filled to about _______ of its capcity, there is an urger to defecate, However defecation is prevented because the _______ is tonically contracted

A

25%

external anal sphincter

91
Q

The presence of food in the stomach increases the motilit of the colon and increases the frequency of mass movements

A

gastrocolic reflex

92
Q

he gastrocolic has a rapid ________ component that is initiated when stomach is stretched by food

A

parasympathetic

93
Q

the absence of the colonic enteric nervous system, results in constriction of the involved segment, marked dilatation and accumulation of intestinal cintents proximal to the constriction and severe constipation

A

Hirschprung disesase

94
Q

The vomiting ceter in the ________is stimuated by tickling the back of throat, hastric distention and vestibualr stimulation (motion sickness)

A

medulla

95
Q

The chemorecptor trigger zone in the __________ is activated by emetics, radiation, and vestibular stimulation

A

fourth ventricle

96
Q

Summary of GI secretions

A
97
Q

Functions of Saliva

A
  • Initial starch digestion by a-amlase adn initial triglyceride digestion by lingual lipase
  • Lubrication
  • Protection
98
Q

Characteristiccs of saliva

A
  • High volume
  • High K and HCO3
  • Low Na and Cl
  • Hypotonicity
  • presence of a-amylase, lingual lipase and kallikrein
99
Q

The composition of salivea varies with the _________

A

salivary flow rate

  • The lowest flow rate
    • lowest osmolarity
    • lowest Na, Cl and HCO3
    • Highest K concenration
  • highest flow rate: (Up to 4 ml/min)
    • closest to that of plasma
100
Q

Saliva is formed by three major glands

A

parotid

submandibular

sublingual

101
Q

Produces an initial salive with a composition similar to plasma

this initial plasma is isotonic

A

Acinus

102
Q

The ducts modify the initial saliva by ______-

A
  • Reabsorption of Na and Cl
  • Secretes K and HCO3
  • Aldoseterone acts on the ductal cells to increase reabsorption of sodium and the secretion of potassium
  • saliva becomes hypotonic in the ductsbecause the ducts are relatively impermeable to water.
  • the effect of flow rate on saliva composition is explained primarily by changes in the contact time available for reabsorption
103
Q

Saliva production is controlled by ____________

A

parasympatehtic and sympatheic

(not GI hormones)

104
Q

Salivar production is unique that it is increased by _____________________

A

BOTH PNS ans SNS

105
Q

Increases saliva production by increasing transport porcesses in the acinar and ductal cells and by causing vasodilaton

A

parasympathetic stimulation (CN VII and IX)

106
Q

Cholinergic receptors on acinar cells and ductal cells are ____________—

A

muscarinic

107
Q

The second messengar in parasympathethic stimualtion of salivary production is __________

A

Inositol 1,4,5 triphosphate (IP3)

and

Increased intracellular calcium

  • Atropine innhibit the production of saliva and cause dry mouth
108
Q

Inreases the production of saliva and the growth of salivary glands.

A

Sympathetic stimulation (effects are smaller than those of parasympathetic)

109
Q

Receptors on acinar and ductal cells are ________

A

B-adrenergic

110
Q

The second messenger on sympathetic stimulation of production of saliva is ____________

A

cyclic adenosine monophasphate

111
Q

Parietal cells secretes ________ and are found in ________

A

HCl and Intrinsic factor

Fundus of stomach

  • stimulus
    • gastrin
    • vagal stimulation (ACh)
    • Histamine
112
Q

Chief cells secretes _______________ and are ound in the ____________

A

Pepsinogen (converted to pepsin at low pH)

Body (fundus)

  • Stimulus
    • Vagal stimualtion (ACh)
113
Q

G cells secretes ________ found in the__________

A

Gastrin

antrum

  • Simulus
    • Vagal stimulation (via GRP)
    • small peptides
    • inhibited by somatostatin
    • inhibited by H in stomah (via stimulation of somatostatin release)
114
Q

Mucous cells secretes ___________ found in the __________

A

Mucus, pepsinogen

  • Stimulation
    • Vagal stimulation (ACh)
115
Q

Mechanism of gastric H+ secretion

A
  • Parietal cells secrete HCl into the lumen of the stomach, and concurrently absorbs HCO3 into the bloodstream
  1. In the parietal cells, CO2 and H2O are converted to H and HCO3 catalyzed by carbonic anhydrase
  2. H+ is secreted into the lumen of the stomach by the H+-K pump (H-K-ATPase). Cl is secreted along with H, thus the secretion product is HCl
  3. The HCO3 produced in the cells is absorbed into the bloodstream in exhange for Cl (Cl-HCO3 exchange). As HCO3 is added to the venous blood, the pH of the blood increases (Alkaline tide).
116
Q

Omeprazole inhibits the _______ and __________

A

H,K ATPase and Blocks H+ secretion

117
Q

If vomiing occurs, gastric H+ never arrives in the small intestine, there is no stimulus for pancreatic HCO3 secretion, and the arterial blood _____________

A

metabolic alakalosis

118
Q

Increases H+ secretion by direct pathway and indirect pathway

A

Vagal stimulation

  • Direct pathway
    • The vagus nerve innervates parietal cells and stilmulates H+ secretion
    • ACh
    • Muscarinic receptors
    • 2nd messenger : IP3 and Increased intracellular Ca
  • Indirect pathway
    • vagus nerves innervates the G cells and stimulates gastric secretion, which then stimulates H+ secretion by an endocrine action.
    • Neurotransmitter : GRP
119
Q

Cholinergic muscarinic antagonist, inhibits H+ secretion by blocking the direct pathway, which uses ACh

A

Atropine

  • does not block H secretion completely because it does not inhibit the indirect pathway, which causes GRP as neurotransmitter
120
Q

__________elimates both direct and indirect pathway

A

Vagotomy

121
Q

released in response to eating a meal

stimulates H+ secretion by interacting with CCKb receptor on the parietal cells

also stimulates enterochromaffin-like cells and histamine secretion

A

gastrin

122
Q

The second messenger for gastrin in the parietal cells

A

IP3/Ca

123
Q

Released from ECL cells in the gastric mucosa and diffuses to the nearby parietal cells

stimualtes H secretion by activating H2 receptors on the parietal cell membrane

A

Histamine

  • The H2 receptor is coupled to adenylyl cyclase via Gs protein
124
Q

Second messenger for histamine

A

cAMP

125
Q

H2 receptor blocking drugs suc as cimetiine,_______________

A

inhibit secretion of H+ by blocking the stimulatory effect of histamine

126
Q

Histamine potentiates the actions of _____ and _______ in stimulating H+ secretion

A

ACh and gastrin

127
Q

ACh potentiates the action of _______ and ______ in stimulatng H+ secretion

A

Histamine and gastrin

128
Q

Inhibition of gastric H+ secretion

A
  • negative feedback
  1. low pH (<3 in the stomach)
  2. somatostatin
    • direct and indirect pathway
  3. Prostaglandin
129
Q

Somatostatin inhibits gastric H+ secretion via direct pathway through _____________

A

binding to receptors on the parietal cells that are coupled to adenyly cyclase via Gi protein - > decreasing cAMP

130
Q

Somatostatin inhibits gastric H+ secretion via indirect pathway through _____________

A

inhibiting release of histamine and gastrin

131
Q

Prostaglandin inhibits gastric H+ secretion by ______________-

A

activating Gi protein, inhibiting adenyly cyclase and decreasing cAMP levels

132
Q

Gastric ulcers

A
  • gastric mucosa is damaged
  • Gastric H+ secresion is decreased
  • Gastrin levels are increased
  • H. pylori colonizes the gastric mucus and releases cytotoxins that damage the gastric mucosa
  • H. pylori contans urease, which converts urea to NH3
133
Q

Diagnostic tests for H. pylori involves________–

A

drinking a solution of 13C- urea which is convertedd to 13CO2 by urease and measured in the expired air

134
Q

Duodenal ulcers

A

duodenal mucosa is damaged

Gastric H+ secretion is increased. Excess H+ is delivered to the duodenum, damaging the duodenal mucosa

Gastrin secretion in response to a meal is increased

H. pylori is also a major cause of duodenal ulcer. H. pylori inhibits somatostain secretion and inhibits intestinal HCO3 secretion

135
Q

Zollinger-Ellison syndrome

A

Occurs when a gastrin-secreting tumor of the pancrease causes increased H+ secretion

H+ secretion continues unabated because the gastrin secreted by pancreatic tumor calls is not subject to negative inhibition by H+

136
Q

Contains a high concentration of HCO3, whose purpose is to neutralize the acidic chyme that reaches the duodenum

contains enymes essential for the digestion of protein, carnihydrate, and fat

A

Pancreatic secretion

137
Q

Pancreatic juice is characterized by

A
  • high volume
  • virually the same Na and K concentrations as plasma
  • Much higher HCO3 concentration than plasma
  • much lower Cl concentraton than plasma
  • sotonicity
  • Pancreatic lipase, amylase, and proteases
138
Q

The composition of tthe aqueous component of pancreatic secretion varies with the ________

A

flow rate

  • at low rates
    • isotonicc fluid (Na and Cl)
  • at highrates
    • isotonic fluid (Na and HCO3)
139
Q

Pancreatic struccture that produce a small volume of initial pancreatic secretion, which is mainly Na and Cl

A

Acinar

140
Q

Pancreatic structure that modify the initial pancreatic secretion bys ecreting HCO3 and absorbing Cl via a Cl-HCO3 exchange mechanism in the membrane

A

Ductal cells

141
Q

secreted by S cells of the duodenum in response to H+ in the duodenal lumen

actis on the pancreatic duct cells to increase HCO3 secretion

A

Secretin

142
Q

the second messenger of secretin is __________

A

cAMP

143
Q

secreted by the I cells of the duodenum in response to small peptides, amino acids, and fatty acids in the duodenal lumen

acts on the pancreatic acinar cells to incease enzyme secretion

A

CCK

  • potentiates the effect of secretin on ductal cells to stimulate HCO3 secretion
144
Q

the second messengers of CCK are_________

A

IP3 and increased intracellualr Calcium

145
Q

Reeased in response to H+, small peptides, amino acids, and fatty acids in the duodenal lumen

stimulates enzyme secretion by the acinar cells and like, CCK potentiates the effect of secretin on HCO3 secretion

A

ACh (via vagovagal reflexes)

146
Q

disorder of pancreatic secretions

results from adefect in Cl channels that is caused by a mutation in the cysticfibrosis transmembrane conductance regualtor (CFTR) gene

associated with a deficiency of pancreatic enzymes resulting in malabsorption and steatorrhea

A

Cystic fibrosis

147
Q

Composition of bi;e

A

bile salts, phospholipids, cholesterol, and bile pigments

148
Q

____are ampipathic molecules. they orient themselves around droplets of lipid and keep the lipid droplets dispersed

A

Bile salts

  • aid in the intestinal digestion and absorption of lipds by empulsifying and solubilizing them in micelles
149
Q

Bile is produced continuoysly by ________

A

hepatocytes

150
Q

_________ increase the foration of bile

A

Choleretic agents

151
Q

Bile formation

A
  1. Primary bile acids (cholic acid and chenodeoxycholic acid) are synthesized from cholesterol by hepatocyes
    • In the instestine, bacteria convert a portion of each of the primary bileacids to secondary bile acids (deoxycholic acid and lithoholic acid)
  2. Bile acids are conjugated with glycine or taurine to form their respective bile salts
  3. Electrlytes and water are added to the bile
  4. Bile is concentrated in the gallbladder as a rsult if isosmotic absorption of solutes and H2O
152
Q

released in response to small peptides and fatty acids in the duodenum

tells the gallbladder that bile is needed to emulsify and absorb lipids in the duodenum

causes contraction of the gallbladder and relaxation of sphincter of Oddi

A

CCK

153
Q

the terminal ileum contains _________, which is a secondary active transporte that recircualtes bile acids to the liver

A

Na-Bile acid contransporter

  • because bile acids are not recirculated until thery reach the terminal ileum, bile acids are present for maximal absorption of lipids throughy the upper small intestine
154
Q

the surface area for absorption in the small intestine is greatly incrased by the presene of the _________

A

brush border

155
Q

Mechanism of Carbohydrate absorption

A

Na-dependendent cotransport (glucose, galactose)

Facilitated diffusion (fructose)

  • small intestine
156
Q

Mechanism of absorprion of proteins

A

Na-dependent contransport (amino acids)

H+ dependent cotransport (di and tripeptides)

  • small intestine
157
Q

Mechanism of absorption of Lipids

A

Micelles form with bile salts in intestinal lumen

Diffusion of fatty acids, monoglycerides, and cholesterol into cell

Re-esterification in cell to triglycerides and phospholipids

Chylomcirons form in cell (requires apoprotein) and are transfered to lymph

  • Small intestine
158
Q

Mechanism of absortption of fat soluble vitamins

A

Micelles with bile salts

159
Q

Mechanism of absorption of water-soluble vitamins

(Vit. B12)

A

Na-dependent cotransport

Intrinsic factor-vitamin B12 complex

  • Small intestine, ileum of small intestine
160
Q

Mechanism of absortpion of bile acids

A

Na-dependent contransport

recirculated to liver

  • Ileum of small intestine
161
Q

mechanism of absorption of Calcium

A

Vit. D dependent (calbindin D-28K)

162
Q

Mechanism of absorption of Fe2+

A

Binds to apoferritin in cell

circulates in blood bound to transferrin

  • Small inetstine
163
Q

only __________- are absorbed CHO.

A

monosaccharides

164
Q

hydroyze 1,4 glycosidic bonds in starch, yieldng maltose, maltotriose, and a-limit dextrins

A

a-amylase

165
Q

_______, _____ and_______ in the intestinal brush border then hydrolyze the oligosaccharids to glucose

A

maltase

a-dextrinase

sucrase

166
Q

Results from the absence of brush border lactase and thus the inability to hydorlyze lactcose to glucose and galactose for absorption,

A

lactose intolerance

  • Osmotic diarrhea
167
Q

______ degrade proteins by hyrdolyzing interior peptide bonds

A

Endopeptidases

168
Q

______ hydrolyze on amino acid at a time from the C terminus of proteins and peptides

A

Exopeptidases

169
Q

Not essential for protein digestion

secreted as pepsinogen by the chief cells of the stomach

A

Pepsin

170
Q

The optimum pH for pepsin is __________

A

between 1 and 3

171
Q

Pancreatic proteases

A

Includes, trypsin chymotrypsin, elastase, caboxypeptidase A, and Carboxypeptidase B

Secreted in ananctive forms

172
Q

Trypsinogen is activated to trypsin by a brush border enzyme

A

Enterokinase

173
Q

Digestive products of protein can be absorbrd as ______,_______. and _______

A

Amino acids, dipeptides, and tripeptides

174
Q

Free amino acids are absorbed via

A

Na-dependent amino acid cotransport in the luminal membrane. (analogous to the cotransporter for glucose and galactose)

  • four separate carrirs
    • neutral
    • acidic
    • basic
    • imino
175
Q

faster absorption (dipeptides and tripeptides or amino acids)?

A

Dipeptides and tripeptides

  • via H-dependent cotransport
176
Q

CCK ______ gastric emptying

A

Slows

177
Q

In the intestinal cells, the product of lipid digestion are _______ to triglcyerides, cholesterol ester, and phospholipid and with apoproteins form Chylomicrons

A

re-esterified

178
Q

Chylomicrons are transported out of the intestinal cells by ___________

A

exocytosis

179
Q

Malabsorption of lipid - steatorrhea can be caused by ___________

A
  • Pancreatic disease
  • Hypersecretion of gastrin
    • low duodenal pH inanctivates pancreatic lipase
  • Ileal resection
    • depletion of the bile acid pool
  • bacterial overgrowth
    • deconjugation of bile acids and their early absorption in the upper small instestine
  • Decreased number of intestinal cells for lipid absorption (tropical sprue)
  • Failure to synthesize apoprotein B
180
Q

_________ attach the epithelial cells to one another at the luminal membrane

A

Tight junctions

181
Q

Absorption of NaCl

A
  1. Na moves into the intestinal cells, across the luminal membrane, and down its gradient.
    • Passive diffusion
    • Na-glucose or Na-amino acid cotransport
    • Na-Cl cotransport
    • Na-H exchange
  2. Na is pumped out of the cell against its gradient by the Na-K pump in the basolateral membranes
  3. Cl absorption accompanies Na absorption throghout the GI tract by
    • Passive diffusion by a paracellular route
    • Na-Cl cotransport
    • Cl-HCO3 exchange
182
Q

Absorption and secretion of K

A
  • Dietary K is absorbed in the small intestine by passive diffusion via a paracellular route
  • K is actively secreted in the colon by a mechanism similar to that for K secretion in the renal distal tubule
    • Aldosterone
183
Q

Absorption of water

A
  • Secondary to solute absorption
  • isosmotic in the small intestine and gallbladder. the emchanism for coupling solute and water absorption in these epithelia is the same as that in the renal proximal tubule
  • In th colon, water permeability is much lower than in the small intestine, and feces may be hypertonic
184
Q

The secretory mechanisms of electrolytes and water by the intestine are located in the_________

A

crypts

185
Q

________ is the primary ion secreted into the intestinal lumen

A

Chloride

  • transported through Cl channels in the luminal membrnae that are regulated by cAMP
186
Q

Sodum is secreted into the lumen by ___________

A

passively following Cl

187
Q

Causes diarrhea by stimulating Cl secretion

A

Vibrio cholerae

  • cholera toxin catalyzes ADP ribosylation of the a-subunit of the Gs protein coupled to adenylyl cyclase
  • Intracellualr cAMP increases, as aresult, Cl channels in the luminal membrane open
  • Na and water follows Cl and lead to secretory diarrhea
188
Q

Hemogloin is degraded to ________ by the RES

A

bilirubin

189
Q

bilirubin is carried in the circulation bound to ___________

A

albumin

190
Q

In the liver, bilirubin is conjugated with glucuronic acid via the enzyme ____________

A

UDP glucuronyl transferase

191
Q

Phase I reactions are catalyzed by

A

cytochrome P450 enzymes

BRS (PHYSIO) (14 decks)

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