Intro to GI (1)

Question 1

How many calories a day does a sedentary adult require?

Answer 1

30 kcal/kg body weight per day

Question 2

Which sphincter has the highest resting pressure?

Answer 2

UES

Question 3

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

Answer 3

striated muscle

prevents air from entering esophagus

Question 4

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

Answer 4

smooth muscle

prevents reflux of gastric contents into esophagus

Question 5

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

Answer 5

duodenum and stomach

regulates gastric emptying and prevents duodenal reflux

Question 6

What does IBS entail?

Answer 6

overgrowth of bacteria in the small intestine

Question 7

What sphincter is incompetent in heartburn?

Answer 7

LES

GERD

Question 8

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

Answer 8

internal - smooth muscle

external - skeletal muscle

Question 9

Describe the fluid shifts during digestion?

Answer 9

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

we only excrete 100-200 mL in feces

Question 10

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

Answer 10

1-2

parietal cells

Question 11

How is the pH neutralized in the duodenum?

Answer 11

pancreas excretes bicarbonate

Question 12

Myenteric (auerbach’s plexus)

1. btwn what two layers?
2. extends from where to where
3. function

Answer 12

1. btwn longitudinal and circular
2. extends from proximal end of esophagus to rectum
3. peristalsis

Question 13

Submucosal (meissener’s) plexus:

1. btwn what two layers?
2. extends from where to where?
3. function

Answer 13

1. btwn circular and submucosal
2. in small and large intestines
3. controls secretion, absorption, cntrxn
   affects local infolding of mucosa

Question 14

What layer of the small intestine is responsible for infolding ?

Answer 14

muscularis mucosae

Question 15

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

Answer 15

NO0O..able to function independently

- does receive input however

Question 16

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

Answer 16

the great and wonderful gut

Question 17

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

Answer 17

1. mechanoreceptors
2. chemoreceptors
3. osmoreceptors

Question 18

What is the PNS affect on the GI system?

Answer 18

inc motility and relaxation of sphincters

Question 19

What NTs does the PNS use?

Answer 19

ACh for postganglionic cells

some use peptides too

Question 20

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

Answer 20

vagus - proximal 2/3 from pharynx to distal colon

pelvic- distal 2/3

Question 21

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

Answer 21

NE

Question 22

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

Answer 22

CN 7 and 9

Question 23

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

Answer 23

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

Question 24

What does CN10 induce during the intestinal phase?

Answer 24

pancreatic enzyme production and buffer secretion

Question 25

What regulates primary peristalsis?

Answer 25

CN10 through the medulla and vagus swallowing center

Question 26

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

Answer 26

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

Question 27

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

Answer 27

When spike potentials reach threshold: 40 mv | Ca2+ rushes in through L type channels

Question 28

What AP lasts longer, nerve or gut?

Answer 28

gut -->10-40 times longer

Question 29

Where is slow wave frequency the highest? the slowest?

Answer 29

highest - small intestine: 12/min | slowest - stomach: 3/min

Question 30

What modulates the production of APs in the gut?

Answer 30

neural and hormonal output

Question 31

What is the effect of atropine on the gut?

Answer 31

weak peristalsis

Question 32

What direction does peristalsis conduct food?

Answer 32

aboral - orad to caudad

Question 33

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

Answer 33

3-5 hours

Question 34

What is the function of the gastroenteric reflex?

Answer 34

enhances peristaltic motility and secretions

Question 35

What is the function of the gastroileal reflex?

Answer 35

opening of ileocecal valve to permit passage

Question 36

What is the function of the enterogastric reflex?

Answer 36

decreases gastric motility and secretions | -stim cntrxn of pyloric sphincter to inhibit backflow

Question 37

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

Answer 37

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)

Question 38

What neurons control the circular and longitudinal muscles?

Answer 38

circular- inhibitory and excitatory longitudinal - excitatory

Question 39

How does a pathological ileus differ from physiological ileus?

Answer 39

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

Question 40

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

Answer 40

during fasting: 1. quiescence 2. little activity 3. strong activity

Question 41

What is the function of the MMC?

Answer 41

sweep the stomach and small intestine of residue

Question 42

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

Answer 42

pyloric sphincter is inhibited | particles larger than 2 mm can pass into duodenum

Question 43

When and where is the MMC occuring?

Answer 43

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

Question 44

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

Answer 44

motilin - secreted from duodenal Mo cells | -acts through ENS and ANS

Question 45

What are bezoars?

Answer 45

indigestible material that accumulates if the MMC does not occur

Question 46

How would a vagotomy affect the MMC?

Answer 46

it would reduce contractile activity

Question 47

What is the voluntary stage of swallowing?

Answer 47

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

Question 48

What is the involuntary pharynx phase of swallowing?

Answer 48

soft palate blocks nasopharynx epiglottis blocks trachea relaxation of UES

Question 49

What is the involuntary esophageal phase of swallowing?

Answer 49

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

Question 50

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

Answer 50

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

Question 51

What is accomodation in the stomach?

Answer 51

increase in volume without inc in pressure

Question 52

What can cause disorders of swallowing?

Answer 52

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

Question 53

What regulates receptive regulation in the LES and fundus ?

Answer 53

postganglionic vagal fibers that release VIP

Question 54

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

Answer 54

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

Question 55

What is gastric emptying mediated by?

Answer 55

combo of neural and hormonal signals | vagus nerve, secretin, CCK, GIP

Question 56

What is achalasia?

Answer 56

failure of the LES to relax during swallowing | -buildup of food in esophagus

Question 57

What is the proximal gastric reservoir?

Answer 57

fundus and 1/3 of body - continuous contractile tone - accomodation - compressive force on contents

Question 58

What is the distal antral pump?

Answer 58

caudal 2/3 of body, antrum, pyloris | propels chyme towards GD junction

Question 59

What layers of muscle does the stomach have?

Answer 59

longitudinal, circular, oblique

Question 60

Describe churning in the stomach?

Answer 60

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