Motility Of Gi Tract

Front 1

increased motility = _____ transit time

Back 1

decreased

Front 2

what are the three functions of GI motility?

Back 2

ingestion and breakdown, transport, and waste removal (of digested, unabsorbed and secreted)

Front 3

contraction of smooth muscle layers results in _______ GI motility actions

Back 3

increased

Front 4

relaxation results in ______ GI motility actions.

Back 4

decreased

Front 5

what 2 actions does the basic pattern of muscle contractile activity alternate between?

Back 5

segmentation and peristalsis

Front 6

what causes the action of segmentation?

Back 6

focal contraction of the circular muscle layer

Front 7

what is the end result of segmentation?

Back 7

reduction of food particle size, homogenized particles with digestive enzymes, and exposed material to mucosal surface.

Front 8

T/F
Segementation does not result in significant net movement of material along the tract.

Back 8

TRUE!

Front 9

what is the action of peristalsis? (circular muscle, longitudinal muscle)

Back 9

contraction of a circular muscle behind the food mass, followed by relaxation of a circular muscle and contraction of a longitudinal muscle ahead of food mass and then contraction of a circular muscle behind the food mass.

Front 10

T/F
Peristalsis is a bidirectional action.

Back 10

FALSE:
unidirectional

Front 11

what stimulates peristalsis?

Back 11

a bolus of foodstuff in the lumen

Front 12

in a peristalsis reflex, what stimulates the afferent enteric neurons? with what do these sensory neurons synapse?

Back 12

mechanical distension and mucosal irritation. two sets of cholinergic interneurons

Front 13

what are the actions of the two sets of cholinergic interneurons?

Back 13

one set: activates excitatory motor neurons ABOVE the bolus (containing Ach and substance P)--> stimulate contraction of smooth muscle above the bolus.
second set: activates inhibitory motor neurons that cause relaxation of smooth muscle below the bolus (NO, VIP, and ATP)

Front 14

Increased parasympathetic = _____ motility; Increased sympathetic = ______ motility

Back 14

increased; decreased

Front 15

what is the intrinsic control by the enteric NS responsible for?

Back 15

primarily myenteric plexus as well as coordination of local and inter-regional control.

Front 16

what are the four ways in which GI motility is regulated?

Back 16

extrinsic autonomic, intrinsic, myogenic and humoral

Front 17

what are the 7 GI sphincters?

Back 17

upper esophageal, lower esophageal pyloric, ileocecal, colorectal, internal anal, and external anal

Front 18

what is the effect of relaxation and contraction on GI motility in the GI sphincters?

Back 18

relaxation increases GI motility; contraction decreases GI motility.

Front 19

what are the five jobs of the teeth and tongue?

Back 19

size reduction, mixing, propulsion, taste, and protection

Front 20

what affect does the introduction of a bolus of food in the mouth have on the muscles of mastication?

Back 20

first it initiates reflex inhibition of the muscle of mastication allowing the lower jaw to drop. That drop in turn initiates a stretch reflex of the jaw muscles that leads to rebound contraction.

Front 21

what are two stages of the swallowing process?

Back 21

voluntary and involuntary

Front 22

how long does the pharyngeal stage last? esophageal? and what kind of stage are these?

Back 22

pharyngeal = 6 sec; esophageal: 8-10 sec; and its the involuntary stage

Front 23

what initiates the voluntary stage of swallowing?

Back 23

by abroad propulsion of material into the oropharynx primarily by movements of the tongue

Front 24

what signifies the end of the voluntary stage?

Back 24

the food bolus sliding towards the pharynx

Front 25

what stimulates the pharyngeal stage?

Back 25

epithelial receptor in pharynx

Front 26

what are the steps involved in the pharyngeal stage?

Back 26

nasopharynx closes (via contraction of pharyngeal muscles), trachae closes, and respiration is inhibited.

Front 27

when does the esophageal stage begin?

Back 27

as the upper esophageal sphincter opens

Front 28

In what stage has all of the food emptied into the stomach?

Back 28

esophageal

Front 29

what determines the propulsion of ingested foodstuff?

Back 29

peristalsis and gravity

Front 30

Between swallowing, why are both the UES and LES under tonic contraction?

Back 30

to produce greater pressure than their adjacent compartents

Front 31

when does the UES constrict?

Back 31

once the bolus passes to prevent further air reflux

Front 32

during swallowing, where is peristalsis within the esophagus body initiated? why?

Back 32

just below the UES to move the food bolus toward the stomach

Front 33

when does the LES relax? what is this type of relaxation called?

Back 33

shortly before the peristaltic wave arrives. Receptive relaxation.

Front 34

what is primary peristalsis?

Back 34

a propulsive aborad contractile wave within the esophagus that is initiated through pharyngeal receptor contact (swallowing)

Front 35

wwhat controls the primary peristalsis?

Back 35

vagus nerves in connection with the esophageal myenteric plexus.

Front 36

what is the function of primary peristalsis?

Back 36

functions to propel newly entering boluses to stomach

Front 37

what initiates secondary peristalsis?

Back 37

distention of the esophagus

Front 38

what controls secondary peristalsis?

Back 38

partly controlled by both intrinsic (myenteric and extrinsic NS)

Front 39

what is the function of secondary peristalsis?

Back 39

to clear or sweep the esophagus of residual food particles remaining after primary peristaltic wave or to remove gastric reflux

Front 40

what regulates esophageal body peristalsis?

Back 40

vagus nerve innervating striated and smooth muscle layers.

Front 41

T/F
enteric neurons can coordinate peristalsis independent of extrinsic innervation.

Back 41

TRUE!

Front 42

what maintains tonic closures in the UES? LES?

Back 42

UES: constituitive pharyngeal muscle tone
LES: intrinsic myogenic control

Front 43

what initiates relaxation in the LES during swallowing?

Back 43

vagus inhibitory reflex integrated via enteric neurons

Front 44

what regulates relaxation in the UES during swallowing?

Back 44

central inhibitory reflex between vagus and swallowing center that relaxes pharyngeal muscles.

Front 45

name this disorder:
Loss of LES relaxation in response to swallowing, loss of a peristalsis of the esophagus, elevated resting LES and intraesophageal pressures, and functional obstruction and progressive esophageal dilation, stasis of food.

Back 45

achalasia

Front 46

name the disorder.
>20% of swallows result in simultaneous contractions. may have multipeaked and.or prolonged contractions. Amplitude of the contractions may be increased, normal or decreased.

Back 46

diffuse esophageal spasm.

Front 47

name the disorder:
Peristaltic contractions of increased amplitude (>180mmHg) and/or increased duration (>8 sec)

Back 47

hypertensive peristalsis (nutcracker esophagus)

Front 48

name the disorder:
increased resting LES pressure (>40 mmHg above intragastric pressure)

Back 48

hypertensive LES

Front 49

name the disorder:
decreased amplitude (<30 mmHG) peristaltic or nonperistaltic contractions in distal esophagus. With or without hypotensive LES.

Back 49

hypotensive peristaltic contractions (ineffective peristalsis)

Front 50

name the disorder: LES pressure <10 mmHG. Increased frequency of transient lower LES relaxation.

Back 50

Hypotensive LES.

Front 51

what usually causes achalasia?

Back 51

degeneration of the postganglionic inhibitory neurons (NO/VIP) in the myenteric plexus

Front 52

what is the function of the orad portion of the stomach?

Back 52

storage of ingested food

Front 53

what is the function of the caudad portion of the stomach?

Back 53

mixing and emptying

Front 54

what are the three functions of the stomach?

Back 54

volume accommodation (storage of food until the food can be processed), mixing gastric contents and gastric emptying

Front 55

what type of pressure is maintained during eating to minimize gastric reflux into the esophagus?

Back 55

low intragastric pressure

Front 56

where are concentric circles of the food formed?

Back 56

in the orad portion of the stomach

Front 57

what is the purpose of the vagovagal reflex?

Back 57

to reduce the tone in the muscular wall of the body of the stomach.

Front 58

what does food initiate in the stomach?

Back 58

vagovagal reflex

Front 59

what is the major regulatory mechanism of volume accommodation?

Back 59

autonomic NS

Front 60

what initiates the Vagal reflex?

Back 60

the lower esophagus in response to swalloing.

Front 61

what are the GI hormones that increase gastric distensibility during the gastric phase of digestion?

Back 61

CCK and gastrin

Front 62

Mixing waves are ______ peristaltic ocnstrictor waves that are controlled by the ______

Back 62

weak; BER (electrical slow waves)

Front 63

what controls the amount of food that leaves the stomach during gastric emptying?

Back 63

muscle contractions of the antrum

Front 64

The amount of food emptied from the stomach depends on what two things?

Back 64

the peristaltic wave and pressure gradient between the antrum and duodenum.

Front 65

what affect does parasympathetic stimulation have on the contractile frequence, force and duration of contractions? sympathetic?

Back 65

para: increases; symp: decreases

Front 66

what hormone increases contraction of the caudad stomach?

Back 66

motilin

Front 67

what two hormones suppress motility?

Back 67

somatostatin

Front 68

the rate of emptying of isotonic, non-caloric fluids is proportional to what?

Back 68

the volume or distension of stomach

Front 69

T/F
hypertonic fluids empty faster than isotonic fluids.

Back 69

FALSE
both hypertonic and hypotonic fluid empty more slowly than isotonic fluid due to neural and hormonal factors.

Front 70

which organ regulates the delivery of calories?

Back 70

duodenum

Front 71

what effect does pH have on empting rate?

Back 71

as the pH decreases so does the rate.

Front 72

the _____ the antral peristalsis and intragastric pressure, the _______ the emptying

Back 72

greater; faster

Front 73

how does the duodenum control emptying?

Back 73

mediated by neural and humoral factors activated by nutrients

Front 74

what does a "too slow" gastric emptying stimulate?

Back 74

excess gastric acid secretion

Front 75

what occurs when the gastric emptying occurs too rapidly?

Back 75

the digestive and absorptive capacity of the small intestine is overwhelmed and fails to fully buffer acidic chyme.

Front 76

what is the transit time through the small intestine for chyme?

Back 76

2-4 hrs

Front 77

what do digestion and absorption of food depend on?

Back 77

motility

Front 78

what determines the frequency patterns of the contraction of the small intestine?

Back 78

intestinal slow waves

Front 79

which slow wave frequency is higher intestinal or gastric BER?

Back 79

intestinal

Front 80

what makes the intestinal BER different from gastric BER?

Back 80

frequency is higher in intestinal BER and the frequency decreases distally whereas the gastric BER has constant frequency

Front 81

why does the frequency of the intestinal BER decrease distally?

Back 81

to slow propulsion of intestinal contents into the colon.

Front 82

T/F
In segmentation, intestinal contents are compressed and propelled bidirectionally.

Back 82

TRUE!
successive contractions produce back and forth movement.

Front 83

T/F
during segmentation, the intestinal contents have a small net propulsion.

Back 83

FALSE....
there is no net propulsion during segmentation.

Front 84

when does segmentation predominately occur? why?

Back 84

after eating a meal (postprandially). To facilitate homogenization, circulation, and reduction of ingested material.

Front 85

T/F
Peristalsis can propel its contents for a long distance.

Back 85

FALSE
short distances (1-4cm)

Front 86

when does the ileocecal valve close?

Back 86

when colon pressure pushes fecal contents backward.

Front 87

what is function of the ileocecal valve? sphincter?

Back 87

valve: prevent fecal reflux into ileum; sphincter: controls ileal emptying rate

Front 88

if the ileal is distended, what happens to the sphincter tone and the motility rate?

Back 88

decreases sphincter tone and speeds motility rate

Front 89

if the colon is distended, what happens to the sphincter tone and the motility rate?

Back 89

sphincter tone is increased and motility rate is slowed.

Front 90

T/F
the frequency of the BER is independent of extrinsic inputs.

Back 90

TRUE!

Front 91

what affect does parasympathetic input have on the action potentials in the small intestine? sympathetic?

Back 91

increases; decreases

Front 92

what are the humoral controls that inhibit small intestine motility?

Back 92

epi, VIP, NO, secretin and glucagon

Front 93

what are the humoral controls that stimulate small intestine motility?

Back 93

gastrin, CCK, insulin, motilin, and serotonin

Front 94

what activates the enterogastric reflex in the small intestine?

Back 94

intestinal receptors sensitive to hydrogen ion, distension, and changes in osmolarity

Front 95

what controls the peristalsis and segmentation reflexes in the small intestine?

Back 95

enteric NS

Front 96

what is the purpose of the enterogastric reflex in the small intestine?

Back 96

it decreases gastric motility and slows the rate of gastric emptying, protecting the intestine from excessive acidity.

Front 97

what are the five reflexes of the small intestine?

Back 97

peristalsis, segmentation, enterogastric, ileocecal, and gastroileal.

Front 98

what is the function of the ileocecal reflex?

Back 98

increases motility of the ileum and relaxes the ileocecal sphincter, allowing chyme to pass from the ileum to the cecum.

Front 99

what is the function of the gastroileal reflex?

Back 99

increases ileal motility and movement through the ileocecal sphincter.

Front 100

what is the motility disorder of the small intestine?

Back 100

vomiting

Front 101

where is the vomiting center?

Back 101

medulla

Front 102

what are some of the complications of vomiting?

Back 102

loss of gastric contents, metabolic alkalosis and hypokalemia, loss of small intestine content, nutritional deficiency, ulceration, weakening of UES and LES.

Front 103

what is colonic motility important for?

Back 103

mixing of material for mucosal absorption, propulsion of contents from the ileum to the rectum to the anal canal, storage of feces and evacuation of waste.

Front 104

what is the most common motility action in the large intestine?

Back 104

haustrations

Front 105

T/F
The force in the Haustrations of the LI is greater and longer than that in the SI.

Back 105

True!
12-60sec

Front 106

what is the propulsive movement towards the rectum of the large intestine called?

Back 106

Mass movement

Front 107

T/F
The mass movements in the LI are longer and more frequent than the SI.

Back 107

FALSE!
the mass movements in the LI are longer, but less frequent than in the SI.

Front 108

T/F
The propulsive movements in the SI propel contents a longer distance than in the LI.

Back 108

FALSE!
The Mass movements of the LI propels contents a longer distance than in the SI.

Front 109

what affect does parasympathetic stimulation have on LI motility? sympathetic?

Back 109

increased motility; decreased motility

Front 110

where is the extrinsic voluntary control of the LI ?

Back 110

external anal sphincter

Front 111

what is the myogenic control of LI motility?

Back 111

colonic slow waves (BER)

Front 112

what are the 2 reflexes of the large intestine?

Back 112

gastrocolic and duodenocolic

Front 113

what reflex is responsible for the defecation sensation?

Back 113

duodenocolic reflex

Front 114

what prevents dribble of feces through the anus? (EWWWW)

Back 114

anal canal which is kept closed by tonic contraction of internal sphincter

Front 115

what capacity does the rectum need to be at before you sense the urge to poop?

Back 115

25%

Front 116

when the rectum is relaxed, the _____ is tonically constricted and the ____ is relaxed.

Back 116

Internal anal sphincter; external anal sphincter.

Front 117

what reflexes initiate defecation?

Back 117

rectosphincteric reflex and parasympathetic reflex

Front 118

what does the parasympathetic reflex relax?

Back 118

the internal anal sphincter

Front 119

what aspect of defecation is voluntary control?

Back 119

external anal sphincter which is controlled by the pudendal nerve

Front 120

what stimulates the urge to defecate?

Back 120

distension of the rectal sigmoid area.

Front 121

how do stretch receptors in the rectum adapt to distension stimulus?

Back 121

via rectal accommodation --> internal anal sphincter regains tonic closure

Front 122

what happens after the rectum relaxes and the internal anal sphincter regains tonic closure during the defecation reflex?

Back 122

the urge to defecate subsides, allowing the external anal sphincter to relax until another mass movement begins a new reflex cycle.

Front 123

how does an increase in intraabdominal pressure enhance propulsion of feces?

Back 123

it relaxes the pelvic floor and allows the increased abdominal pressure to force the floor downward. This will straighten the rectum and facilitate passage of feces.

Front 124

what are the two motility disorders of the LI?

Back 124

Diarrhea and constipation

Front 125

what are four possible causes of diarrhea?

Back 125

secretory, osmotic, inflammatory, and psychogenic

Front 126

what are the three possible causes of constipation?

Back 126

dietary, obstructive, irregular bowel habits

Front 127

abnormally fast stool transit is also called ___________

Back 127

diarrhea

Front 128

how long is the transit through the colon?

Back 128

30-40 hours

Front 129

what is the migrating motor complex?

Back 129

it is a cyclic pattern of electrical and motor activity during the interdigestive (fasting) state

Front 130

what initiates the migrating motor complex? inhibited?

Back 130

motilin; eating

Front 131

what is the purpose of the Migrating motor complex?

Back 131

keeps the GI clean of indigestibel meal residue, desquamated cells and prevents bacterial overgrowth.

Front 132

what is the migrating motor complex characterized by?

Back 132

vigorous and prolonged perstaltic wave at regular intervals approximately 90 minutes of 3-10min duration.

Front 133

where is this migrating motor complex initiated at? where does it move to?

Back 133

mid-body of stomach; moving distally over the caudad region and through the pylorus.

Front 134

what does the migrating motor complex cause (in regards to pyloric sphincter)?

Back 134

receptive relaxation

Front 135

what are the three phases of the migrating motor complex?

Back 135

phase 1: no contractions
phase 2: irregular contractions (~50% of slow waves are associated with spikes)
phase 3: intense contractions (100% of slow waves are associated with spikes)