GI 5: Regulation of Motility

Question 1

____cells of the ___ are the electrical pacemakers of the GI tract

Answer 1

interstitial; cajal

Question 2

interstitial cells of the cajal are modified smooth muscle cells that don’t contract, but undergo _____

Answer 2

slow wave

Question 3

do slow waves always reach threshold?

Answer 3

no

Question 4

what are slow waves?

Answer 4

undulating changes in resting membrane potential

Question 5

slow waves do not cause ______ by themselves, but set the _____

Answer 5

muscle contractions; maximal contraction frequency

Question 6

what 4 things determine if slow wave threshold is met?

Answer 6

1. stretch
2. presence of food (chemo)
3. parasympathetic stimulation
4. hormones

Question 7

can you have more thresholds than slow waves?

Answer 7

no

Question 8

with decreased ap frequency, there is less influx of __ ions and decreased tone

Answer 8

ca

Question 9

when slow waves are combined with excitatory signals , a __ is reached

Answer 9

threshold

Question 10

are ca channels slow or fast to open/close, means their ap last ___

Answer 10

slow; longer

Question 11

slow waves w/o ap can only let ___ ions in, so contraction ___happen

Answer 11

na; can’t

Question 12

what are. the 3 contractile patterns

Answer 12

1. peristalsis
2. segmentation
3. tonic contraction

Question 13

what is peristalsis and where does it occur?

Answer 13

smooth muscle activity where there is relaxation before the food blows and contraction behind it. Occurs along the entire GI tract

Question 14

peristalsis results in the ___ of the bolus

Answer 14

forward movement

Question 15

what is segmentation and where does it occur?

Answer 15

stationary contraction and relaxation of intestinal segments. occurs in the small and large intestines

Question 16

in segmentation, there is ___ net movement and results of ___ of the food bolus

Answer 16

no; mixing

Question 17

what is tonic contraction? where does it occur?

Answer 17

separation of structures and functions along the digestive tract. occurs at GI spinsters

Question 18

t/f there is very little forward movement in segmentation

Answer 18

true

Question 19

t/f peristalsis is a polarized process

Answer 19

true

Question 20

there is contraction ____cm behind the food bolus

Answer 20

2-3

Question 21

ahead of the food bolus the is ___ relaxation

Answer 21

receptive

Question 22

when excited, the myenteric plexus increases what 4 things?

Answer 22

1. tone of gut wall
2. contraction intensity
3. contraction frequency
4. velocity of contraction

Question 23

cholecystokinin (CCk) secretion is stimulated by ____ , ___ and ___and is secreted from the ____ which moderately ____ stomach contractions

Answer 23

protein, fat, and acids; I cells of the duodenum, jejunum and ileum; inhibits

Question 24

glucose-dependent insulinotropic peptide is stimulated by ___, ___ and ___ and is secreted from the ___ cells of the ___ and ___ parts of the small intestine

Answer 24

fat, amino acids, carbohydrates; K; duodenum and jejunum

Question 25

the action of the glucose dependent insulinotropic peptide moderately ____ stomach contractions

Answer 25

inhibits

Question 26

motion secretion is stimulated by cyclic release during ____. It is secreted by the ____ cells of the ___ part of the small intestine

Answer 26

fasting; M ; duodenum

Question 27

where does the voluntary stage of swallowing occur? what allows this area to act voluntarily?

Answer 27

mouth to pharnyx (made of skeletal muscle)

Question 28

what stage of swallowing is initiated by receptors in the pharynx, leading to soft palate and uvula elevation, epiglottis closing and relaxation of the esophageal spinster

Answer 28

pharyngeal (involuntary)

Question 29

what are the 3 stages of swallowing | and are they voluntary / involuntary?

Answer 29

1. voluntary (mouth to pharynx) 2. pharyngeal (involuntary) 3. esophageal (involuntary )

Question 30

the elevation of the soft palate during swallowing prevents ___

Answer 30

food getting into the nasal passageway

Question 31

what are the 3 types of motility involved in the esophageal stage of swallowing?

Answer 31

1. primary peristalsis 2. secondary peristalsis 3. tonic contractions

Question 32

t/f peristaltic waves in the esophagus go the length of the esophagus

Answer 32

true

Question 33

primary peristalsis is a continuation of peristalsis waves form the ___

Answer 33

pharynx

Question 34

what happens in primary peristalsis?

Answer 34

food pushed down the esophagus

Question 35

how long does one wave take in primary peristalsis?

Answer 35

9 sec

Question 36

what is the stimuli for primary peristalsis?

Answer 36

pharynx distention

Question 37

secondary peristalsis is initiated by ___

Answer 37

esophagus distention

Question 38

secondary peristalsis only occurs if

Answer 38

primary wasn't enough to get food to the stomach

Question 39

what are the 2 sphincters does the esophagus have?

Answer 39

upper and lower esophageal sphincters

Question 40

contraction of the upper esophageal sphincter reduces ___

Answer 40

air intake

Question 41

contraction of the lower esophageal sphincter reduces

Answer 41

acid reflux

Question 42

what is dysphagia?

Answer 42

difficulty swallowing

Question 43

dysphagia is often due to pathophysiology of the ___

Answer 43

esophagus

Question 44

dysphagia can be caused by ____, which is the loss of peristalsis in the lower esophagus and/or failure of the LES to relax and let bolus into the stomach

Answer 44

achalasia

Question 45

what is GERD?

Answer 45

increased frequency of LES opening, even w/o food bolus

Question 46

achalasia may be caused by the degeneration of neurons in the ____ plexus of the esophageal wall, especially the ___ neurons that induce relaxation of the LES

Answer 46

myenteric; inhibitory

Question 47

what are the 3 functions of the stomach?

Answer 47

1. storage of large quantity of food 2. mixing of food bolus with gastric juice 3. slow, regulated emptying of chyme into the SM Int to improve digestion and absorption

Question 48

chyme

Answer 48

food mixed with GI secretions

Question 49

receptive relaxation allows the stomach volume to reach ___L is needed

Answer 49

1.5

Question 50

receptive relaxation occurs by the ___ reflex pathway, which is stimulated by the ___ of the stomach

Answer 50

vasovagal; distention

Question 51

what are the 3 parts of the stomach?

Answer 51

fundum, body, antrum

Question 52

regulated emptying in the stomach is caused by

Answer 52

peristalsis contractions in the antrum push chyme into the duodenum, but most of it is blocked by the pyloric sphincter so it is repulsed and mixed further

Question 53

gastric emptying requires what 2 things?

Answer 53

1. increased peristalsis strength in the stomach | 2. relaxation of the pyloric sphincter

Question 54

increased peristalsis strength in the stomach occurs mainly via inhibitory signals from the duodenum : (5)

Answer 54

1. distention 2. irritation 3. chyme acidity 4. chyme osmolarity 5. protein breakdown products

Question 55

what are the 4 pathways for inhibitory signals of the duodenum to increase peristaltic strength in the stomach?

Answer 55

1. enteric NS 2. inhibitory SNS 3. vagus nerve (PNS) 4. hormones: CCK and GIP

Question 56

the max frequency of slow waves in segmentation if ___waves / per

Answer 56

12

Question 57

what are the 3 ways segmentation increases digestion and absorption??

Answer 57

1. mixing of chyme 2. minimal forward movement 3. increase contact with the walls f the small intestine

Question 58

in the fed state, peristalsis in the small intestine is ___, having short and slow contractions

Answer 58

weak

Question 59

in the fed state, it takes ___hr(s) for chyme to pass from the pylorus to the ileocecal valve

Answer 59

3-5

Question 60

motility of the small intestine id stimulated by the distention of the ___ and __ and by the hormones ___, __ and __

Answer 60

small intestine and stomach; gastrin, CCK, motilin

Question 61

motility of the small intestine is inhibited by the hormones __

Answer 61

secretin

Question 62

what type of peristalsis occurs in the fasted state in the small intestine?

Answer 62

migrating motility complex (MMC), where undigested food is moved into the large intestine

Question 63

what is the function of migrating motility complex in the fasted state>

Answer 63

transport and cleaning

Question 64

what are the 2 types of movements in the large intestine?

Answer 64

1. haustrations | 2. mass movements

Question 65

what are haustrations and their function?

Answer 65

slow (2hr) large circular and longitudinal contractions to increase absorption of water and electrolytes (e.g. Na)

Question 66

where do haustrations occur in the large intestine/

Answer 66

ascending and transverse colon

Question 67

what are mass movements and their function?

Answer 67

sustained (10-30 min) peristaltic contractions that transport ,material from the transverse colon towards to rectum

Question 68

food in the stomach (____) and food in the duodenum (____) can lead to bowel movements

Answer 68

gastrocolic reflex; duodenocolic reflex

Question 69

give an example of an irritative colon disease

Answer 69

ulcerative colitis

Question 70

what are the pouches of the large intestine called?

Answer 70

haustrums