GIT - Lecture 5

Question 1

What is vomiting?

Answer 1

the emptying of the contents of the upper GIT

Question 2

What does vomiting result from?

Answer 2

an increase in intraabdominal pressure

Question 3

What increases intraabdominal pressure during vomiting?

Answer 3

the action of the diaphragm and the abdominal muscles

Question 4

Is the GIT passive or active during vomiting?

Answer 4

passive

Question 5

What happens to the proximal stomach and above before vomiting?

Answer 5

they relax

Question 6

What happens to the upper duodenum and distal stomach before vomiting?

Answer 6

they contract

Question 7

What happens to the diaphragm and the abdominal muscles during vomiting?

Answer 7

diaphragm: lowers
abdominal muscles: contract

Question 8

During vomiting, the intraabdominal pressure overcomes ___.

Answer 8

LES

Question 9

What is the vomiting centre near?

Answer 9

fourth ventricle

Question 10

What activates the vomiting centre?

Answer 10

afferents

Question 11

What can send afferents to the vomiting centre? (6)

Answer 11

 Pharyngeal Stimulation
 GIT or urogenital distension
 Pain, cardiac ischemia
 Biochemical disequilibrium
 Vestibular Signals
 Psychogenic Factors

Question 12

What does the vomiting centre activate once it has activated?

Answer 12

efferents

Question 13

What are the 4 efferent outputs of the vomiting centre?

Answer 13

1. widespread autonomic discharge
2. nausea
3. retching
4. emesis

Question 14

Why do you feel cold/sweaty when you want to vomit?

Answer 14

because the efferents are involved in both the sympathetic and the parasympathetic system which are imbalanced

Question 15

What do the efferents lead to in the parasympathetic and the sympathetic activities?

Answer 15

an imbalance

Question 16

What actions precede and accompany vomiting?

Answer 16

sweating, vasoconstriction, salivation, alternating bradycardia, tachycardia

Question 17

What does emesis do to the upper GI tract + pyloric antrum and duodenum?

Answer 17

upper GI tract: relaxation
pyloric antrum and duodenum: spasm

Question 18

What does emesis do to the abdominal muscles and diaphragm?

Answer 18

contraction

Question 19

What is the second region in the brain that can lead to vomiting?

Answer 19

chemoreceptor trigger zone

Question 20

Is the chemoreceptor trigger zone inside or outside the blood-brain barrier?

Answer 20

outside

Question 21

What can act on the chemoreceptor trigger zone within the medulla?

Answer 21

circulating emetic agents

Question 22

Where does the CTZ send signals to?

Answer 22

the vomiting centre

Question 23

Why is it important that the CTZ is outside the blood-brain barrier?

Answer 23

so that it can be activated by the circulating emetic agents

Question 24

What are the 3 stages of vomiting?

Answer 24

1. nausea
2. retching
3. emesis

Question 25

What is nausea?

Answer 25

a psychic experience

Question 26

What is retching?

Answer 26

abrupt, uncoordinated respiratory movements with glottis closed

Question 27

What is emesis?

Answer 27

actual expulsion of contents of upper GIT

Question 28

What is the process of vomiting?

Answer 28

the individual takes a deep breath, glottis closes, abdominal muscles contract, exerting pressure on gastric contents

Question 29

What happens to the thoracic pressure and diaphragm once emesis is completed?

Answer 29

thoracic pressures: negative -> positive diaphragm: displaced upwards

Question 30

Where does most digestion and all absorption of nutrients occur?

Answer 30

the small intestine

Question 31

What are the 3 regions of the small intestine?

Answer 31

- duodenum - jejunum - ileum

Question 32

What are the 4 functions of the upper small intestine (mostly duodenum)?

Answer 32

1. neutralization 2. osmotic equilibration 3. digestion 4. absorption

Question 33

Why does chyme entering the stomach need to be rapidly neutralized?

Answer 33

because it is highly acidic

Question 34

Which mucosa is well protected from acid? Which one isn't?

Answer 34

stomach mucosa is, small intestine isn't

Question 35

When will chyme be isotonic?

Answer 35

by the time it leaves the duodenum

Question 36

What are the 2 motor activities of the small intestine?

Answer 36

- effective mixing - slow propulsion

Question 37

How long can an eaten meal be in the small intestine for?

Answer 37

2-6 hours

Question 38

What are the intestinal contractions governed by?

Answer 38

electrical characteristics of smooth muscle

Question 39

What is frequency of the small intestine governed by?

Answer 39

BER (ECA)

Question 40

What are the spikes of the small intestine initiated by?

Answer 40

stretch or ACh

Question 41

What is the amplitude of contraction of the small intestine related to?

Answer 41

the number of spikes/burst of ERA

Question 42

What does intrinsic frequency of BER vary in the small intestine?

Answer 42

different cells of the small intestine

Question 43

What happens to the frequency of BER from proximal to distal intestine?

Answer 43

it declines

Question 44

What is present along the entire length of the SI?

Answer 44

pacemaker cells

Question 45

What is the frequency of BER in the duodenum compared to the ileum?

Answer 45

duodenum: 12 cycles/min ileum: 8 cycles/min

Question 46

What do the contractions of the small intestine contribute to?

Answer 46

the foreward movement of contents

Question 47

Both the frequency and the amplitude of muscle contractions are ___ in the proximal small intestine.

Answer 47

greater

Question 48

Does the maximal contractile activity in the small intestine exceed the BER frequency of that gut segment?

Answer 48

no, it cannot

Question 49

What is the most common type of contractile activity in the SI after a meal?

Answer 49

segmentation

Question 50

What initiates segmentation in the SI?

Answer 50

myogenic response to distention

Question 51

What coordinates and organizes contraction over a length of small intestine in the GI?

Answer 51

ENS

Question 52

What can modulate what happens at the musculature of the SI?

Answer 52

ANS and hormones

Question 53

What happens to parasympathetic and sympathetic in the SI after a meal?

Answer 53

parasympathetic: increases sympathetic: decreases

Question 54

What is the function of segmentation?

Answer 54

mixing and slow propulsion

Question 55

How does mixing cause slow propulsion?

Answer 55

since there are more contractions and stronger contractions proximally, there will be a slow, net aboral propulsion of contents

Question 56

Proximal: ___ contractions

Answer 56

more + stronger

Question 57

Distal: ___ contractions

Answer 57

fewer + weaker

Question 58

How is peristalsis in the small intestine characterized?

Answer 58

- infrequent, irregular - weak, shallow - travels for short distances

Question 59

What is intestinal peristalsis mediated by?

Answer 59

a series of local reflexes

Question 60

Intestinal peristalsis involves interactions of which 2 muscles?

Answer 60

longitudinal and circular

Question 61

Maximum frequency ___ exceed frequency of BER.

Answer 61

cannot

Question 62

What is intestinal peristalsis modulated by (2)?

Answer 62

ANS and hormones

Question 63

What is the pathway of the "Law of the Intestine"?

Answer 63

radial stretch -> receptors -> neurally mediated

Question 64

When does contraction of longitudinal muscle and relaxation of circular muscle occur?

Answer 64

ahead of the bolus

Question 65

What is found between the ileum and the colon?

Answer 65

ileocecal sphincter

Question 66

What is the first portion of the colon called?

Answer 66

cecum

Question 67

Is the ileocecal sphincter open or closed normally?

Answer 67

closed

Question 68

What is the colon contractile activity similar to?

Answer 68

SI but slower and more sluggish/irregular

Question 69

What does the colon absorb?

Answer 69

water and some ions

Question 70

How much water enters the ileocecal sphincter per day?

Answer 70

1500 mL

Question 71

How much water is expelled from the colon each day?

Answer 71

200 mL

Question 72

What are the functions of the colon?

Answer 72

1. mixing 2. propulsion 3. storage

Question 73

What is the rate of colon propulsion?

Answer 73

slow

Question 74

How long does the colon take to convert chyme to feces?

Answer 74

50-60 hours

Question 75

What is governed by irregular BER in the colon?

Answer 75

segmentation and peristalsis

Question 76

How and when does the large intestine empty its contents?

Answer 76

2-3x a day, corresponding to the intake of a new meal

Question 77

Why does the large intestine empty its contents?

Answer 77

because there is increased activity in the colon and distal SI

Question 78

What are the 3 reflexes produces after the intake of a meal?

Answer 78

- gastroileal reflex - gastrocolic reflex - ileocolic reflex