GIT - Lecture 6

Question 1

How is the GI motility organized in the interdigestive period?

Answer 1

into an intense pattern of cyclic myoelectric (motor) activity

Question 2

How often does the intense pattern of cyclic myoelectric activity recur in the GIT in the absence of a meal?

Answer 2

every 90 minutes

Question 3

Where does the cyclic motor activity of the GIT move during the interdigestive period?

Answer 3

over the distal stomach and small intestine

Question 4

What is the rate of GI motility during the interdigestive period?

Answer 4

moves over portions of the GIT at 2-10 cm/minute

Question 5

How many phases are in the migrating myoelectric complex?

Answer 5

3

Question 6

What happens to spike potentials and contractions during phase I of the MMC?

Answer 6

no spike potentials, no contractions

Question 7

What happens to spike potentials and contractions during phase II of the MMC?

Answer 7

irregular spike potentials and contractions

Question 8

What happens to spike potentials and contractions during phase III of the MMC?

Answer 8

regular spike potentials and contractions

Question 9

Why is it called the “migrating” myoelectric complex

Answer 9

because it moves down the length of the GIT

Question 10

How long does phase I of the MMC last?

Answer 10

60 min

Question 11

How long does phase II of the MMC last?

Answer 11

20 min

Question 12

How long does phase III of the MMC last?

Answer 12

10 min

Question 13

When is the MMC interrupted?

Answer 13

when we consume a meal

Question 14

Why is the MMC important?

Answer 14

because it allows us to move food in the interdigestional period that haven’t moved at other times

Question 15

What is the function of the MMC?

Answer 15

gastric emptying of large, nondigestible particles even in the absence of a meal

Question 16

Which nervous system does the MMC need in order to be initiated?

Answer 16

the enteric nervous system

Question 17

Which nervous system does the MMC need in order to be propagated?

Answer 17

the enteric nervous system

Question 18

What helps the ENS propagate MMC?

Answer 18

ANS and gut peptides

Question 19

What is the function of the exocrine secretions?

Answer 19

chemical breakdown of food

Question 20

What are the 2 kinds of gland secretion?

Answer 20

endocrine and exocrine

Question 21

Are gland secretions that move into GIT external environment considered exocrine or endocrine?

Answer 21

exocrine

Question 22

Are gland secretions that move into the blood stream and internal environment considered exocrine or endocrine?

Answer 22

endocrine

Question 23

What is important to consider about the enzymes involved in digestion?

Answer 23

their medium requirements: pH, ions

Question 24

Digestion results from the secretory activity of a large number of ___ glands found within and in association with the GIT.

Answer 24

exocrine

Question 25

Where are exocrine secretions released in the digestive tract?

Answer 25

the lumen

Question 26

What kind of process is secretion?

Answer 26

active, energy and blood flow dependent

Question 27

What does secretion result in the release of?

Answer 27

fluids containing ions and enzymes

Question 28

What are the 3 types of digestive enzymes?

Answer 28

- amylases - proteases - lipases

Question 29

What is the pattern of nervous system regulation of secretion?

Answer 29

decreases from proximal -> distal

Question 30

What is the pattern of hormonal regulation of secretion?

Answer 30

increases from proximal -> distal

Question 31

Which nervous system regulates secretion?

Answer 31

ANS

Question 32

Which hormones regulate secretion?

Answer 32

gut peptides

Question 33

What are the 3 salivary glands?

Answer 33

- parotid - submandibular - sublingual

Question 34

Which secretion of the mouth protects and lubricates?

Answer 34

mucin

Question 35

What does mucin lubricate?

Answer 35

the bolus

Question 36

Which 2 secretions in the mouth allow for chemical digestion?

Answer 36

- salivary amylase - lingual lipase

Question 37

What does salivary amylase begin?

Answer 37

carbohydrate digestion

Question 38

What does lingual lipase begin?

Answer 38

lipid digestion

Question 39

What fluid does the parotid gland release?

Answer 39

serous fluid

Question 40

What fluid does the sublingual gland release?

Answer 40

mucin-rich fluid

Question 41

What fluid does the submandibular gland release?

Answer 41

mixed fluid (serous + mucin-rich)

Question 42

Which is the only secretion in the GIT that is hypotonic?

Answer 42

saliva

Question 43

What is the volume of saliva produced every day?

Answer 43

0.5-1.5 liters/day

Question 44

What are the 4 ions present in saliva?

Answer 44

Na+, K+, Cl-, HCO3-

Question 45

What is the pH of saliva? Why?

Answer 45

6.5-7.0 because of the bicarbonate secreted into it

Question 46

What can starch (polysaccharide) be broken down into by saliva? With which enzyme?

Answer 46

maltose by the enzyme ptylin

Question 47

Where does lipase break down fats?

Answer 47

at the level of the stomach

Question 48

What do lysozymes break down?

Answer 48

bacterial cell walls

Question 49

What do lysozymes protect us from?

Answer 49

bacteria in food

Question 50

Which branch of the ANS increases secretion?

Answer 50

parasympathetic system

Question 51

How can you block secretion?

Answer 51

by giving atropine

Question 52

What happens when ACh is released onto a secretory cell?

Answer 52

it will depolarize and the depolarization will lead to secretion (exocytosis)

Question 53

What also increases when secretion increases?

Answer 53

vasodilation

Question 54

What would happen to secretion if the sympathetic system were activated?

Answer 54

it would decrease

Question 55

Does the sympathetic system cause vasoconstriction or vasodilation?

Answer 55

vasoconstrction

Question 56

What activates afferents that feed into the salivary centres in the medulla?

Answer 56

sensory receptors in the mouth

Question 57

What do the salivary centres in the medulla send out to the salivary glands?

Answer 57

efferents via parasympathetic supply

Question 58

What activates higher centres in the cortex and then in turn activates salivary centres in medulla?

Answer 58

smelling food or seeing food

Question 59

What is the first phase of secretion?

Answer 59

cephalic

Question 60

What is the cephalic phase made of?

Answer 60

- psychic - gustatory

Question 61

What are the 3 phases of secretion?

Answer 61

1. cephalic 2. gastric 3. intestinal

Question 62

How much mixed gastric juice is produced per day?

Answer 62

1.5-2 L/day

Question 63

What are the ions found in mixed gastric juice?

Answer 63

Na+, K+, Cl-, H+

Question 64

Which ion is the most important in mixed gastric juice?

Answer 64

H+

Question 65

What is the pH of mixed gastric juice?

Answer 65

1-2

Question 66

What kind of fluid is mixed gastric juice?

Answer 66

isotonic

Question 67

What gives the stomach its low pH?

Answer 67

the HCl found within it

Question 68

What are the 4 main components of mixed gastric juice?

Answer 68

- HCl - pepsinogen - intrinsic factor - mucin

Question 69

Which enzymes break down proteins into smaller proteins? (4)

Answer 69

- pepsin - trypsin - chymotrypsin - elastase

Question 70

Which enzymes break down smaller peptides into individual amino acids? (2)

Answer 70

- aminopeptidase - carboxypeptidase

Question 71

What do surface epithelial cells throughout the GIT secrete? (2)

Answer 71

mucous and alkaline fluid

Question 72

How do we increase the surface area of secretion in the stomach?

Answer 72

by tubular glands

Question 73

What kind of fluid do the cardiac and pyloric tubular glands secrete?

Answer 73

alkaline, mucin-rich fluid

Question 74

What kind of fluid do the fundus and body tubular glands secrete? (3)

Answer 74

acid, enzymes and intrinsic factor

Question 75

What are the 3 important cells found in the fundus and body of the stomach?

Answer 75

parietal cells, chief cells, mucus neck cells

Question 76

What do parietal cells release into the lumen of the tubular gland?

Answer 76

HCl

Question 77

What do chief cells release?

Answer 77

pepsinogen

Question 78

What do mucus neck cells produce?

Answer 78

mucus and alkaline fluids

Question 79

What do surface epithelial cells release?

Answer 79

HCO3 and mucus

Question 80

What do the canaliculi of the parietal cells do?

Answer 80

increase their apical surface area for the secretion of HCl

Question 81

What do parietal cells have a lot of? Why?

Answer 81

mitochondria, because producing HCl requires a lot of energy

Question 82

What is the mEq of H+ and Cl- of the HCl produced by the parietal cells?

Answer 82

150 mEq H+ and 150 mEq Cl-

Question 83

For every HCl molecule moving into the lumen, 1 molecule of ___ is going to move into the capillary.

Answer 83

HCO3- (bicarbonate)

Question 84

As we acidify the lumen, we create an ___ of the blood.

Answer 84

alkalization

Question 85

Cl- entering the cell is ___ transported across the canalicular membrane.

Answer 85

actively

Question 86

H+ available from the dissociation of intracellular water, is also actively pumped into the canaliculi in exchange for ___.

Answer 86

K+

Question 87

What does the secretion of H+ leave an excess of in the cell?

Answer 87

OH-

Question 88

What happens to pH when there is an excess of OH- in the cell?

Answer 88

it increases

Question 89

When there is an increase in the intracellular pH, what happens to CO2?

Answer 89

it diffuses in from the plasma and combines with water to produce H2CO3

Question 90

When does CO2 combine with water in the presence of?

Answer 90

carbonic anhydrase

Question 91

What does H2CO3 react with to produce H20 and HCO3?

Answer 91

excess OH-

Question 92

What happens to the alkalinity in the venous blood during HCl secretion?

Answer 92

it increases