1. GI Pharm

Question 1

The GI mediates ___ and ___ of nutrients and oral drugs

Answer 1

Absorption and digestion

Question 2

What are the 4 chemical messengers of the GI endocrine system?

Answer 2

5-HT, gastrin, ghrelin, and CCK

Question 3

What are the 5 organs of digestion?

Answer 3

Tongue, salivary glands, pancreas, gallbladder, liver

Question 4

What are the 4 components of the digestive tract?

Answer 4

Mouth, esophagus, stomach, intestines

Question 5

What are the 8 layers of the intestine wall (going out from the lumen)?

Answer 5

-Mucosa-
1. Epithelium
2. Lamina propria
3. Muscularis mucosae

4. Submucosa

-Muscularis-
5. Circular muscle
6. Longitudinal muscle

Serosa:
7. Areolar connective tissue
8. Epithelium

Question 6

What is the serosa?

Answer 6

Thin epithelium + underlying areolar connective (loose) tissue lining the GIT

Question 7

What is the muscularis?

Answer 7

A thin layer of longitudinal and circular muscle separating the serosa and submucosa

Question 8

What is the submucosa?

Answer 8

Thin tissue connecting the mucosa and the muscularis

Question 9

What is the mucosa?

Answer 9

The epithelial lining of the GI cavity with the lamina propria and muscularis mucosae

Question 10

What is the lamina propria?

Answer 10

Thin connective tissue nourishing the epithelium of the mucosa

Question 11

What is the muscularis mucosae?

Answer 11

Thin muscle layer outside the lamina propria of the muscoa, separating it from the submucosa

Question 12

Submucosal plexus/_____?

Answer 12

Meissner’s plexus

Question 13

Myenteric plexus/____?

Answer 13

Auerbach’s plexus

Question 14

What is the enteric nervous system (ENS)?

Answer 14

The intrinsic signalling within the GIT controlling motility, secretion, BF, and immunity

Question 15

The ENS is sometimes regulated by the?

Answer 15

ANS

Question 16

What is the submucosal plexus?

Answer 16

The intrinsic signalling system within the epithelia and muscle cells of the GIT

Question 17

What is the myenteric plexus?

Answer 17

The intrinsic signalling system between the muscularis layers, regulating them for motility and secretion

Question 18

The PNS interacts with the ENS via…

Answer 18

Acetylcholine (vagal fibres)

Question 19

The SNS interacts with the ENS via…

Answer 19

Noradrenaline

Question 20

What action do vagal fibres have in the GIT?

Answer 20

Mainly excitatory, increasing gut function
- ^ motility and secretion
- ^ transit by dilating sphincters

Question 21

What action does the ENS have on the CNS?

Answer 21

Signalling
- spinal and brainstem reflexes for digestion
- ANS for fed and ill states
- noxious and non-noxious sensation

Question 22

What is peristalsis?

Answer 22

Movement of food from mouth –> anus (aboral) via muscle contraction and relaxation

Question 23

What is segmentation?

Answer 23

Mixing of food to facilitate digestion

Question 24

Contraction of sphincters is (type)

Answer 24

Tonic (continuous without relaxing), keeps the sphincters closed

Question 25

Contraction of the small intestine and colon is (type)

Answer 25

Phasic (periodic relaxing and contracting), during peristalsis

Question 26

Which type of contraction is driven by slow waves?

Answer 26

Phasic

Question 27

Slow waves originate from...

Answer 27

The myenteric plexus

Question 28

What are slow waves?

Answer 28

The resting electrical rhythm of the GIT that causes spiking activity (APs) once threshold is reached and controls its propogation

Question 29

Describe the steps that occur after a slow wave reaches threshold

Answer 29

Voltage-gated Ca2+ channel opens --> Ca2+ enters --> depolarization/AP firing --> muscle contraction

Question 30

Isolated contractions move stomach contents...

Answer 30

Orally and aborally (both)

Question 31

Which muscles are involved in gut motility?

Answer 31

Circular and longitudinal muscles in the muscularis mucosae

Question 32

What triggers the peristaltic reflex?

Answer 32

Mechanical stretch and mucosal stimulation

Question 33

What is the peristaltic reflex?

Answer 33

Stretch of GIT --> release of 5-HT from ECCs --> ENS neurons release ACh --> activate +motoneurons above bolus and -motoneurons below bolus, causing peristalsis

Question 34

What is gastrin?

Answer 34

Mucosal (EEC - G cells) hormone that stimulates CCK2 receptors (ECL cells) to secrete histamine (ECCs) for stimulating parietal cells

Question 35

What is motilin?

Answer 35

Mucosal (EEC) hormone that stimulates GI muscle contraction

Question 36

What is cholecystokinin (CCK)?

Answer 36

Small intestine (EEC) hormone that stimulates pancreatic enzyme secretion

Question 37

Which gut hormone comes from ECCs?

Answer 37

5-HT

Question 38

What is GLP-1?

Answer 38

Peptide hormone that stimulates insulin release, inhibits glucagon release (glucagon-like), and causes satiety

Question 39

____ cells secrete proenzymes

Answer 39

Peptic chief cells

Question 40

What is pepsin?

Answer 40

Endopeptidase, breaks down proteins in stomach after conversion from pepsinogen

Question 41

What is rennin?

Answer 41

Endopeptidase, breaks down proteins in stomach after conversion from prorennin

Question 42

___ cells secrete HCl

Answer 42

Parietal cells

Question 43

How much gastric juice is secreted by the stomach in one day?

Answer 43

~2.5L

Question 44

What is the pH of HCl?

Answer 44

1-2

Question 45

Why is HCl the stomach acid of choice?

Answer 45

High pH = proteolysis for proenzyme conversion, killing pathogens, and iron absorption

Question 46

How does HCl promote iron absorption?

Answer 46

Fe2+ > Fe3+ in low pH, which is better absorbed than Fe3+

Question 47

Which cells secrete PGs?

Answer 47

Mucosal (EECs) cells

Question 48

What are the 3 mechanisms of action of PGs in the stomach?

Answer 48

1. Mucosal cell stimulation 2. Histamine inhibition (ECL cells) 3. Vasodilation

Question 49

What are the mucosal PG receptors involved in stomach protection?

Answer 49

EP1, 2, and 4

Question 50

What are the ECL cell-acting PG receptors involved in stomach protection?

Answer 50

EP2/3

Question 51

What are the vascular PG receptors involved in stomach protection?

Answer 51

EP2/4

Question 52

EP4 stimulation causes ____ to protect the stomach

Answer 52

Mucus secretion and vasodilation

Question 53

EP2 stimulation causes ____ to protect the stomach

Answer 53

HCO3- secretion, inhibition of His, and vasodilation

Question 54

EP1 stimulation causes ____ to protect the stomach

Answer 54

HCO3- secretion

Question 55

EP3 stimulation causes ____ to protect the stomach

Answer 55

Inhibition of histamine release

Question 56

How does vasodilation aid stomach protection?

Answer 56

Increased blood flow to muscosa = protection and healing

Question 57

What is the result of the combined EP activation on the mucosa?

Answer 57

Forms a gel surface pH = 6-7 on the mucosa

Question 58

What do parietal cells secrete?

Answer 58

H+, Cl-, K+

Question 59

How is K+ secreted from parietal cells?

Answer 59

Cl-/K+ cotransporter

Question 60

What is the difference in pH between the parietal cell and the stomach?

Answer 60

pH = 7.2 vs pH = 1-2 10^5 fold gradient being pumped against

Question 61

Where does H+ come from in a parietal cell?

Answer 61

Carbonic anhydrase: H2O + CO2 --> HCO3- + H+

Question 62

Where does Cl- come from in a parietal cell?

Answer 62

HCO3-/Cl- antiporter brings Cl- in and HCO3- out into the plasma

Question 63

Where does histamine come from?

Answer 63

ECL cells

Question 64

H2 receptors are (type) receptors

Answer 64

GsPCR

Question 65

How does histamine enable acid secretion into the stomach?

Answer 65

ECL cells produce histamine --> H2 receptors on parietal cells --> Gs signalling cascade = cAMP --> H+/K+ pump

Question 66

Where are H2 receptors located?

Answer 66

Parietal cells

Question 67

How are G cells stimulated?

Answer 67

Nerve stimulation and stomach contents (a.a's, Ca2+)

Question 68

What are the ways parietal cells are stimulated?

Answer 68

1.