GI 3

Question 1

What do the barriers in the GI tract function to do?

Answer 1

protect the GI tract

Question 2

Physical Barrier in the GI tract

Answer 2

mucus layer, formed by the mucins from Goblet cells in the intestinal epithelium

Question 3

Junctions b/n cells in the intestinal epithelium?

Answer 3

tight junctions

Question 4

Paneth cells

Answer 4

secrete AMP (antimicrobial peptides) into the intestinal lumen and acts as a chemical barrier

Question 5

Digestive secretions

Answer 5

gastric acid, saliva, and bile can act as a barrier in the GI tract

Question 6

Largest immunological compartment in the body?

Answer 6

GI tract

Question 7

Two Types of Immune System

Answer 7

1. Innate
2. Adaptive/Acquired

Question 8

Innate Immune Systems

Answer 8

broad specificity, first line of defense
includes macrophages, dendritic cells, and intestinal epithelial cells

Question 9

Adaptive Immune System

Answer 9

specific to antigen; have to be induced

Question 10

Intraepithelial Lymphocytes

Answer 10

adaptive immune cells present in the intestinal epithelium [and lamina propria]; lymphatics drain to the mesenteric lymph node

Question 11

Peyer’s Patches

Answer 11

aggregated follicles of lymphoid nodules; contain lymphocytes (naive B and T cells)

Question 12

M cells

Answer 12

microfold cells; uptakes antigen at epithelial surface (lumen) and presents antigen to B and T cells, which are transported to mesenteric lymph node and undergoes differentiation

Question 13

Gut-Associated Lymphoid Tissue (GALT)

Answer 13

includes intraepithelial lymphocytes, lymphocytes in the lamina propria, andlymphoid nodules (isolated or aggregated)

Question 14

What is an aggregated patch of lymphoid nodules called?

Answer 14

Peyer’s Patch

Question 15

Gut Microbiota Functions (4)

Answer 15

1. Support digestion and absoprtion
2. Maintain intestinal mucosa barrier
3. Shape the host immune system
4. Prevent colonization by pathogens

Question 16

How much more bacteria is encoded in bacteria vs. the host?

Answer 16

100 times more

Question 17

Dysbiosis

Answer 17

an imbalance (either in number or type) of microbial communities that are associated with a disease outcome

Question 18

Examples of Diseases that can cause Dysbiosis (4)

Answer 18

1. Necrotizing enterocolitis
2. IBD
3. IBS
4. GI cancer

Question 19

What are the three ways dysbiosis can have distant effects?

Answer 19

produce metabolites, stimulate cytokine secretion, or secrete pathogen associated microbial peptide into the blood

Question 20

Organs possibly affected by dysbiosis

Answer 20

heart, liver, brain, prostate, kidney, lung, islet cells

Question 21

Gut-Brain Axis

Answer 21

considered potentially relevant in diseases such as Parkinson’s and Alzheimer’s

Question 22

Intestinal Dysbiosis in Animals can affect what? (3)

Answer 22

1. Animal Health
2. Production
3. Food Safety

Question 23

6 Factors that control Microbiota Composition

Answer 23

1. Maternal Effect
2. Host Genetics
3. Diet
4. Antibiotic Use
5. Fasting (incl. travel stress)
6. Age

Question 24

How can we improve disease prevention and treatment with the gut microbiota?

Answer 24

probiotics, or prebiotics based treatment
fecal transplants

Question 25

3 Sensory Systems responsible for detecing changes in/near GI Wall

Answer 25

1. Neural sensation 2. Endocrine 3. Immune

Question 26

4 Effector Systems

Answer 26

1. Nervous System 2. Endocrine 3. Immune System 4. Non-Immune Defense System

Question 27

Motility

Answer 27

contraction and relaxation of the wall and sphincters of the gastrointestinal tract

Question 28

3 Functions of GI Motility

Answer 28

1. Break up food and mix it with secretions 2. Propel food bolus 3. Retain ingested food at specific points for digestion, absorption, or storage

Question 29

unitary smooth muscle

Answer 29

gap junctions between individual smooth muscle cells to spread the electrical signal very quickly and helps with synchronous contractions (grouped into branching bundles)

Question 30

Interstitial Cells of Cajal

Answer 30

cells closely associated with the motor neurons of the GI tract and connect to ICCs and SMCs via gap jxns

Question 31

Pacemaker of the GI Tract?

Answer 31

Interstitial Cells of Cajal

Question 32

Do interstital cells of Cajal have neurotransmitter receptors?

Answer 32

yes - can get signals from motor neurons for contraction

Question 33

Slow Wave (Basic Electric Rhythm)

Answer 33

oscillating depolarization and repolarization of the [resting] membrane electric potential in the smooth muscle

Question 34

If there are more negative ions inside the cell than outside the cell, is the membrane potential positive or negative?

Answer 34

negative

Question 35

Can basic electric rhythm generate phasic contractions?

Answer 35

No, only weak contractions - it needs contribution of action potentials from other timuli (ex: motor neurons) to reach threshold

Question 36

Origin of basic electric rhythm?

Answer 36

Interstitial Cells of Cajal (the pacemaker)

Question 37

What controls the contractile parameters of frequency, propagation velocity and direction?

Answer 37

slow wave (basic electric rhythm)

Question 38

Basic Electric Rhythm

Answer 38

Slow Wave

Question 39

Slow Wave

Answer 39

Basic Electric Rhythm

Question 40

Do slow waves require neural or hormonal input to occur?

Answer 40

No, they're independent

Question 41

Effect of Excitatory Molecules on Slow Wave

Answer 41

elevates baseline membrane potential and increases the chance of an action potential

Question 42

Are slow waves consistent throughout the entire GI tract?

Answer 42

no

Question 43

What part of the GI tract has the lowest BER frequency?

Answer 43

stomach

Question 44

2 Types of Contractions

Answer 44

1. Tonic (sustained) 2. Phasic (rhythmic)

Question 45

What type of contraction can occur without an action potential?

Answer 45

tonic contraction

Question 46

Tonic contraction

Answer 46

maintain constant level of weak contraction w/o regular periods of relaxation (minutes to hours)

Question 47

Examples of Tonic Contractions in the GI (5)

Answer 47

lower esophageal sphincter, pylorus, fundus/body of stomach, ileocecal sphincter, internal anal sphincter

Question 48

Phasic Contractions

Answer 48

periodic contractions followed by relaxation (seconds)

Question 49

Can phasic contractions occur without an action potential?

Answer 49

no

Question 50

Examples of Phasic Contractions in the GI (3)

Answer 50

esophageal body, distal stomach, intestines

Question 51

myogenic

Answer 51

smooth muscle contractions independent of neural input or membrane voltage