Electrolytes and Motility

Question 1

What are the two membrane pumps of the GI system?

Answer 1

Na/K ATPase

H/K ATPase

Question 2

What are the important pores of the GI system?

Answer 2

CFTR

K channel

Question 3

What are the important exchangers (antiporters) of the GI system?

Answer 3

Na/H

Cl/HCO3

Question 4

What are the important cotransporters (symporters) of the GI system?

Answer 4

2Na/Glucose, bile salts, amino acids

Pept1 H/peptide

Question 5

What proteins are important for preventing tight junction permeability?

Answer 5

Claudin

Question 6

Where is a lot of the chloride movement on the intestine lumen?

Answer 6

Crypts

Question 7

What is an example of electroneutral absorption?

Answer 7

NaCl absorption

Question 8

What mediates fluid uptake? Electroneutral or Electrogenic absorption?

Answer 8

Electroneutral

Question 9

What is electrogenic uptake?

Answer 9

No active transport of counterion

Question 10

What is taken up in electrogenic transport? What happens to anions?

Answer 10

Na and Glucose

Anions follow in tight jinxes

Question 11

What process is vital for promoting fluid entry into intestinal lumen?

Answer 11

Chloride secretion in crypts of lieberkuhn

Question 12

What basolateral pump is vital for the chloride secretion?

Answer 12

NKCC1

Question 13

How does calcium enter the cell?

Answer 13

Transcellular or paracellular

Question 14

Where is calcium actively absorbed?

Answer 14

Duodenum

Question 15

What are important luminal transporters for iron?

Answer 15

HT (heme) and DMT1

Question 16

What effect does gastric secretion have on iron absorption?

Answer 16

Deficiency in acid?

Deficiency in iron.

Question 17

What hormones stimulate chloride secretion reflex?

Answer 17

ACh/VIP (long reflex)

5HT (short reflex)

Question 18

Agonists that elevate this promote opening of CFTR.

Answer 18

cAMP (Prostaglandins, VIP, cholera toxin)

Question 19

What effect does Guanylin have on Cl secretion?

Answer 19

Increases cGMP, increases CFTR activity

Question 20

What pathogen has the same effect as guanylin?

Answer 20

E. coli heat stable toxin

Question 21

What facilitates water absorption from stool?

Answer 21

Na+ uptake

Question 22

What effect does aldosterone have on the stool?

Answer 22

Increases ENaC expression, reclaims sodium, increases stool water absorption

Question 23

What is the root cause of secretory diarrhea?

Answer 23

Excessive secretion of chloride and NaCl transport inhibition

Question 24

Hyper motility leads to…

Hypo motility leads to…

Answer 24

Diarrhea

Constipation

Question 25

What does loperamide do?

Answer 25

Slows transit and increases sphincter tone to increase fluid absorption

Question 26

What are the four motile processes of the intestine?

Answer 26

Peristalsis to move forward Segmental contractions to mix Alterations in surface configuration Tonic contraction of sphincters

Question 27

Is the ileum or jejunum more active in mixing?

Answer 27

jejunum

Question 28

What drives the mixing contractions?

Answer 28

Basal electrical rhythm

Question 29

What factors increase small intestine motility?

Answer 29

``` ACh from vagus and enteric plexus Motilin Serotonin Substance P Prostoglandin Gastrin CCK Insulin ```

Question 30

What factors decrease intestinal motility?

Answer 30

Epinephrine Secretin Glucagon Opioid receptors

Question 31

What molecule stimulates the migrating motor complex?

Answer 31

Motilin

Question 32

What happens to the sphincter of Oddi during MMC?

Answer 32

Relaxes, leading to bile storage in intestine

Question 33

Where is the MMC active?

Answer 33

Not the large intestine!

Question 34

Why is the ileocecal sphincter tonically contracted?

Answer 34

Limits reflux into ileum (lots of bacteria in cecum)

Question 35

What causes opening of ileocecal valve?

Answer 35

Distension of ileum due to peristalsis

Question 36

What causes closure of ileocecal valve

Answer 36

Dissension of cecum (sympathetic input)

Question 37

What mediates the gastroileal reflex?

Answer 37

Gastrin and CCK

Question 38

What mediates ileal-gastric reflex?

Answer 38

Vagus nerve

Question 39

What mediates intestinointestinal reflex?

Answer 39

Extrinsic neural connections

Question 40

What mediates peristaltic reflex?

Answer 40

Increased or decreased by autonomics

Question 41

What role do taeniae coli serve?

Answer 41

Propulsion (but not super good)

Question 42

What happens between haustra?

Answer 42

Segmental contractions

Question 43

What mediates colonocolonic reflex?

Answer 43

Enteric nervous system | Modulated by sympathetic input

Question 44

What mediates gastro-colic reflex?

Answer 44

Serotonin | ACh

Question 45

What is the role of transverse folds in the rectum?

Answer 45

Retard anal leakage

Question 46

What is the pathophysiology behind Inflammatory bowel disease?

Answer 46

Release of inflammatory mediators, damaging epithelial barrier, causing NO release and diarrhea