2.09 Reflexes, Fluid, and Electrolyte Balance

Question 1

What is the basal state of stomach secretion?

Answer 1

low H+ secretion
circadian rhythm
lower between meals

Question 2

What are the 3 phases of acid secretion?

Answer 2

cephalic
gastric
intestinal

Question 3

Phase where 30% HCl secreted into gastric lumen prior to entry of food into stomach sensed by chemo/mechanoreceptors (stimuli) mediated by vagus nerve?

Answer 3

cephalic phase

Question 4

What are the mechanisms at play for the cephalic phase?

Answer 4

vagus nerve
parietal cells
ECL cells
GRP - G cells
(inhibition) D cells-somatostatin

Question 5

Phase where 60% Hcl secreted with food now in the stomach stimulated by distension and partially digested proteins (G cells)?

Answer 5

gastric phase

Question 6

Gastric phase mechanism?

Answer 6

Local ENS reflex - ACh

Vagoavagal reflex
(Antral G cell + ECL)
ACh + GRP + Gastrin

Gastrin-Histamine Stim

Question 7

What receptor does ACh attach to on the Antral G cell, ECL cell, and parietal cell respectively?

Answer 7

M3

Question 8

Phase where 10% HCl secreted when food leaving the stomach and entering the intestine, the small intestine can signal the stomach to make more acid since it doesn’t have parietal cells?

Answer 8

Intestinal Phase

Question 9

Mechanism for intestinal phase?

Answer 9

protein digestion products trigger
(G cell + endocrine cell + absorbed AA)
gastrin & “entero-oxyntin” to parietal cells

Nervous & Humoral

Question 10

hormone
released by the duodenum in response
to acidic chyme entering from the
stomach

Answer 10

Secretin (from S cells)

Question 11

Secretin will work to trigger what from the pancreas to help
neutralize the acid in the upper
duodenum?

Answer 11

bicarbonate
(HCO3-)

Question 12

What generally excites pepsin and acid production?

Answer 12

parasympathetics

Question 13

What CCK? What does it do?

Answer 13

From I cells @duodenum they allow pancreas,
gallbladder, stomach
Increase enzyme secretion, contracts
gallbladder, decreases gastric emptying

Question 14

What is absorbed at the small intestine?

Answer 14

Water, Sodium, Chlorine, Potassium

Question 15

What is secreted at the small intestine?

Answer 15

HCO3

Question 16

How much of the 8.5L/day fluid load that reaches the small intestine is reabsorbed?

Answer 16

6.5L/day

Question 17

What makes up the body fluid load that the small and large intestine work at reabsorbing?

Answer 17

food, saliva, secretions (gastric, pancreatic, bile, small intestine)

Question 18

How much of the 2L/day fluid that reaches the colon reabsorbed? How much is excreted in feces?

Answer 18

1.9L/day reabsorbed

0.1L/day excreted

Question 19

What is the max absorptive capacity of the colon?

Answer 19

4-6L/day

Question 20

What is absorbed at the distal colon?

Answer 20

Water, Na, Cl

Question 21

What is secreted at the distal colon?

Answer 21

K+ and HCO3

Question 22

What happens if there is excess fluid at the colon?

Answer 22

diarrhea

Question 23

What is required to maintain the Na+ driving force across the apical membrane?

Answer 23

Na+/K+ pump

Question 24

What kind of absorption is dominant in the small intestine?

Answer 24

Na+ nutrient coupled (ex. glucose + AA)

Question 25

An increased prevalence of what in the intestinal lumen can help enhance Na+ absorption?

Answer 25

glucose or amino acids

Question 26

How does glucose stimulate more Na+ reabsorption at small intestine?

Answer 26

osmotic gradients (cAMP independent)

Question 27

What can you recommend that a mild dehydrated and acidotic patient with diarrhea take to replenish absorption?

Answer 27

oral rehydration solution (ORS) (Glucose + electrolytes)

Question 28

How does the small intestine and colon absorb Na+?

Answer 28

apical and basolateral membrane transport processes (passive and active)

Question 29

How does the small intestine and colon absorb Cl-?

Answer 29

apical and basolateral membrane transport processes or paracellular/transcellular* (passive)

Question 30

What are the ways that Cl- can be reabsorbed?

Answer 30

passive trans/paracell Cl-HCO3 exchange Na-H parallel

Question 31

Where does the electrogenic Cl- secretion occur?

Answer 31

crypts of small and large intestine

Question 32

What are the Cl- secretion mechanisms?

Answer 32

Na-K pump Na/K/Cl cotransporter 2 types of K+ channels

Question 33

What is the Cl- channel present at the apical membrane?

Answer 33

cystic fibrosis transmembrane conductance regulator [CFTR]

Question 34

The net result of Cl- secretion is responsible for what?

Answer 34

secretion of NaCl

Question 35

What parts of the GI are responsible for the dynamic K+ reabsorb/secrete balance?

Answer 35

small intestine absorbing K+ distal intestine secreting K+

Question 36

How does K+ absorption in small intestine likely occurs?

Answer 36

solvent drag

Question 37

How does passive K + secretion in colon occurs?

Answer 37

lumen-negative Vm via tight junctions

Question 38

How is active K + secretion mediated?

Answer 38

aldosterone and cAMP

Question 39

Where does active K+ secretion take place and what fuels it?

Answer 39

distal colon fueled by apical H-K pump

Question 40

What are common Vitamin K food sources?

Answer 40

brussels sprouts, pork chops, avocadoes, broccoli, kale, spinach, liver, chicken, kiwi, prune, green beans and peas