18 Intestinal Fluid and Electrolyte Secretion and Absorption

Question 1

These are semi-long cards, but it’s sheer memorization, and I spent a lot of time condensing/organizing the info for you :)

Answer 1

Each card will list gut location, then the key characteristics of each absorption method.

Question 2

What are the 4 sodium absorption methods?

Answer 2

• Na/Glu symport (electrogenic)
• Na/H antiport
• Na/H with Cl/HCO3 antiport (electroneutral)
• Na electrogenic absorption

Question 3

2 Characteristics of Na/H antiport?

Answer 3

• jejunum more than duodenum

- Stimulated by alkaline lumen (due to pancreatic HCO3 w/ meals)

Question 4

4 Characteristics of Na/H, CL/HCO3 antiport (electroneutral)?

Answer 4

• ileum & proximal colon
• Primary Na absorption mech. between meals
• Regulated by intracellular pH
• Down due to cAMP, cGMP, Ca++

Question 5

4 Characteristics of electrogenic Na absorption?

Answer 5

• Distal colon
• ENaC
• Up due to aldonsterone, mineralocorticoids
• Driven by Na/K ATPase

Question 6

3 Characteristics of Na/Glu symport?

Answer 6

• jejunum more than ileum
• Driven by Na/K ATPase
• Primary mech. for Na absorption when glucose present.

Question 7

What are the 4 Cl absorption/secretion methods?

Answer 7

• Cl passive (voltage dependent)
• CL/HCO3 electroneutral
• Na/H, CL/HCO3 electroneutral
• Cl secretion

Question 8

1 Characteristic of Cl/HCO3 (electroneutral) absorption?

Answer 8

-ileum and colon

Question 9

3 Characteristics of Cl passive (voltage-dependent) absorption?

Answer 9

• jejunum most, ileum & distal colon
• Follows Na (linked to electrogenic Na absorption)
• Can be para or transcellular

Question 10

What’s special about Na/H, Cl/HCO3 electroneutral Cl absorption?

Answer 10

It’s the same as Electroneutral Na/H, Cl/HCO3 absorption!

Question 11

4 Characteristics of Cl secretion?

Answer 11

• jejunum, ileum, colon
• Normally lower than absorption, but when massive->diarrhea
• Occurs in crypts
• Secretagogues stimulate this

Question 12

What are the 4 K absorption/secretion methods?

Answer 12

• Paracellular solvent drag absorption
• Absorption by K/H ATPase
• Passive (electrogenic) secretion paracellularly
• Active K secretion

Question 13

1 characteristic of paracellular K absorption?

Answer 13

duodenum, jejunum, ileum

Question 14

3 characteristics of K/H ATPase K absorption?

Answer 14

• Distal colon
• Only occurs in K depleted state
• Dif than gastric H/K antiporter

Question 15

3 Characteristics of passive K secretion (paracellular)?

Answer 15

• Distal colon
• Compensates for Na electrogenic absorption
• Primary mech. of colon K secretion

Question 16

3 Characteristics of Active K secretion?

Answer 16

• colon
• Boosted by Na/K ATPase
• Induced by cAMP & aldosterone

Question 17

What is the major secretagogue that drives Cl secretion?

Answer 17

ACh (acts on ENS)

Question 18

Lamina propria immune cells make 3 secretagogues. What are they?

Answer 18

histamine (mast cells), prostaglandins (macrophages), eicosanoids (neutrophils, fibroblasts)

Question 19

Exotoxin secretagogues are made by what 2 bacteria we should know?

Answer 19

E. coli, cholera

Question 20

Laxatives are what?

Answer 20

secretagogues

Question 21

What effect on ion transport do ALL secretagogues have?

Answer 21

inhibit NaCl absorption, increase Cl secretion

Question 22

What are the 3 products that are upregulated as a mechanism

of secretagogue action?

Answer 22

-Up cAMP, Ca++, cGMP

Question 23

What are the 3 absorptagogues?

Answer 23

mineralocorticoids, glucocorticoids, somatostatin

Question 24

How do mineralocorticoids work on intestines?

Answer 24

Up Na absorption, K secretion in colon only

Question 25

How do glucocorticoids work on intestines?

Answer 25

up electroneutral Na uptake in small, large intestine

Question 26

How does somatostatin work on intestines?

Answer 26

up electroneutral NaCl absorption, down electrogenic HCO3 secretion

Question 27

For severe dehydration, what treatment should be given?

Answer 27

isotonic saline, or fluids w/ electrolytes and glucose (glucose promotes uptake of the fluid and electrolytes)