Exam #5: Fluid & Electrolytes Flashcards Preview

Medical Physiology > Exam #5: Fluid & Electrolytes > Flashcards

Flashcards in Exam #5: Fluid & Electrolytes Deck (21)
Loading flashcards...
1
Q

Where is Na+ absorbed?

A

Generally, Na+ is absorbed in BOTH the small & large intestine

2
Q

What are the mechanisms of Na+ absorption? Where are these transporters located? When are they primarily functioning?

A

There are four key transport proteins involved in the uptake of Na+:
Jejunum= following a meal
1) SGTL1 (glucose)
2) Amino Acid Transporter B

Jejunum, Ileum, & Proximal Colon= interdigestive period
3) Na+/H+ Exchanger

Colon
4) Na+ channel

*****Note that the basolateral membrane has Na+/K+ ATPase, which keeps Na+ flowing DOWN its concentration gradient

3
Q

Where is Cl- absorbed?

A

Cl- is absorbed in BOTH the small & large intestine

4
Q

What are the mechanisms of Cl- absorption?

A

There are two mechanisms for Cl- absorption:

1) Passive diffusion of Cl- following Na+ & water via a paracellular pathway
2) Cl-/bicarbonate Exchanger i.e. Cl- IN & HCO3- OUT

5
Q

Where is Cl- secreted?

A

asdf

6
Q

What is the mechanism of Cl- secretion?

A

CFTR that is located in the apical membrane of the enterocyte.

*****Note that Na+ follows and causes water to stay in the lumen

7
Q

What regulates the CFTR?

A

Intracellular signaling & accumulation of 2nd messengers result in secretion of Cl- (Na+ follows & water stays in the lumen). Specifically,

1) cAMP opens the CFTR
2) Ca++ opens the CFTR

8
Q

Where is K+ absorbed? Where is K+ secreted?

A

Small intestine= absorption

Large intestine= secretion

9
Q

What are the mechanisms of K+ absorption? What is the mechanism for K+ secretion?

A

Small intestine= “solvent drag”

  • NaCl are absorbed from the gut lumen
  • Water follows & DRAGS K+ with it

Colon= lumen is negative

  • K+ is attracted to the negative lumen & goes the opposite direction
  • result is net secretion
10
Q

What are the signals that regulate electrolyte absorption & secretion?

A

Intracellular signaling & 2nd messenger accumulation i.e. cAMP & Ca++

  • Secretion of Cl- via CFTR opening
  • Inhibit Na+ absorption via Na/H+
  • NET RESULT= NaCl IN LUMEN

Steroids= increase transcription of proteins that generally facilitate Na+ & water uptake

  • Na+/K+ ATPase
  • Na+ Channels
  • Na+/H+ exchanger

Thus,
Intracellular messengers= less water retention
Steroids= retention

11
Q

What are the neuronal pathway & agents that lead to fluid secretion?

A

ACh
VIP
5-HT

**All increase 2nd messengers that stimulate the CFTR & Na+/H+ exchanger

12
Q

What are the paracrine/immune pathway & agents that lead to fluid secretion?

A

Prostalgandin
Histamine

*****Both increase 2nd messengers that stimulate the CFTR & Na+/H+ exchanger

13
Q

What are the bacterial agents that lead to fluid secretion?

A

Cholera toxin
E. coli toxins

*****Both increase 2nd messengers that stimulate the CFTR & Na+/H+ exchanger

14
Q

What are the endocrine mechanisms that promote fluid absorption?

A

Mineralcorticoids
Glucocorticoids

**Both upregulate the transcription of Na+ channels & Na+/K+ ATPase

15
Q

What is the role of somatostatin in fluid absorption?

A

Increased Na+/H+ exchanger leading to fluid absorption

16
Q

What is the difference between osmotic diarrhea and secretory diarrhea?

A

Osmotic= diarrhea caused by a nonabsorbable nutrient

Secretory= diarrhea caused by intestinal secretion of fluid and electrolytes

17
Q

List the causes of osmotic diarrhea.

A
Disaccharide deficieicny 
Pancreatic enzyme def.
Nutrient binding sub. 
Loss of enterocytes 
Bacterial overgrwoth 
Antacids
18
Q

What are the causes of secretory diarrhea?

A

Enterotoxins
Inflammatory cytokines
Tumor

19
Q

What are the causes of both osmotic and secretory diarrhea?

A

Inflammatory conditions

Infectious disease

20
Q

What are the different causes of constipation?

A

1) Diet/ Lifestyle
2) GI
3) Pharmacological
4) Endocrine
5) Neurogenic

21
Q

How do the small & large intestine compare in net absorption & secretion?

A

Small intestine=

  • Absorb: Na+, Cl-, K+ & H2O
  • Secrete: Bicarbonate

Large intestine=

  • Absorb: Na+, Cl-, & H2O
  • Secrete: K+ & Bicarbonate

Thus, the MAIN difference is that K+ is ABSORBED in the small intestine & SECRETED in the large intestine

Decks in Medical Physiology Class (74):