ECF Volume Regulation

Question 1

What are the major osmoles?

Answer 1

Sodium

Chloride

Question 2

What is the main factor in the regulation of ECF volume?

Answer 2

Regulation of body sodium

Question 3

What is the regulation of sodium dependent on?

Answer 3

High and low P baroreceptors

Question 4

What is the renal response to decreased ECF?

Answer 4

Increase salt and water loss (vomiting, sweating)

Increases sympathetic discharge

Question 5

How does increased salt and water loss increase ECF?

Answer 5

Decreases venous pressure 
Decreases atrial pressure 
Decreases EDV 
Decreases stroke volume 
Decreases cardiac output 
Decreases blood pressure 
Decreases carotid sinus baroreceptor inhibition of sympathetic discharge

Question 6

How does increased sympathetic discharge increase ECF?

Answer 6

Increases VC
Increases TPR
Increases blood pressure towards normal

Question 7

What is the effect of increased sympathetic discharge specifically on the kidney?

Answer 7

Increased renal arteriolar constriction
Increase in renin
Increases angiotensin 2
Decreases peritubular capillary hydrostatic pressure
Increases sodium reabsorption from proximal
Increases aldosterone, increases sodium reabsorption from distal

Question 8

What controls the regulation of distal tubule sodium reabsorption?

Answer 8

Aldosterone

Question 9

What controls aldosterone secretion?

Answer 9

Reflexes involving the kidneys themselves

Question 10

What forms the juxtaglomerular apparatus?

Answer 10

Juxtaglomerular cells

Macula dense of distal tubule

Question 11

What do juxtaglomerular cells produce?

Answer 11

Renin

Question 12

What does renin act on?

Answer 12

Angiotensinogen

Question 13

What controls renin release?

Answer 13

Increased sympathetic nerve activity 
ADH
Angiotensin 2 
Decreases NaCl delivery 
Pressure of afferent arteriole at level of JG cells decreases

Question 14

What is an effect of atrial natriuretic peptide?

Answer 14

Promotes sodium excretion

Question 15

What are the overall effects of aldosterone?

Answer 15

Increases sodium reabsorption
Increases potassium secretion 
Increases weight (Water and Na retention) 
Stimulate ANP release 
Volume expansion

Question 16

What is the course of events leading to a hyperglycaemic coma in uncontrolled DM?

Answer 16

Glucose remains in tubule, exerts osmotic effect to retain water in tubule
Sodium in lumen decreases
Sodium reabsorption will be increased
Decreased ability to reabsorb glucose
Movement of water out of descending limb reduced
Fluid in ascending limb less concentrated