IP1: Regulation of Extracellular Fluid Volume and Osmolarity

Question 1

If you drink a large amount of water what happens to osmolarity, volume, urine volume, and sodium excretion?

Answer 1

osmolarity - decrease
volume - increase
Uv - increase
ENa+ - decrease

Question 2

If you drink a hypertonic saline solution what happens to osmolarity, volume, urine volume, and sodium excretion?

Answer 2

osmolarity - increase
volume - increase
Uv - increase
ENa+ - increase

Question 3

If you get dehydrated (sweat, diarrhea) what happens to osmolarity, volume, urine volume, and sodium excretion?

Answer 3

osmolarity - increase
volume - decrease
Uv - decrease
ENa+ - increase

Question 4

If you do not compensate from being dehydrated what happens to osmolarity, volume, urine volume, and sodium excretion?

Answer 4

osmolarity - decrease
volume - decrease
Uv - decrease
ENa+ - decrease

Question 5

What controls both ECF osmolarity and plasma volume?

Answer 5

ADH

Question 6

Decreased plasma volume causes an _______ in ADH

Answer 6

increase

Question 7

Decreased osmolarity causes a _________ in ADH

Answer 7

decrease

Question 8

Is ADH more sensitive to changes in volume or osmolarity?

Answer 8

osmolarity

Question 9

What can cause syndrome of inappropriate ADH?

Answer 9

neurologic disease, head injury, lung tumors, or major surgery

Question 10

What are the symptoms of syndrome of inappropriate ADH (SIADH)?

Answer 10

• excrete a concentrated urine
• too much ADH function

Question 11

What does excessive secretion of ADH cause?

Answer 11

hyponatremia
decreased plasma osmolarity
urine hyperosmolarity

Question 12

What is messed up with syndrome of inappropriate ADH (SIADH)?

Answer 12

• defect is in water excretion
• feedback inhibition of ADH does not occur

Question 13

How do you treat syndrome of inappropriate ADH (SIADH)?

Answer 13

ADH inhibitor drugs (Demeclocycline)

Question 14

What are the symptoms of diabetes insipidus (DI)?

Answer 14

• excrete diulte urine
• too little ADH function
• polyuria
• nocturia
• polydipsia

Question 15

What are the three types of diabetes insipidus?

Answer 15

1. hypothalamic or central (defect in ADH synthesis)
2. nephrogenic (defect in ADH action)
3. polydipsic (compulsive water drinking)

Question 16

What are the three major mechanisms of polyuria?

Answer 16

– Decrease in Na+reabsorption (Kidney Disease, Diuretics)
– Reduced ADH secretion (D.I.)
– ADH resistance

Question 17

What are the four mechanisms of Na+ regulation?

Answer 17

1. Osmoreceptor-ADH
   system.
2. The thirst mechanism
3. Aldosterone and Ang II
   ➢ Alter Na+ mass but NOT conc
   ➢ Changes in Na+ mass accompanied by volume changes (thirst, ADH)
4. Salt Appetite

Question 18

What increases the hypothalamic thirst center?

Answer 18

ECF hyperosmolarity
decreased ECF volume
decreased MAP

Question 19

What hormone acts centrally to increase thirst?

Answer 19

angiotensin II

Question 20

What stimuli increase salt appetite?

Answer 20

• sodium deficits
• decreased blood volume
• decreased blood pressure associated with circulatory insufficiency