Control Of Extracellular Fluid II

Question 1

What is a volume contraction?

Answer 1

A decrease in ECF volume

Question 2

What is a volume expansion?

Answer 2

Increase in ECF volume

Question 3

When a volume expansion/contraction is called isosmotic, hyperosmotic, or hyposmotic, what do those terms refer to?

Answer 3

The resulting osmolarity of the ECF

Question 4

What is diabetes insipidus?

Answer 4

You either can’t make ADH or your kidneys cant respond to it

=losing too much water in urine

Question 5

How will diabetes insipidus affect:

Plasma osmolarity

Urine osmolarity

Amount of urine

Thirst

Answer 5

Plasma osmolarity: High (very concentrated blood)

Urine osmolarity: Low (very watery)

Polyuria

Excessive thirst due to hyperosmotic plasma

Question 6

What are the 2 types of diabetes insipidus?

Answer 6

1. Neurogenic- pituitary gland can’t make ADH. Plasma ADH will be low.
2. Nephrogenic- kidney unable to respond to ADH. Plasma ADH is high** since pituitary is functioning normally

Question 7

Which kind of diabetes insipidus will be helped by the administration of an exogenous ADH agonist like Desmopressin

Answer 7

Neurogenic

Nephrogenic D.I. Will not respond

Question 8

What kind of expansion/contraction will eating a large amount of salt have?

Answer 8

Hyperosmotic Volume Expansion

Question 9

What kind of volume expansion/contraction will drinking a ton of water cause?

Answer 9

Hyposmotic Volume Expansion

Question 10

What kind of a volume expansion/contraction will SIADH cause?

(Syndrome of inappropriate ADH secretion)

Answer 10

Hyposmotic Volume Expansion

Not ~always~ a big volume expansion, but you will be VERY hyponatremic

Question 11

What happens to your ECF osmolarity and your sodium levels if you have SIADH?

Answer 11

Your ECF will be very diluted

You will be VERY hyponatremic**

Question 12

Why will you be so hyponatremic if you have SIADH?

Answer 12

Excessive renal sodium loss due to decreased aldosterone and increased ANP

Question 13

Will you have hypertension if you have SIADH?

Answer 13

No

Question 14

What kinds of things can cause SIADH?

Answer 14

Head injury

Lung tumors that secrete ADH

Question 15

What is the major cation of the ECF, and thus determines the volume of ECF compartment?

Answer 15

Na+

Question 16

True or false:

Na+ loss through diarrhea or vomiting is isotonic

Answer 16

True

Question 17

Which has more of an effect on the osmolarity of the ECF:

Changes in Na+ content or changes in water content

Answer 17

Changes in water content

Question 18

What are common causes of hyponatremia?

Answer 18

1. Hemmorhage
2. Excessive water conservation (SIADH)
3. Excessive water intake

Question 19

Why would hemmorhage cause hyponatremia?

Answer 19

The low plasma volume will activate ADH which will cause increased water reabsorption, and will cause thirst.

(Hemorrhage patients will beg for water, but make sure you give them salt water)

Question 20

How come hypernatremia is not much of a problem?

Answer 20

Because you will get really thirsty and just drink water which will quickly dilute the plasma sodium