Regulation of osmolarity

Question 1

Where is ADH synthesised?

Answer 1

Magnocellular neurons in the hypothalamus

Question 2

Where is ADH secreted?

Answer 2

Posterior pituitary

Question 3

When osmoreceptors detect an increase in the OP, what happens to ADH secretion?

Answer 3

Increased ADH production

Question 4

What happens to ADH secretion when osmolarity decreases?

Answer 4

Decreased

Question 5

What is the difference between osmolarity & tonicity

Answer 5

Molecules which can penetrate the membrane along with water do not produce tonicity but affect osmolarity.
Impermeable molecules affect tonicity

Question 6

What is urea?

Answer 6

Ineffective osmole

Question 7

Does urea change the osmolarity?

Answer 7

Yes

Question 8

What increases the permeability of collecting ducts to water? How?

Answer 8

ADH

Aquaporins

Question 9

If maximal ADH is produced, how concentrated will the urine become?

Answer 9

1200mOsm

Question 10

With maximal ADH, what urine will be produced?

Answer 10

Small concentrated urine

Question 11

In the absence of ADH, what is the concentration of urine?

Answer 11

100mOsm

30-50 due to more ion reabsorption

Question 12

Is the CD permeable or impermeable to water in the absence of ADH?

Answer 12

Impermeable

Question 13

Are CD permeable to urea?

Answer 13

Yes

Question 14

What enhances the CD permeability to urea?

Answer 14

ADH

Question 15

In antidiuresis, what will happen to urea levels? What does it do

Answer 15

Reabsorb urea

Acts to reinforce the medullary interstitial gradient

Question 16

Why is it important that urea can be recycled during antiduiresis?

Answer 16

It has an osmotic effect therefore would draw water into CD

Question 17

When ECF increases, what happens to ADH secretion?

Answer 17

Decreases

Question 18

When ECF decreases, what happens to ADH secretion?

Answer 18

Increases

Question 19

Where are low P receptors found?

Answer 19

R & L atria & great veins

Question 20

Where are the High P receptors found?

Answer 20

Carotid & aortic arch baroreceptors

Question 21

What normally tonically inhibits ADH secretion?

Answer 21

Vagus nerve

Question 22

What affect does orthostatic hypotension have on ADH secretion?

Answer 22

Increases ADH

Question 23

What stimulates increase in ADH production?

Answer 23

Exercise
Stress
Nicotine
Pain
Emotion

Question 24

What decreases ADH secretion?

Answer 24

Alcohol

Question 25

What are the 3 main stimuli which promote ADH secretion?

Answer 25

Low P receptors
High P receptors
Osmoreceptors

Question 26

What condition demonstrates ADH deficiency?

Answer 26

Diabetes Insipidus

Question 27

What could be a primary cause of DI?

Answer 27

Tumour or trauma to hypothalamus

Question 28

What could cause secondary DI?

Answer 28

Insensitivity of CD to ADH

Question 29

What symptoms are experienced with DI?

Answer 29

Thirst
Drink large amounts of water
Large volume of dilute urine

Question 30

How can central DI be treated?

Answer 30

Administer ADH