Regulation of Osmolarity

Question 1

Water regulation is controlled by?

Answer 1

ADH (antidiuretic hormone) a.k.a Vasopressin

Question 2

Where is ADH synthesised?

Answer 2

Supraoptic (SO) and paraventricular nuclei (PVN) in the hypothalamus

Question 3

How long is the half life of ADH?

Answer 3

Around 10 minutes

Question 4

What stimulates the release of ADH?

Answer 4

Increased oncotic pressure of the plasma
Detected by osmoreceptors in the anterior hypothalamus
Increased discharge of ADH secreting neurons

Question 5

How does maximal ADH secretion produce small volumes of highly concentrated urine?

Answer 5

ADH binds to membrane receptors in the collecting tubules
Activates cAMP secondary messenger
Cell inserts AQP2 water channels into the apical (luminal) membrane
Water absorbed by osmosis into the blood

Question 6

How does the ECF volume affect ADH secretion?

Answer 6

Increased ECF volume = decreased [ADH]

Decreased ECF volume = increased [ADH]

Question 7

What external stimuli can increase ADH secretion?

Answer 7

Pain
Emotion
Stress
Exercise
Nicotine
Morphine

Question 8

What external stimuli can decrease ADH secretion?

Answer 8

Alcohol

Question 9

ADH deficiency is known as?

Answer 9

Diabetes insipidus

Question 10

What causes central diabetes insipidus?

Answer 10

Disease/damage in the ADH synthesising areas

Question 11

What causes peripheral diabetes insipidus?

Answer 11

Collecting ducts that are insensitive to ADH