Regulation of Osmolarity Flashcards
Water regulation is controlled by?
ADH (antidiuretic hormone) a.k.a Vasopressin
Where is ADH synthesised?
Supraoptic (SO) and paraventricular nuclei (PVN) in the hypothalamus
How long is the half life of ADH?
Around 10 minutes
What stimulates the release of ADH?
Increased oncotic pressure of the plasma
Detected by osmoreceptors in the anterior hypothalamus
Increased discharge of ADH secreting neurons
How does maximal ADH secretion produce small volumes of highly concentrated urine?
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
How does the ECF volume affect ADH secretion?
Increased ECF volume = decreased [ADH]
Decreased ECF volume = increased [ADH]
What external stimuli can increase ADH secretion?
Pain Emotion Stress Exercise Nicotine Morphine
What external stimuli can decrease ADH secretion?
Alcohol
ADH deficiency is known as?
Diabetes insipidus
What causes central diabetes insipidus?
Disease/damage in the ADH synthesising areas
What causes peripheral diabetes insipidus?
Collecting ducts that are insensitive to ADH