Lecture 6 Regulation of Osmolarity Flashcards
What controls water regulation
ADG (vasopressin)
Where is ADH synthesised
supraoptic (SO) and paraventricular (PVN) nuclei of the hypothalamus in the brain
Why does the ingestion of hypertonic solutions such as seawater cause dehydration
Increases the solute load to be excreted and increase in urine flow because ore H2O is required to excrete the solute load
Describe the mechanism of ADH (vasopressin)
- Vasopressin binds to membrane receptor
- Receptor activates cAMP second messenger system
- Cell insert AQP2 water pores into apical membrane
- water is absorbed by osmosis init the blood
In terms of ADH Water deficit triggers
maximal ADH to produce a small volume of highly concentrated urine
In term of ADH Water excess triggers
Absence of ADH
Collecting ducts are impermeable to H2O
Large volume of dilute urine is excreted
What is the role of urea in the production of concentrated urine
In anti-diuresis with high levels of ADH, urea is retained in order to save water and reinforce medullary interstitial gradient in region of thin ascending limb of LOH
Why is it important that urea is reabsorbed from the tubule
If it remained in the tubule it would exert an osmotic effect to hold H2O in the tubule –> dehydration
if there is an increase in ECF how does that effect ADH
Decreases
If there is an decrease in ECF how does that effect ADH
Increases
What are Low P receptors and where are they located
Located in the L and R atria and great veins
– decrease in ECF volume –> decrease in atrial receptor discharge and increase in ADH release
What are high P receptors and where are they found
Located in the carotid and aortic arch baroreceptors
– Volume changes enough to affect mean blood pressure and ADH secretion
What causes an increase in ADH
Pain, emotion, stress, exercise, nicotine, morphine. Following traumatic surgery
What decreases ADH
Alcohol–> very dilute large amounts of urine
What are the types of diabetes insidious
Central and Peripheral
