Physiology 3120 Lecture Notes - Lecture 8: Alkalosis, Respiratory Acidosis, Cotransporter

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Woods Lecture 8
*only need to know combination for dehydration*  otherwise will only ask to go into details
for changes in osmolarity OR changes in volume but not various combinations of both
1. Increase blood volume + decrease blood osmolarity  by drinking large amount of water
-blood volume increase increases BP detected by baroreceptors and blood osmolarity decrease
detected by very sensitive osmoreceptors
2. Increase blood volume + no change in blood osmolarity  by drinking isotonic saline
3. Increase blood volume + increase blood osmolarity  by drinking large amount of hypertonic
saline
4. No change in blood volume + decrease blood osmolarity  by replacing sweat with plain
water
5. No change in blood volume + increase blood osmolarity  by eating salt without drinking
water
6. Decrease blood volume + decrease blood osmolarity  by not compensating for dehydration
7. Decrease blood volume + no change in blood osmolarity  by hemorrhage
8. Decrease blood volume + increase blood osmolarity  by dehydration due to sweat loss or
diarrhea
-blood volume decrease decreases BP detected by baroreceptors and blood osmolarity increase
detected by very sensitive osmoreceptors
-sweat is hypoosmotic thus contains less ions than the blood it is coming from
-this decreases ECF volume but increases plasma osmolarity (since not many ions leaving)
Decrease in ECF Volume
-volume receptors and baroreceptors detect low volume/low BP causes renin release 
activates RAAS pathway
-AngII hormone released from kidney into bloodstream to get to adrenal cortex to stimulate
aldosterone release AND AngII triggers ADH release from posterior pituitary gland (see Woods
L7)
-AngII acts on proximal tubule and aldosterone acts on collecting duct
-sodium reabsorption increases and water follows to bring ECF volume back up
-decrease in ECF volume also triggers ADH release from posterior pituitary gland for max ADH
release
Increase in ECF Volume
-osmoreceptors shrink to trigger ADH release from posterior pituitary gland
-water reabsorption increases
BUT plasma osmolarity has increased so WHY are we increasing Na reabsorption?
-because this way achieves max water reabsorption and in the case of dehydration, body more
concerned about maintaining water balance than osmolarity
-once ECF volume back to normal levels, negative feedback sent to stop RAAS activation and Na
reabsorption
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