Regulation of Body Fluid Osmolality & Volume

Question 1

Role AVP in regulating body fluid osmolality, outline regulation AVP release

Answer 1

AVP regulates addition water pores (aquaporin 2- AQP2) into apical membrane of CD principal cells
AQP3/4 expressed on basolateral membrane, allow for completion of H2O reabsorption only when AQP2 is expressed

AVP- released by post. pit. in response to:
- high plasma osmolality (osmoreceptors)
- low BP (baroreceptors)
- low BV (baro)
aka Vasopressin, ADH

Question 2

mechanism by which AVP restores normal plasma osmolality and BV/BP in response to disturbances

Answer 2

AVP binds V2R on basolateral surface CD cells
activate GPCR = AC = PKA activation
- protein phosphorylation = AQP2 synthesis/insertion
= increased H2O reabsorption in CD

water restriction = increased plasma osmolality, decreased BV/BP
- stimulate AVP

also stimulation thirst response

Question 3

short and long term response to alc/caffeine intkae

Answer 3

inhibit AVP release

- reduced water reabsorption in CD

Question 4

how JGA responds to changes in BP

Answer 4

Renin secreted from JGA, = increased angiotensin 2
JGA: interface btw glomerulus and maula densa
- reduced BP detected by atrial stretch receptors, and carotid/aortic baroreceptors, = increased SNS innervation of afferent arterioles ALSO, reduced BP is detected directly by arterioesl

Question 5

R-A-A system, role in regulation body fluid volume

Answer 5

liver continually produces angiotensinogen into blood
JGA cells produce renin
renin converts angiotensinogen to angiotensin 1
ACE converts 1 to 2 (found on all vascular endothelial cells, esp in lung)

AG2 has many targets
- includes PT, increases Na+ reabsorption

helps restore H2O volume and BP