Fluid Balance Flashcards
How does aldosterone affect the kidney?
It increases synthesis of Na+ K+ pumps, therefore increasing Na+ reabsorption, water reabsorption (osmosis), blood volume and blood pressure
what are the various parts of the Loop of Henle permeable to?
descending limb is impermeable to solutes, permeable to water (making filtrate very concentrated)
Thin segment of ascending limb is permeable to Na+ and Cl-, poorly permeable to urea, impermeable to water
Allows movement of ions down concentration gradients
Thick segment of ascending loop is impermeable to urea and water
active transport of ions
How is angiotensin II produced?
Juxtaglomerular (granular) cells secrete renin
Renin + angiotensinogen
= angiotensin I
Angiotensin converting enzyme (ACE) converts this to Angiotensin II
How does aldosterone combat low blood pressure?
It increases sodium reabsorption by stimulating the synthesis of sodium pump channel proteins
Increased sodium reabsorption leads to osmotic movement of water into the blood
increased blood volume = increased blood pressure
When and how does ANP combat increased blood pressure?
It is released when cardiac baroreceptor cells detect increased stretch of the right atrium
Inhibits reabsorption of sodium across the collecting duct, leading to less reabsorption of water, decreased blood volume, decreased blood pressure, increased urine volume
Describe the Renin-Angiotensin-Aldosterone Hormone mechanism?
It is initiated under low blood pressure conditions
Juxtaglomerular cells detect reduced stretch of the afferent arterioles and secrete renin
renin + blah blah blah
angiotensin II
vasoconstrictor
increases peripheral resistance and blood pressure
stimulates adrenal gland production of aldosterone and ADH secretion
aldosterone increases synthesis of sodium channel proteins, increases sodium reabsorption and therefore water as well
increased blood volume and increased blood pressure
What occurs as a result of reduced aldosterone secretion?
less sodium is reabsorbed, filtrate osmolality increases, waters ability to move out of filtrate via osmosis is hindered, urine volume increases
urine sodium concentration is increased.
Describe the ADH mechanism
ADH is produced in the supraoptic nucleus in the hypothalamus
ADH is secreted to balance out interstitial fluid and blood osmolality.
ADH is secreted and binds to its receptors on the plasma membrane
G protein mechanism is initiated
Adenylate cyclase converts ATP to cAMP
cAMP encourages aquaporin-2 that contain cytoplasmic vesicles into the apical membrane, these vesicles are permeable to water
Water then moves by osmosis out of the DCT and collecting ducts into the tubule cell
Water exits the tubule cell via aquaporin-3 and 4 vesicles
Blood osmolality decreases, blood volume increases, as does blood pressure.
What detects the changes in osmolality that leads to ADH secretion?
Osmoreceptor cells in the supraoptic nucleus in the hypothalamus
