Chapter 20: Fluid and Electrolyte Balance Flashcards
What are water and Na+ associated with
extracellular fluid volume and osmolarity
What happens if the osmolarity of the ECF becomes too high?
It decreases the volume and water leaves the cell
What happens when there is a decrease in BP and Blood volume
The kidneys conserve salt and water to minimize further volume loss
What happens if pathological water loss disrupts homeostasis
It can decrease blood pressure which leads to tissues not getting enough oxygen. When too much fluid is lost, solutes are left behind raising the osmolarity and disrupting cell functions
Can kidneys replace water volume?
No, they can only conserve it.
How do the kidneys conserve water
By adjusting the amount of water being reabsorbed from the urine and returned to the bloodstream.
How does the kidney control urine concentration?
By varying the amounts of water and Na+ reabsorbed in the distal nephrons.
Is water lost or gained in the loop of Henle
It is lost, and the filtrate becomes more concentrated
Does the filtrate more or less concentrated in the ascending loop of Henle compared to the descending loop of Henle? Why?
It is less concentrated and more diluted(hypoosmotic). The thicker wall of the ascending loop of Henle means that it is impermeable to water. Salt ions leave the filtrate via active transport and goes into the interstitial fluid.
How do duct cells alter their permeability
By the hormone vasopressin (ADH). When the body is dehydrated, ADH is increased. This tells the duct cells to insert aquaporins. This increases the amount of water exiting the collecting duct and puts it back into the blood. When the body is hydrated, the ADH hormone is reduced, and the duct cells close a couple of their aquaporins. This keeps the fluid inside the collecting ducts to be excreted in urine.
What does high osmolarity mean
It is more concentrated with stuff. More solutes than solvents
What water channel is regulated by vasopressin, and where is it found
AQP2 (the name of the aquaporin in the duct cells). It is found in the tubule lumen and the membrane of cytoplasmic storage vesicles(this is inside a cell)
What happens when vasopressin arrives at the collecting ducts
It binds to V2 receptors activating the G protein/cAMP system
What stimuli control vasopressin secretion? What is the most potent?
Plasma osmolarity, blood pressure, blood volume. Plasma osmolarity is the most potent
Where are osmoreceptors found
In the hypothalamus and carotid sinus of the neck
How are osmoreceptors fired
by shrinking causing the cation channels linked to actin filaments open, depolarizing the cell
What are the vasa recta
It is blood vessels that surround the loop of Henle. The veins are in the descending vasa recta and the arteries in the ascending vasa recta
What structure in the kidney regulates blood flow and blood pressure
the vasa recta
What happens when we consume large amounts of salt?
The osmolarity in the body would increase. This triggers vasopressin to be released and triggers thirst to encourage us to drink water. This decreases osmolarity but increases ECF and blood pressure. Body then triggers pathways to bring BP, and ECF back down by excreting the extra water and salt
What happens when aldosterone is increased?
The level of Na+ reabsorption and K+ secretion is increased
What is the primary target of aldosterone?
Principle cells (P cells)
