Chapter 20: Fluid and Electrolyte Balance

Question 1

What are water and Na+ associated with

Answer 1

extracellular fluid volume and osmolarity

Question 2

What happens if the osmolarity of the ECF becomes too high?

Answer 2

It decreases the volume and water leaves the cell

Question 3

What happens when there is a decrease in BP and Blood volume

Answer 3

The kidneys conserve salt and water to minimize further volume loss

Question 4

What happens if pathological water loss disrupts homeostasis

Answer 4

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

Question 5

Can kidneys replace water volume?

Answer 5

No, they can only conserve it.

Question 6

How do the kidneys conserve water

Answer 6

By adjusting the amount of water being reabsorbed from the urine and returned to the bloodstream.

Question 7

How does the kidney control urine concentration?

Answer 7

By varying the amounts of water and Na+ reabsorbed in the distal nephrons.

Question 8

Is water lost or gained in the loop of Henle

Answer 8

It is lost, and the filtrate becomes more concentrated

Question 9

Does the filtrate more or less concentrated in the ascending loop of Henle compared to the descending loop of Henle? Why?

Answer 9

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.

Question 10

How do duct cells alter their permeability

Answer 10

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.

Question 11

What does high osmolarity mean

Answer 11

It is more concentrated with stuff. More solutes than solvents

Question 12

What water channel is regulated by vasopressin, and where is it found

Answer 12

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)

Question 13

What happens when vasopressin arrives at the collecting ducts

Answer 13

It binds to V2 receptors activating the G protein/cAMP system

Question 14

What stimuli control vasopressin secretion? What is the most potent?

Answer 14

Plasma osmolarity, blood pressure, blood volume. Plasma osmolarity is the most potent

Question 15

Where are osmoreceptors found

Answer 15

In the hypothalamus and carotid sinus of the neck

Question 16

How are osmoreceptors fired

Answer 16

by shrinking causing the cation channels linked to actin filaments open, depolarizing the cell

Question 17

What are the vasa recta

Answer 17

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

Question 18

What structure in the kidney regulates blood flow and blood pressure

Answer 18

the vasa recta

Question 19

What happens when we consume large amounts of salt?

Answer 19

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

Question 20

What happens when aldosterone is increased?

Answer 20

The level of Na+ reabsorption and K+ secretion is increased

Question 21

What is the primary target of aldosterone?

Answer 21

Principle cells (P cells)