Lecture 14: Fluid balance

Question 1

What are the 6 major functions of the kidney?

Answer 1

1. Metabolic waste excretion
2. Endocrine functions
3. Drug metabolism/excretion
4. Control of solutes and fluid status
5. Blood pressure control
6. Acid/base

Question 2

If the fluids cannot be excreted by the kidneys where is the first place this excess fluid ends up and what does it cause?

Answer 2

It accumulates in the lungs causing acute pulmonary oedema (fluid on the lungs) or accumulates in the peripheral vascular tissues causing peripheral oedema

Question 3

What is the main complication for hyperkalaemia?

Answer 3

hyperkalaemia= high potassium

The main complication is cardiac arrhythmias such as ventricular fibrillation. These can be fatal.

Question 4

What percentage of total body fluids is located intracellularly at any period of time?

Answer 4

2/3rd of total body fluids (67%)

Question 5

What percentage of total body fluids is located extracellularly at any period of time?

Answer 5

Extracellular: intravascular + interstitium

1/3 of the total body fluid (33%)

Question 6

Potassium concentration is high in which body fluid compartment?

Answer 6

Intracellular

Question 7

Sodium and chloride concentration is high in which body fluid compartment?

Answer 7

Interstitium

Question 8

Potassium is found in high levels intracellularly. Which organ/compartment contains the most potassium?

Answer 8

Muscle!!!

Question 9

The majority of the body fluids are located in which body compartment

Answer 9

Intracellular- 2/3rds

Question 10

Within cells the principle cation is ?

Answer 10

Potassium

Question 11

The majority of the extracellular fluid is located where?

Answer 11

In the intersitium

Question 12

Within the extracellula the principle cation is?

Answer 12

Sodium

Question 13

What are the 3 fluid compartments of the body?

Answer 13

• Intracellular
• Extracellular
  
  • Interstitium
  • Intravascular

Question 14

The majority of work of kidney is undertaken in which part?

Answer 14

The cortex

Question 15

Name these parts of the nephron

Answer 15

Question 16

Describe the glomerular filtration barrier

Answer 16

• Endothelium is fenestrated so allows only small molecules to travel through.
• Afterwhich, the molecules are meet by the glomerular basement membrane, which is negatively charged therefore rejecting the proteins (remember proteins are negatively charged).
• Podocytes is the last layer which also inhibits the passage of large molecules

Question 17

Podocyte foot processes forming ___ effect

Answer 17

Zipper - interlocking fingers.

Question 18

What percetnage of filtrates are reabsorbed

Answer 18

99%

Question 19

What is the cell to lumen side called?

Answer 19

Luminal or apical

Question 20

What is the cell to interstitium/capillary side called?

Answer 20

Basolateral

Question 21

Define osmolality?

Answer 21

The concentration of osmole per unit mass

Question 22

Define osmolarity

Answer 22

The concentration of osmole per unit volume

Question 23

The 3Na-2K-ATPase pumps out intercellular Na+ ions on the ___ side of the cells in the PCT

Answer 23

Basolateral

Question 24

What are the main two channels in the proximal convoluting tubule

Answer 24

Potassium/Sodium exchanger

Sodium/Hydrogen antiporter

Question 25

How long is the proximal convoluted tubule

Answer 25

14mm

Question 26

Water follows?

Answer 26

Sodium

Question 27

Thick ascending limb is impermeable to _____, but actively transports ____.

Answer 27

Thick ascending limb is impermeable to water, but actively transports sodium, potassium and chloride

Question 28

The thin descending limb is freely permeable to?

Answer 28

Salt and water

Question 29

Describe the countercurrent exchange

Answer 29

• The vasa recta are highly permeable and does not wash the gradient.
• The medulla (the location of the loop) is highly salty (high sodium chloride concentration).
• As the fluid moves down the descending limb, water moves out due to osmotic pressure (as the surround liquid is highly salty). As the descending limb is impermeable to solutes the osmolality increases.
• The ascending limb is permeable to sodium and chloride and impermeable to water. The high osmolar fluid enters the ascending limb and the solutes move out into the surrounding medulla.

Question 30

Which channel is important in the thick ascending limb

Answer 30

NKCC 2 channel

Causes the uptake of sodium, chloride and potassium.

Potassium is put back into the lumen by the ROMK channel

Question 31

Which channel in the thick ascending limb causes the sodium chloride reabsorption

Answer 31

NKCC2

Question 32

Sodium is reabsorbed by which channel is the distal convoluted tubule

Answer 32

NCC

Reabsorbs in sodium and chloride

Question 33

Aldosterone stimulates which receptors stimulating sodium reabsorption?

Answer 33

ENaC

Question 34

Aldosterone stimulates which receptor to cause the excretion of potassium?

Answer 34

ROMK

Question 35

NaK ATPase / NaH antiporter are located where in the nephron

Answer 35

Proximal convoluting tubule

Question 36

NKCC2 receptor is located where?

Answer 36

In the thick ascending loop of Henle

Question 37

NCC receptor is located where in the nephron?

Answer 37

In the distal convoluting tubule

Question 38

ENaC receptor is located where in the nephron

Answer 38

Collecting duct on principal cells

Question 39

Describe the rebasorption and secretion of the urea?

Answer 39

Urea is freely filtered at the glomerulus

It is reabsorbed in the collecting ducts

Question 40

Define the term natruiresis

Answer 40

Eexcretion of sodium in the urine.

Question 41

Defne the term hyponatraemia

Answer 41

Low plasma sodium level