Fluid Balance, Electrolytes And Acid Base Balance

Question 1

What is fluid balance ?

Answer 1

Regulation of body water content and distribution within the ECF and ICF

Question 2

What is the percentage of water that makes up total body weight for males, females, elderly and infants

Answer 2

Males: 60%
Females: 50%
Elderly: approx 45%
Infants: 70-80%

Question 3

Why is fluid loss more significant in infants?

Answer 3

They have much more water in the ECF so the fluid is more accessible and can be lost a lot faster.

As most of their body weight is water they don’t need to lose much before having significant abnormalities

Question 4

What is the ratio of fluids in the body

Answer 4

ICF - 66% water
ECF - 33% water
- Interstitial - 75% of ECF
- Plasma - 21% of ECF
- Transcellular - 4% of ECF

Question 5

What is intracellular fluid ?

Answer 5

Fluid inside of the cells which are usually stable and won’t react to fluid changes quickly unless very significant.

Question 6

Why is intracellular fluid important ?

Answer 6

Adequate ICF volume and solute concentration is required to maintain normal bodily processes.
Conditions which influence fluid volume and/or the movement of solutes can significantly impair cellular function leading to tissue damage.

Question 7

What are the 3 components of ECF?

Answer 7

• Interstitial
• Intravascular/plasma
• Transcellular
  All components are much more accessible and more readily affected by external stimulus (changes to fluid, electrolyte and pH disturbances)

Question 8

Where is and what is the role of interstitial fluid?

Answer 8

• Fluid present between the blood vessels and cells
• Facilitate transport of nutrients and waste between the vascular and intracellular spaces
• Transport hormones and neurotransmitters between the cells
• Can accommodate significant changes

Question 9

Intravascular/plasma fluid

Answer 9

• Liquid inside blood vessels which contains a number of organic and inorganic compounds e.g blood cells, proteins, electrolytes, hormones

Question 10

Transcellular fluid

Answer 10

Fluid in specialised places e.g pericardium and synovial joints

Question 11

What is an electrolyte ?
Give an example

Answer 11

A molecule that is ionically bonded and conducts electricity when placed in water as they dissociate into ions. As it dissolves into multiple compounds it increases the number of solutes in a solution
E.g sodium chloride dissociates into a sodium and a chloride

Question 12

Why are electrolytes important?

Answer 12

Play a key role in maintaining and controlling fluid balance.
Increased solutes in fluid increases the osmotic gradient and fluid shift with water.
E.g sodium and chloride has now doubled the strength

Question 13

What are the functions of electrolytes?

Answer 13

• Regulation of minerals and enzymes
• Influences osmosis
• Maintain acid/base balance
• Create action potentials for neurotransmission

Question 14

What are non electrolytes ?
What are some examples?

Answer 14

Compounds that keep their chemical structure when placed in water therefore do not conduct electricity
E.g glucose, oxygen, carbon dioxide, urea, ethanol

Question 15

Where is sodium found and what are the actions?

Answer 15

• Highly concentrated in the blood and interstitial fluids
• Fluid balance, action potentials and muscle contraction

Question 16

Where is potassium found and what are the actions?

Answer 16

• Highly concentrated in the intracellular fluid (in cells)
• Fluid balance, action potential, muscle contraction

Question 17

Where is magnesium found and what are the actions?

Answer 17

• Less prevalent then the rest but mostly in the ICF
• Enzyme activation, muscle contraction, helps maintain Na+ and K balance

Question 18

Where is calcium found and what are the functions ?

Answer 18

Need to do

Question 19

Where is bicarbonate found and what are the actions ?

Answer 19

• Predominantly in the interstitial space and blood
• Buffer system, fluid balance, digestion and acid-base balance

Question 20

What is diffusion ?

Answer 20

Passive process for movement of molecules from a region of high concentration to low concentration. Particles need to be small enough to cross the membrane for diffusion to occur
E.g oxygen, CO2 and water

Question 21

What is facilitated diffusion?

Answer 21

Big molecules that cannot freely cross the membrane require transport proteins to facilitate this movement. This does not require ATP and is passive and is based on a pressure gradient

Question 22

What is active transport ?

Answer 22

Movement of compounds against the gradient requiring ATP and specialised carrier proteins . E.g sodium potassium pump

Question 23

What is the sodium potassium pump?

Answer 23

Sodium continually diffuses into cells which needs to be pumped out in order to maintain osmotic pressure and resting membrane potentials. ATP changes the shape of the pump allowing sodium to be released from the cell. Extracellular potassium then binds to the pump to change the shape back to the original to allow more sodium to bind and be released.

Question 24

What is osmosis?

Answer 24

Movement of water through a semipermeable membrane from a dilute solution to and concentrate solution.
A solution with more solutes will pull water molecules towards it until equilibrium is found

Question 25

What is osmotic pressure ?

Answer 25

Pressure exerted onto water molecules by the presence of solutes. Solution with large number of solutes will draw water towards it and have a strong osmotic pressure

Question 26

What buffer systems are in the ICF and ECF?

Answer 26

ICF - phosphate and protein
ECF - protein and bicarbonate

Question 27

What is bicarbonate buffer system?

Answer 27

Reversible chemical equation
Acidic (remove H+) - hydrogen and bicarbonate bind together to form carbonic acid which breaks down into water and carbon dioxide which is release from the body via exhalation sweat and urine
Alkaline (add H+) - water and carbon dioxide with bind together to create carbonic acid which breaks down into bicarbonate and a hydrogen ion

Question 28

Protein buffer system

Answer 28

Largest buffer system more predominant in ICF. Works by accepting of donating a hydrogen ion.
Acidic - amino groups bind to hydrogen ions removing it from fluid. Once binded no longer active.
Alkaline - carbonyl groups acts as a donor and release the hydrogen ions into the fluid

Question 29

Phosphate buffer system

Answer 29

Primarily active in the ICF and renal tubules. Dihydrogen phosphate is a weak acid
Acidic - H+ and hydrogen phosphate can bind together to form dihydrogen phosphate reducing acidity
Alkaline - Dihydrogen phosphate can break down to form hydrogen phosphate and a free H+ ion

Question 30

What are the four forces involved in starlings law of capillaries

Answer 30

Hydrostatic pressure - blood and interstitial
Osmotic pressure - blood and interstitial

Question 31

What is hydrostatic pressure?

Answer 31

Refers to a pushing/outward pressure therefore is the pressure of fluid that is exerted on its container/enclosed space

Question 32

What is blood hydrostatic pressure?

Answer 32

Pressure exerted by blood on the capillary wall

Question 33

What is osmotic pressure for starlings law of capillaries ?

Answer 33

Pulling/inward pressure determined by osmotic gradients and solute concentrations

Question 34

What is filtration, reabsorption and net filtration pressure?

Answer 34

Filtration - flow out of the capillaries
Reabsorption - flow into the capillaries
NFP - overall movement between the two. If we have more filtration than reabsorption will be a positive NFP. If more reabsorption then filtration it will be a negative NFP.

Question 35

What is the equation for net filtration pressure ?

Answer 35

Blood hydrostatic pressure - blood osmotic pressure = NFP

Question 36

What is third spacing?

Answer 36

Movement of fluid out of the plasma compartment into another compartment/abnormal space usually the transcellular space

Question 37

Why is the sodium potassium pump important ? How is it effected in shock?

Answer 37

Without this pump cells die quickly also important for osmotic pressure and resting membrane potentials
In shock our body doesn’t produce enough atp as we metabolise anarobically therefore this pump can’t work. Sodium draws water into the cell and they pop therefore tissue and organ death occur.