Fluid Balance, Electrolytes And Acid Base Balance Flashcards
What is fluid balance ?
Regulation of body water content and distribution within the ECF and ICF
What is the percentage of water that makes up total body weight for males, females, elderly and infants
Males: 60%
Females: 50%
Elderly: approx 45%
Infants: 70-80%
Why is fluid loss more significant in infants?
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
What is the ratio of fluids in the body
ICF - 66% water
ECF - 33% water
- Interstitial - 75% of ECF
- Plasma - 21% of ECF
- Transcellular - 4% of ECF
What is intracellular fluid ?
Fluid inside of the cells which are usually stable and won’t react to fluid changes quickly unless very significant.
Why is intracellular fluid important ?
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.
What are the 3 components of ECF?
- Interstitial
- Intravascular/plasma
- Transcellular
All components are much more accessible and more readily affected by external stimulus (changes to fluid, electrolyte and pH disturbances)
Where is and what is the role of interstitial fluid?
- 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
Intravascular/plasma fluid
- Liquid inside blood vessels which contains a number of organic and inorganic compounds e.g blood cells, proteins, electrolytes, hormones
Transcellular fluid
Fluid in specialised places e.g pericardium and synovial joints
What is an electrolyte ?
Give an example
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
Why are electrolytes important?
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
What are the functions of electrolytes?
- Regulation of minerals and enzymes
- Influences osmosis
- Maintain acid/base balance
- Create action potentials for neurotransmission
What are non electrolytes ?
What are some examples?
Compounds that keep their chemical structure when placed in water therefore do not conduct electricity
E.g glucose, oxygen, carbon dioxide, urea, ethanol
Where is sodium found and what are the actions?
- Highly concentrated in the blood and interstitial fluids
- Fluid balance, action potentials and muscle contraction
Where is potassium found and what are the actions?
- Highly concentrated in the intracellular fluid (in cells)
- Fluid balance, action potential, muscle contraction
Where is magnesium found and what are the actions?
- Less prevalent then the rest but mostly in the ICF
- Enzyme activation, muscle contraction, helps maintain Na+ and K balance
Where is calcium found and what are the functions ?
Need to do
Where is bicarbonate found and what are the actions ?
- Predominantly in the interstitial space and blood
- Buffer system, fluid balance, digestion and acid-base balance
What is diffusion ?
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
What is facilitated diffusion?
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
What is active transport ?
Movement of compounds against the gradient requiring ATP and specialised carrier proteins . E.g sodium potassium pump
What is the sodium potassium pump?
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.
What is osmosis?
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
What is osmotic pressure ?
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
What buffer systems are in the ICF and ECF?
ICF - phosphate and protein
ECF - protein and bicarbonate
What is bicarbonate buffer system?
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
Protein buffer system
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
Phosphate buffer system
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
What are the four forces involved in starlings law of capillaries
Hydrostatic pressure - blood and interstitial
Osmotic pressure - blood and interstitial
What is hydrostatic pressure?
Refers to a pushing/outward pressure therefore is the pressure of fluid that is exerted on its container/enclosed space
What is blood hydrostatic pressure?
Pressure exerted by blood on the capillary wall
What is osmotic pressure for starlings law of capillaries ?
Pulling/inward pressure determined by osmotic gradients and solute concentrations
What is filtration, reabsorption and net filtration pressure?
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.
What is the equation for net filtration pressure ?
Blood hydrostatic pressure - blood osmotic pressure = NFP
What is third spacing?
Movement of fluid out of the plasma compartment into another compartment/abnormal space usually the transcellular space
Why is the sodium potassium pump important ? How is it effected in shock?
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.
