Question

essay on fluid and electrolytes

Answer 1

# Fluid

Water that contains dissolved or suspended substances such as glucose, mineral salts, and proteins

# Overall different fluid compartments

Extracellular fluid

Intracellular fluid

# Extracellular fluid divisions (1/3 )

Intravascular Fluid

Interstitial Fluid

Transcellular Fluid

# Intravascular fluid ( 2/3)

The liquid portion of blood

# Interstitial fluid

Fluid located between the cells and outside the blood vessels

# Transcellular fluid

Fluid secreted by epithelial cells

Examples of transcellular fluid

-Cerbrospinal fluid

-Pleural Fluid

-Peritoneal Fluid

-Synovial Fluid

# Electrolytes are compounds that separate into ions when dissolved in water

Fluid compartments

ECF:

- cations: Sodium & potassium

- anions: Chloride, bicarbonate, proteins

ICF:

- cations: Potassium, magnesium, sodium

- anions: Phosphate, proteins, bicarbonate

# Fluid balance

Important because cells are totally dependent on water

Regulated by daily intake (food & drink) & loss (urine, faeces, breath)

# Electrolyte Balance

Important because many cell functions depend on electrolytes

Regulated by daily intake (food & drink) & loss (urine, faeces, breath)

To stay in balance the intake of each electrolyte has to be equal to its loss

# Fluid movement within the ECF

Net hydrostatic pressure:

- pushes water out of plasma

- into interstitial fluid

Net osmotic pressure (from dissolved compunds)

- draws water out of interstitial fluid

- into plasma

- an osmotic gradient between the ECF & ICF will make water move (this is called "fluid shift")

# Water loss

Dehydration occurs when the water intake is less than the loss

The body responds to waterloss with homeostatic responses

- physiological mechanisms (ADH & renin secretion)

- behavioural changes (> fluid intake)

# Fluid movement

Allocation of water losses: If water is lost, but electrolytes retained

- ECF osmotic concentration rises

- water moves from ICF to ECF

- net change in ECF is small

# Basic concepts: fluid & water regulation

Homeostatic & regulatory mechanisms monitor the composition of the ECF (eg. blood & CSF) and not the ICF (cells)

NO receptors directly monitor fluid or electrolyte balance (its plasma volume & osmotiv concentration that is monitored)

Active transport CANNOT move water molecules (however "water follows salt" so moving electrolytes can indirectly move water)

Water intake/loss & electrolyte intake/loss must balance. Feedback mechanisms aim to maintain the right balance

Electrolyte balance rules

Most common electrolyte balance problems in the body are caused by an imbalance in gains & losses of sodium &/or potassium &/or calcium ions

Of these, an Na ion imbalance is most common (but K is more dangerous)

Electrolyte balance

Sodium:

- is the dominant cation in the bodies ECF

- sodium salts, sodium chloride & sodium bicarbonate provide 90% of ECF osmotic pressure

Sodium balance:

- sodium ion uptake accross digestive epithelium

- sodium ion excretion in urine & perspiration