fluids and electrolytes

Question 1

fluid compartments

Answer 1

ICF is (cytosol) 60% H2O, ECF 40% (ECF composed of 8% plasma & 32% interstitial fluid)

Question 2

Fluid and electrolyte balance

Answer 2

Hypothalamic thirst centre:
change in osmolarity & plasma volume
Baroreceptor inputs
angiotensin
Feedback mechanisms inhibiting thirst:
Moistening of mucosa
Stretch receptors stomach, intestine
Decrease in osmolarity

Question 3

continued

Answer 3

ADH ↑osmolarity ADH acts to ↑ water reabsorption at CD of kidney= dilute Na+ ↓ osmolarity
Aldosterone – Na+ reabsorbed in the presence of Aldosterone. Coupled with secretion of potassium ions

Question 4

Extracellular fluid loss due to

Answer 4

Low levels of fluid in the ECF
Results in hypernatremia
Cells dehydrate and crenate= impaired cells

Question 5

Hypotonic hydration

Answer 5

high levels of fluid in the ECF
Results in hyponatremia
Cells swell, with lysis possible
Leads to severe metabolic disturbances
Cerebral oedema

Question 6

oedema

Answer 6

abnormal accumulation of fluid in the
interstitial space (ECF becomes hypotonic)
caused by ↑capillary hydrostatic pressure & cap permeability ↓ colloid osmotic pressure
results: impair tissue functioning because of ↑ distance oxygen nutrients and
wastes must diffuse between cells and blood

Question 7

kidneys regulate blood pH

Answer 7

◦ Chemical buffer systems acidic= H ion binding= ↑pH
◦ Respiratory regulation Changes in plasma pH can be altered by a change
in CO2
◦ Renal mechanisms Changes in pH alter renal tubule reabsorption and secretion of H+ ions