Week 8: Fluids & Electrolytes

electrolyte

• is an ion

• dissociates in water

• ionic compounds

  • inorganic acids (release H+ in water)

  • inorganic bases (release OH- in water)

  • salts (dissociate into cations and anions, not H+ or OH-)

• conducts electricity

non-electrolyte

• organic compounds

  • contain covalent bonds

  • does not dissociate in water

  • bond made by shared electrons cannot be disrupted by water molecules

Na+

• major cation

• extracellular electrolyte

Cl-

• major anion

• extracellular electrolyte

bicarbonate (HCO3-)

• 2nd major anion, major buffer

• extracellular electrolyte

K+

• major cation, followed by Mg2+

• intracellular electrolyte

phosphate

• major anion, buffer

• intracellular electrolyte

acid

• dissociates in water and release H+

• responsible for sour taste of foods

• Strong ____ completely dissociate, releasing large numbers of H+

• weak ____ only partially dissociate, releasing small numbers of H+

base

• substance that can accept hydrogen ion, removing H+ from solution

• strong and weak!

pH

• measure of concentration of H+ per litre of solution, inverse logarithmic scale ranging from 0 - 14.

• each change in 1 value represents a 10-fold change

salts

• electrolyte, held by ionic bond

• dissociates in water but does not release protons nor proton electors

neutralization reaction

• acids and bases react to form salts and water

• HCl + KOH → KCl + H2O

buffer system

solution which resists a change in pH despite addition of acids and bases

• contains a weak acid & weak base that does not react w/ each other, but reacts w/ an added acid or base

• eg. carbonic acid-bicarbonate system

• acid component releases H+ when base is added

• base component absorbs H+ when acid is added

acidosis

• pH < 7.35, CNS depression → coma → death

respiratory acidosis

• impaired ventilation of the lungs (removal of CO2)

• increased pCO2 in the blood

  • asthma

  • emphysema

  • barbiturate poisoning

  • damage of the brain stem

  • damage to respiratory muscles

metabolic acidosis

• increase in acids

• increase in H+ or reduced bicarbonate ions in blood

  • increased production of acids

    • lactic acidosis: strenuous exercise, hypoxia

    • ketoacidosis: starvation, uncontrolled diabetes mellitus

  • severe bicarbonate loss: chronic diarrhea

  • decreased renal excretion of H+: kidney diseases

alkalosis

• pH > 7.45

• overexcitability of CNS

respiratory alkalosis

• decreased pCO2 in blood

  • hyperventilation:

    • high altitudes, anxiety/stress, pain, aspirin overdose

metabolic alkalosis

• increased bicarbonate ions in blood

  • loss of acids: excessive vomiting (loss gastric HCl)

  • excessive intake of alkaline drugs: antaacid