Electrolyte Flashcards
Anions
Negative charge
Cations
Positive charge
Major ECF electrolytes
Sodium
Calcium
Chloride
Bicarbonate
Major ICF electrolytes
Potassium
Magnesium
Phosphates
Negatively charged proteins
Sodium
Major osmole in the plasma
135-145
Potassium
Plays a primary role in maintaining the resting membrane potential of cells
3.5 - 5
Alterations in potassium balance disrupt the function fo excitable cells (nerve and muscle)
Ion channles
Proteins in cell membrane
Maintenance of electrical and chemical balance across the cell membrane
Resting membrane potentials
Determined by the concentration of potassium ion
Expressed thru the Nernst equation for potassium ion
Nernst equation for potassium ion
35 (K+ inside)
——————
1 (K+ outside)
Relationships of potassium ion with H+
Plasma membrane of cells share transport pump for K+ and H+
If ECF is too high in K+, then it is pumped into the cell in exchanged for ICF H+
The reverse can also occur
Relationships of potassium ion with (Insulin and Epinephrine)
Either will increase the activity of the NA+/K+ active transport pump (drives more K+ inside the cell)
Why should insulin always be administered with glucose
To prevent hypoglycemia
What cautions do you have to take with Epinephrine infusion
Increased HR, BP and vasoconstriction
Because of the shared transport proteins for K+ and H+ in the cell membrane
Hyperkalemia creates a risk for acidosis
Acidosis creates a risk for hyperkalemia
How do potassium imbalances alter electrical excitability?
Controls the resting potential Normal 35/1 ratio
35 K+ inside cell
1 K+ outside cell
Hyperkalemia effects
Raises resting potential toward threshold
*increases electrical excitability
When RP reaches Threshold, Na+ gates open and cannot close (CARDIAC ARREST) bc no action potential can be transmitted
Widened QRS
Hypokalemia effects
Lowers resting potential
Decreases electrical excitability
Calcium ion Ca++
Acts as a chemical mediator in coagulation cascade and activation of enzymes
Needed for muscle contraction (actin/myosin binding)
*binds to troponin to more troponin-tropomyosin complex out of the way to uncover myosin for the actin molcule
What does calcium do for electrical excitability of cells
Action potential in Cardiac ventricular muscle
*creates the plateau phase of the action potential in ventricular muscles. It does this by leaking into the cells even while K+ is leaving trying to repolarize
Calcium imbalance
Calcium binds to other stuff so it has two numbers
Total calcium vs ionized (Free) calcium
Ionized : 4.5-5
Total : 8.5-10.5
If either is low = hypocalcemia
If either is high = hypercalcemia
Where is calcium
99% in bones
1% ICF
0.1-0.2 ECF
*50% is free (only one used in metabolic reactions
*10% complexed (bound to neg ions to create chemical compounds)
*40% protein (carrier proteins)
Calcium transport in blood
Calcium and hydrogen compete for binding with carrier proteins (reversible reaction)
Calcium proteinate + hydrogen
Hydrogen proteinate + calcium
Depends which one has more on who binds
Because Ca and H competing this causes what?
Hypercalcemia (serum) creates risk for acidosis (increased H)
*bc the Ca will bind to protein leaving too much Hydrogen in blood
Acidosis (increased H) creates a risk for hypercalcemia (serum)
*bc the H will bind to protein leaving too much Ca in blood
Clinical manifestation of hypocalcemia and hypercalcemia
Hypocalcemia lowers threshold potential
*easier to generate action potential
(tetany of muscles)
Hypercalcemia raises threshold potential
*difficult to generate action potential
(Muscle weakness)
causes : heart and skeletal muscle problems
