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13 Cards in this Set

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  • Back

Fluid Compartments: ICF and ECF

ICF: largest and 67% of body weight

ECF: Plasma (3L- all of blood minus WBC) and Interstitial Fluid (surrounds all of the tissues, cells in our bodies)


- all solutes dissolved in plasma water plus large solutes such as proteins

-water, number of different electrolytes, cations and anions (sodium, bicarbonate, chloride), glucose

-Cl- is the largest anion and proteins are also negatively charged

- Water is the largest constituent

- The major cation in plasma, ICF and ECF include K+, Na+ and Ca+



Sodium (ECF high), Potassium (ICF high) , Calcium and Magnesium


Chloride (ECF high) , Bicarbonate, Protein (ICF) Phosphate (ICF) and Sulfate


Measure the potential inside a cell- is it important to have the same number of positive and negative charges - THE CHARGE IS WHAT MATTERS!!!!!!

Osmotic Equilibrium

- ECF =isotonic

-no net movement of water from one compartment to the next

- ECF AND ICF in Osmotic Equilibrium as the cell do not change in volume BUT THEY ARE IN CHEMICAL DISEQUILIBRIUM (cation and anion different distribution between ICF and ECF) and ELECTRICAL DISEQUILIBRIUM

- Glucose is HIGH in ECF than ICF

Permeability/ Phospholipid Bilayer Membrane

-Physical barrier

- Lipid Soluble, SMALL enough to go through

- Diffusion (down concentration gradient)

-Steroid and Thyroid Hormones, Nitric Oxides (gases-paracrine molecule and neurotransmitter), CO2 and O2

-all gases can pass through

Membrane Potential Difference

-electrical disequilibrium between compartments

-Inside of the cell is MORE NEGATIVE than the outside of the cell

- The resting membrane potential is -70mV,

- ECF potential = 0

Will this continue forever until there is 75 mM across the membrane?


- as the potassium ion comes out, separation of charge is created making OUTSIDE MORE POSITIVE and INSIDE MORE NEGATIVE, no net flux

- concentration gradient acts as chemical force that pushes K+ out of the cell

- An electrical force is set up that opposes the chemical force

Equilibrium Potential

- -90mV (K+)

- 60mV (Na+)

Nerst Potential

- Equilibrium Potential

- applies to ONLY 1 ion that is PERMEABLE to the membrane

-Resting Membrane is NOT equal to Equilibrium Potential for Potassium

Resting Membrane Potential

- -70 mV

- Magnitude depends on:

--> difference in different ion concentrations between ICF and ECF

--> differences in membrane permeability to different ions

- At rest, permeability to K+ atleast 40X higher than permeability to Na+ ions

-Resting membrane potential is MUCH CLOSER to the K+ Equilibrium Potential

- If neurons were only permeable to K+, resting membrane potential = K+ potential

- for it to = -70 mV, has to be permeable to Na+ and K+ ion, has to have active Na+-K+ ATPase pump, without the pump, membrane potential goes to

Membrane Proteins

transporters or receptors