PROPAGATION OF THE ACTION POTENTIAL

Resting potential is

The electric potential difference between the interior and exterior of the cell when the cell is physiologically at rest

For different types of cells the resting potential varies

from -50 mV to -100 mV

The internal membrane surface

carries negative charge relative to the external surface

To measure the resting potential, it requires two microelectrodes. They must be located

probe is inserted in the cytoplasm and reference is placed in the surrounding fluid

According to the Bernstein's hypothesis

the resting potential is the equilibrium potential for the potassium ion

According to the Hodgkin-Katz theory

the resting potential is the potential of a steady state, not of an equilibrium state

According to the Hodgkin-Katz theory

the resting potential is the net result of the fluxes of potassium, sodium, chloride, and other ions across the membrane

The total charge flux density is

the sum of the flux densities of the cations minus the sum of the flux densities of the anions

The flux density J is positive when

the ions move into the cell

The concentration gradient

points chlorine ions from the cell outwards

According to the Bernstein's hypothesis

the cell membrane is permeable to potassium ions

The flux density J is proportional to

the permeability of the membrane P, and the driving force X

In the resting membrane

some potassium channels are open and the permeability to potassium is relatively large

In the resting membrane

the sodium channels are closed and the permeability to sodium is very small

The concentration and electric potential gradients

move potassium ions in opposite directions

The concentration and electric potential gradients

move sodium ions in the same direction

Steady state can be established when

the potassium and sodium fluxes are equal and opposite to each other

The resting potential of almost all cell membranes

can be correctly calculated with the Goldman equation if appropriate permeability values are used

The strongest contribution to the resting potential is from

the ion with the highest membrane permeability

The flux of potassium ions across the membrane

increases the absolute value of the resting potential (makes it more negative)

The flux of sodium ions across the membrane

decreases the absolute value of the resting potential (makes it less negative)

The concentrations of ions in the extracellular fluid are

the same for all human tissues;

The concentrations of ions in the intracellular fluid are

almost the same in all human cells

The resting potential of various types of cells is

different because their membranes have different permeabilities

The sodium-potassium ion pump makes the electric potential inside the cell

more negative

The net positive charge flux due to the sodium-potassium ion pump

is directed outwards from the cell

The permeability of the membrane to all ions of damaged cells

increases (the transport processes become less specific)

The resting potential of damaged cells

decreases by absolute value (become less negative)