membrane potential Flashcards
(22 cards)
what is membrane potential influenced by?
permeability of important ions
how is membrane potential determined?
1: concentration of ions inside and outside
2: permeability of membrane
3: activity of pumps
is Na high in the intracellular or extracellular environment?
what is its permeability?
extracellular
moderate
is K high in the intracellular or extracellular environment?
what is its permeability?
intracellular
high
what is typical resting potential?
-70mV
what is the ratio of Na to K
3 Na out, 2 K in (inside = more negative)
What equilibrium does K favour?
-90 mV
what equilibrium does Na favour?
60mV
why is the resting potential -70mV and not right in the middle?
K is more permeable so the equilibrium will favour the K side slightly more
what would happen if a bunch of Na channels opened at once?
the equilibrium would be driven closer to Na or more middle
where is the concentration of cl higher?
what is its permeability?
extracellular space
highly permeable
what is cl’s gradient direction?
outward (toward ECF)
what type of cells are nerve and muscle cells?
excitable
what is an excitable cell?
a cell that can change their resting membrane potential to produce electrical signals
what is depolarization?
the net flow of positive ions into the cell (more +). less potential
what is hyperpolarization?
the net flow of positive ions out of the cell (more -) more potential
what is repolarization?
the return to resting potential
what is a graded potential?
a local change in potential
where does graded potential occur?
small, specialized regions of excitable cell membranes
how is the magnitude and length of a graded potential determined?
length and strength of triggering event
why are graded potentials important?
can sum to initiate action potentials
does local current increase or decrease with distance away from the origin?
decrease
