Excitable Cells Flashcards
what is action potential?
a brief flip flop in polarity across the membrane
why is action potential important?
it is how nerves and muscles contract
how does sodium ions enter the cell?
through facilitated diffusion
why does the cell loose positive charge?
potassium moves out the cell, therefore the cell looses the positive charge
what happens during the depolarizing stage
there is a change in sodium; positive charge is entering the cell
what happens during the repolarizing stage
there is a change in potassium; moves out the cell
what is the threshold
-55
what is the resting membrane potential
-70
what is the peak
+30
is action potential graded or not graded
not graded; meaning all the responses are identical once the threshold is met
what channels open during depolarization
voltage-gated ion channels open so the axon keeps gaining positive charge
when does the refractory period take place
beginning of hyperpolarization
do concentration gradients change during an action potential
the overall concentration gradients for Na+ and K+ do not change during an action potential
is action potential required
nerves have to have action potential in order to function properly
what does absolute refractory mean
the cell cant respond at all
what does relative refractory mean
the cell needs a bigger stimulus then usual to reach threshold
are leaky potassium channels always open ?
yes
what kind of stimulus is needed during the refractory period
a larger stimulus because its farther from threshold
what is the purpose of an inactivation gate
prevents the cell from being stimulated again until you are done with action potential
when do the inactivation gates slide into place
at the peak
what does propagate mean
to make more
where do action potentials take place
in the axon
what is the cell membrane mostly made of
phospholipids
what is the axon covered in
mylein
