10.17 Action Potential Flashcards
can action potentials be summed?
no
the inactivation of VG Na+ channels is voltage ____________ while the release of that inactivation is voltage ___________
independent
dependent
action potentials have what three properties as compared to graded potentials?
they are always depolarizing
can’t be summed
their conduction is non-decremental
what are the two factors that increase the speed of an action potential?
axon diameter
myelination
graded potentials have what three properties?
they can be summed
they decrease decrementally
they can be hyperpolarizing or depolarizing
the __________ the diameter of the axon, the faster the propagation speed
larger
when the voltage drops to a specific level, the inactivated VG Na+ channels become ________ but not __________. The length of this time defines the:
closed but not inactivated
absolute refractory period
what is the period called where a second action potential can’t be excited no matter how large the stimulus is that is applied
why does this happen?
absolute refractory period
there aren’t enough VG Na+ channels available to make the depolarization needed for an action potential
what causes the hyperpolarization seen at the end of an action potential?
the late opening of VG K+ channels
what is the period called when it is possible to elicit an action potential but it requires a larger than normal stimulus?
relative refractory period
Guillan-Barre is a loss of myelination in the _________ nervous system
peripheral
what two things define this relative refractory period?
how long it takes for the VG K+ channels to close. when these are open, it takes a larger than normal stimulus to depolarize the membrane to threshold
period after a.p. where some channels are available and some are not. during this, it takes a larger than normal stimulus to recruit the necessary number of channels since there are less of them
during action potential propagation, the flow of current between two action potentials is ________
electrotonic
why do we not get an action potential in the part of the axon where it originally came from?
refractory period of VG Na+ channels
what begins repolarization of the membrane potential during an action potential?
inactivation of VG Na+ channels