10.17 Action Potential

Question 1

can action potentials be summed?

Answer 1

no

Question 2

the inactivation of VG Na+ channels is voltage ____________ while the release of that inactivation is voltage ___________

Answer 2

independent

dependent

Question 3

action potentials have what three properties as compared to graded potentials?

Answer 3

they are always depolarizing
can’t be summed
their conduction is non-decremental

Question 4

what are the two factors that increase the speed of an action potential?

Answer 4

axon diameter

myelination

Question 5

graded potentials have what three properties?

Answer 5

they can be summed
they decrease decrementally
they can be hyperpolarizing or depolarizing

Question 6

the __________ the diameter of the axon, the faster the propagation speed

Answer 6

larger

Question 7

when the voltage drops to a specific level, the inactivated VG Na+ channels become ________ but not __________. The length of this time defines the:

Answer 7

closed but not inactivated

absolute refractory period

Question 8

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?

Answer 8

absolute refractory period

there aren’t enough VG Na+ channels available to make the depolarization needed for an action potential

Question 9

what causes the hyperpolarization seen at the end of an action potential?

Answer 9

the late opening of VG K+ channels

Question 10

what is the period called when it is possible to elicit an action potential but it requires a larger than normal stimulus?

Answer 10

relative refractory period

Question 11

Guillan-Barre is a loss of myelination in the _________ nervous system

Answer 11

peripheral

Question 12

what two things define this relative refractory period?

Answer 12

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

Question 13

during action potential propagation, the flow of current between two action potentials is ________

Answer 13

electrotonic

Question 14

why do we not get an action potential in the part of the axon where it originally came from?

Answer 14

refractory period of VG Na+ channels

Question 15

what begins repolarization of the membrane potential during an action potential?

Answer 15

inactivation of VG Na+ channels

Question 16

multiple sclerosis is a loss of myelination in the ______. Is it reversible?

Answer 16

CNS

no