10.17 Action Potential Flashcards

1
Q

can action potentials be summed?

A

no

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2
Q

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

A

independent

dependent

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3
Q

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

A

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

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4
Q

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

A

axon diameter

myelination

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5
Q

graded potentials have what three properties?

A

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

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6
Q

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

A

larger

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7
Q

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

A

closed but not inactivated

absolute refractory period

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8
Q

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?

A

absolute refractory period

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

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9
Q

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

A

the late opening of VG K+ channels

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10
Q

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

A

relative refractory period

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11
Q

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

A

peripheral

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12
Q

what two things define this relative refractory period?

A

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

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13
Q

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

A

electrotonic

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14
Q

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

A

refractory period of VG Na+ channels

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15
Q

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

A

inactivation of VG Na+ channels

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16
Q

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

A

CNS

no