Lecture 3

Question 1

The probability of the channel being
open is (equal/different) at each value of
membrane voltage

Answer 1

different

Question 2

When there is low membrane potential, VG K+ channels are…

-closed/deactivated
-open/activated

Answer 2

closed/deactivated

Question 3

When there is high membrane potential, VG K+ channels are…

-closed/deactivated
-open/activated

Answer 3

-open/activated

Question 4

If activation and inactivation gates are open, VG Na+ channel is….

-open/activated
-inactivated
-closed/deactivated

Answer 4

-open/activated

Question 5

If activation gate is open but inactivation gate is blocking the channel, VG Na+ channel is….

-open/activated
-inactivated
-closed/deactivated

Answer 5

-inactivated

Question 6

If activation and inactivation gates are blocking the channel, VG Na+ channel is….

-open/activated
-inactivated
-closed/deactivated

Answer 6

-inactivated

Question 7

If activation gate is blocking the channel but the inactivation gate is open, VG Na+ channel is….

-open/activated
-inactivated
-closed/deactivated

Answer 7

-closed/deactivated

Question 8

VG Na+ channels have

-activation gates
-inactivation gates
-both
-none

Answer 8

both activation and inactivation gates

Question 9

VG K+ channels have

-activation gates
-inactivation gates
-both
-none

Answer 9

activation gates

Question 10

If the activation gate is open, VG Na+ and K+ channels are

-depolarized potential
-rest/hyperpolarized potential

Answer 10

-depolarized potential

Question 11

If the activation gate is blocking the channels, VG Na+ and K+ channels are

-depolarized potential
-rest/hyperpolarized potential

Answer 11

-rest/hyperpolarized potential

Question 12

Hyperpolarization is due to an (efflux/influx) of (K+/Na+), making the outside more positive.

Answer 12

Efflux of K+

Question 13

Depolarization is due to an (efflux/influx) of (K+/Na+).

Answer 13

Influx of Na+

Question 14

If [Na+]out is reduced, the overshoot of the action potential will (increase/decrease).

Answer 14

decrease

Question 15

If [K+]out is increased, the undershoot of the action potential will (increase/decrease).

Answer 15

increase

Question 16

The THRESHOLD for the AP firing is the membrane
potential:

Answer 16

– at which the Na+ influx…
– overcomes the K + efflux…
– resulting in an action potential (or more than one).

Question 17

At the resting potential:

gK < gNa
gK = gNa
gK > gNa

Answer 17

gK > gNa – when only leak channels are open – more K leak channels

Question 18

When the AP is rising:

gK < gNa
gK = gNa
gK > gNa

Answer 18

gK < gNa – VG Na channels open

Question 19

When the Ap is falling:

gK < gNa
gK = gNa
gK > gNa

Answer 19

gK > gNa - VG Na channels are inactivated + VG K channels open

Question 20

At resting potential after an AP:

gK < gNa
gK = gNa
gK > gNa

Answer 20

gK > gNa - VG Na+ channels are inactivated/closed and VG K channels closed – only leak channels open

Question 21

What two types of refractory periods are there?

Answer 21

Absolute refractory period
Relative refractory period

Question 22

What is the Absolute refractory period?

Answer 22

The period of time after an AP occurs where it is
impossible to trigger a new AP.
–Mostly due to the post-AP inactivation of most of the VG Na+
channels in the cell

Question 23

What is the Relative refractory period?

Answer 23

The period of time after an AP occurs where it is
necessary to provide a stronger input in order to trigger an
AP.
– Due mostly to the fact that VG K+ channels are still open,
increasing K+ conductance. The residual inactivation of a few VG Na+ channels also contributes

Question 24

What comes first after an AP is fired? ARP or RRP?

Answer 24

ARP

Question 25

The initial rise and final amplitude of an AP
are ?? dependent while the falling phase and
undershoot depend on ??

Answer 25

initial rise = Na+ dep
falling/undershoot = K+ dep

Question 26

The THRESHOLD for the AP firing is the membrane
potential:

Answer 26

– at which the Na+ influx…
– overcomes the K + efflux…
– resulting in an action potential (or more than one)

Question 27

When a positive ion or negative ion enters a cell, it is (depolarized/hyperpolarized) which (increases/decreases) the volt.

Answer 27

hyperpolarized - increases

Question 28

A positive/outward current results in a (increase/decrease) in voltage.

Answer 28

decrease

Question 29

What current is blocked when TEA is used to isolate the membrane current?

Answer 29

K+ current

Question 30

What current is blocked when TTX is used to isolate the membrane current?

Answer 30

Na+ current

Question 31

The early current is mediated by ___________ and the late current is mediated by ________ channels

Answer 31

VG Na+ channels; VG K+ channels

Question 32

What does membrane conductance (Gion) mean?

Answer 32

the ability of charged ions to move across a cell membrane through protein pores. IT is a measure of the electrical flow from one pt to another

Question 33

The activation of Na+ and K+ voltage gated
channels is dep on:

voltage
time
both
neither

Answer 33

voltage and time dependent

Question 34

Na+ and K+ voltage gated
channels open faster at more (depolarized/hyperpolarized) potentials.

Answer 34

depolarized

Question 35

What has faster kinetics of activation? VG Na+ channels or VG K+ channels

Answer 35

VG Na+

Question 36

The depolarization of AP including the increase of Na+ current and opening of Na+ channels is a (slow/fast) (negative/positive) cycle.

Answer 36

fast positive

Question 37

The hyperpolarization of AP including the increase in K+ current and opening of K+ channels is a (slow/fast) (negative/positive) cycle.

Answer 37

slow negative