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1

The
separation of charges makes each cell a

battery

2

the cells' resting potential is a power source that generates

action potentials

3

are proteins in the cell membrane that confer permeability to ions

Ion channels

4

K+
channels are always open regardless of membrane potential. t/f

True

5

channels that are gated (opened and closed) by the membrane potential

voltage gated ion channels

6

Two types of voltage gated ion channels generate action potentials. Please enumerate

voltage gated
sodium channel and the other is a voltage gated potassium channel.

7

three main
features of the channel (voltage gated sodium channels)

1. central pore that is selectively permeable to Na+ ions;
2. activation gate
3. inactivation gate

8

hat is closed at the resting potential
but is opened by depolarization (when the inside of the cell becomes less negative than rest);

voltage gated Na channel - activation gate

9

Na channel that is open at rest but is closed by
depolarization.

inactivation gate

10

inactivation gate is also referred to as a

“ball and chain"

11

has a structure such that a length of amino acids forms a chain-like structure that is linked to
another group of amino acids that forms a ball-like structure.

inactivation gate

12

when neurons are at
rest, at about -70 mV, what is the status of voltage gated Na channels

activation gate is closed and the inactivation is open.

13

The whole
idea of depolarization is to
(status of voltage gated Na channels )

open the activation gate and close the inactivation gate

14

However,
an important feature of the two gates is that when the axon is depolarized, the opening of the
activation gate is just slightly faster than the

closing of the inactivation gate

15

After the activation gate has been open for about ___, the slower inactivation gate
swings shut, thereby plugging the pore and preventing the further influx of Na+ ions into the cell.

1.0 ms

16

as a selflimiting
gate that allows the pore to be open for only about a 1.0 ms and no longer.

inactivation gate

17

membrane just under the open Na channel will approach this potential

sodium equilibrium potential, ENa,

18

sodium equilibrium potential, ENa, which is about

+55 mV (inside positive).

19

during depolarization, this brief period of less than 1.0 ms (1/1000 of a second); the
membrane potential spikes from a resting value of -70 mV to +55 mV, a net change of

125
mV

20

This spike in the membrane potential, from -70 to +55 mV, is what comprises the ___ of action potential

upstroke

21

is a stereotyped event
that is triggered by depolarization of the membrane

action potential, or spike

22

Typically the first depolarization that starts the entire cycle is due to the influx of positive
charges caused by the release of transmitter at the synapse. But once the spike or action
potential is first initiated at the axon hillock, it is reproduced over and over again at each
point along the axon, because of the presence of what structure

voltage gated sodium channels

23

The rapid re-polarization of the membrane
potential is accomplished by the

opening of voltage-gated potassium channels- efflux of K+ ions.

24

their
purpose is for the rapid efflux of positive charges from the inside of the cell to the outside.

voltage gated potassium channels

25

The reason that positive charges can be carried in by one ion (Na+)
and removed by another ion (K+) is that the opening (or closing) of channels depends ONLY
on the

charge inside the membrane

26

VOLTAGE GATED CHANNELS
OPERATE THOUGH

EQUAL OPPORTUNITY” CHARGES

they care only about charge and
are oblivious to whether the charge was carried by K+, Na +, or Ca++ ions

27

Na+ channels open

upstroke

28

downstroke

Na+ inactivation gates are closing
K channels are opening

29

Only K+ channels are open. membrane is at Ek

undershoot

30

both Na and K are closed

RM