Flashcards in Introduction to the Action Potential Deck (48)
separation of charges makes each cell a
the cells' resting potential is a power source that generates
are proteins in the cell membrane that confer permeability to ions
channels are always open regardless of membrane potential. t/f
channels that are gated (opened and closed) by the membrane potential
voltage gated ion channels
Two types of voltage gated ion channels generate action potentials. Please enumerate
sodium channel and the other is a voltage gated potassium channel.
features of the channel (voltage gated sodium channels)
1. central pore that is selectively permeable to Na+ ions;
2. activation gate
3. inactivation gate
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
Na channel that is open at rest but is closed by
inactivation gate is also referred to as a
“ball and chain"
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.
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.
idea of depolarization is to
(status of voltage gated Na channels )
open the activation gate and close the inactivation gate
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
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.
as a selflimiting
gate that allows the pore to be open for only about a 1.0 ms and no longer.
membrane just under the open Na channel will approach this potential
sodium equilibrium potential, ENa,
sodium equilibrium potential, ENa, which is about
+55 mV (inside positive).
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
This spike in the membrane potential, from -70 to +55 mV, is what comprises the ___ of action potential
is a stereotyped event
that is triggered by depolarization of the membrane
action potential, or spike
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
The rapid re-polarization of the membrane
potential is accomplished by the
opening of voltage-gated potassium channels- efflux of K+ ions.
purpose is for the rapid efflux of positive charges from the inside of the cell to the outside.
voltage gated potassium channels
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
charge inside the membrane
VOLTAGE GATED CHANNELS
EQUAL OPPORTUNITY” CHARGES
they care only about charge and
are oblivious to whether the charge was carried by K+, Na +, or Ca++ ions
Na+ channels open
Na+ inactivation gates are closing
K channels are opening
Only K+ channels are open. membrane is at Ek