Unformatted text preview: Go to the next screen: At the peak, the sodium
inactivation gates are closed and potassium gates
have begun to open. The potassium gate is also
voltage dependent. When the membrane reaches the
polarization peak this gate opens to allow potassium
to exit the cell. This gate is slower than the sodium
activation gate and the sodium inactivation gate.
Potassium ﬂows out of the cell, repolarizing it (“unto '3 lmlarlllﬂon G0 to the next screen: Potassium gates are
slow to close and while they are closing there occurs
an after-hypelpolarization (called undershoot here).
Not that the sodium gates are both closed. Now the
inactivation gate will begin to open ”Assn-n :hnnnel doses ' O _ .
[mom “ Undershoot
m“"""" “W*“mm Go to the next screen: Now everything is back to resting membrane state. You can rewind the animation
ifyou wish. Otherwise click the Return Button inn-alum] i 7 7 7 7 7 7 3.7-."7
7a.“... Go to the next screen: This graph shows the
ﬂow of sodium and potassium curves in relationship
._.,...... to the action potential. The rapid depolarization of
u...— meow . . . . .
an,“ ,. phase 1 IS caused by a rapid sodium permeability
”- E S increase that enables sodium to move into the cell.
W l '- 2 The repolarization of phase 2 is caused by a slower
:1,“ an increase in potassium permeability, enabling greater
! as n E ”was. movement of potassium out of the cell compared with
,,, ”- resting conditions. The continuing movement of
A 9 ” M potassium out of the cell causes the after-
LEE; ’5':- *5: ms.» “We hyperpolarization of phase 3. ...
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- Spring '07