Action Potential

An action potential is how ______________________

messages travel down the axon of neurons

Action potential is a ___________ charge created by the ___________________

positive; ratio of Na+ to K+ ions in the cell

Step 1: ___________

Resting State

Resting State Picture

Resting State: The activation gates on the Na+ and K+ channels are _______

closed

Resting State: The charge of the cell membrane is ____________. This is called the Resting State.

Negative (-70 mv)

Resting State: Na+ is on the _________ of the cell

outside

Resting State: K+ is on the _______ of the cell.

inside

Step 2: ________

Depolarization

Depolarization Picture

Depolarization: A stimulus opens __________________________________________

the activation goes on some Na+ channels

Depolarization: The K+ channels still __________ and K+ cannot __________

closed; leave

Depolarization: Na+ goes in and ___________________

depolarizes the membrane

Depolarization:

• Depolarization

makes the charge more positive

Depolarization: If depolarization reaches the threshold _______________, it triggers an _________________. This occurs at about _________.

(if enough Na+ goes in); action potential; -55 mv

Step 3: _____________________________

Rising phase of action potential

Rising phase of action potential Picture

Rising phase of action potential: Depolarization opens the _____________________________________

activation gates on most Na+ channels

Rising phase of action potential: K+ channels remain ________

closed

Rising phase of action potential: Na+ influx makes the inside of the cell _____________ charged compared to the outside

positively

Rising phase of action potential: This is the peak of action potential and it reaches _______

+30 mv

Step 4: __________________________________

Falling Phase of Action Potential

Falling Phase of Action Potential Picture

Falling Phase of Action Potential: The inactivation goes on most Na+ channels __________, so Na+ can’t go in anymore

close

Falling Phase of Action Potential: Activation goes on most K+ channels ____, and K+ can leave the inside of the cell, making the inside _______________________ again.

open; negatively charged

Step 5: ______________

Overshoot

Overshoot Picture

Overshoot: Both gates of the Na+ channels _________

close

Overshoot: Activation gates of some K+ channels stay ________

open

Overshoot: The charge inside the cell starts to get too __________ and “overshoots” the resting potential

negative

K+ gates start to close and the membrane _______________________________

returns to resting state of -70 mv