Phases of the action potential

Question 1

What are the 7 parts of the phases of the action potential?

Answer 1

depolarization 
repolarization 
hyperpolarization 
threshold 
all-or-none phenomenon 
absolute refractory period 
relative refractory period

Question 2

a stimulus (at or above threshold) causes the activation gate of the voltage-gated Na+ channels to open, Na+ flows in due to its electrochemical gradient and the cell becomes more positive (less negative)

Answer 2

depolarization

Question 3

What does depolarization establish?

Answer 3

a positive feedback loop

Question 4

sodium flowing into the cell causes more voltage-gated Na+ channels to open

Answer 4

positive feedback loop

Question 5

In depolarization what causes the activation gate of the voltage-gated Na+ channels to open?

Answer 5

a stimulus at or above threshold

Question 6

In depolarization why does Na+ flow into the cell?

Answer 6

due to the electrochemical gradient

Question 7

What happens to the cell when Na+ flows in due to its electrochemical gradient in depolarization?

Answer 7

the cell becomes more positive (less negative)

Question 8

Depolarization establishes a positive feedback, which causes?

Answer 8

sodium flwoing into the cell causes more voltage-gated Na+ channels to open

Question 9

In depolarization where is the density of voltage gated Na+ channels the greatest?

Answer 9

on the axon hillock

Question 10

When the voltage gets clost to +30mV, the Na+ inactivation gates start to close and voltage gated K+ channels open, K+ moves out of the cell with its electrochemical gradient

Answer 10

repolarization

Question 11

In repolarization when do the Na+ inactivation gates strat to close and voltage-gated K+ channels open?

Answer 11

when the voltage gets close to +30mV

Question 12

Where does K+ move with repolarization?

Answer 12

K+ moves out of the cell with its electrochemical gradient

Question 13

The K+ channels stay open for a short time resulting in the cell becoming slightly more negative than the resulting membrane potential.

Answer 13

hyperpolarization

Question 14

In hyperpolaization what do the K+ channels staying open for a short time result in?

Answer 14

the cell becomes more negative than the resting membrane potential

Question 15

the minimum change in voltage that will result in an action potential usually a depolaization of 15 to 30 mV

Answer 15

threshold

Question 16

if threshold is met an action potential will occur, smaller stimuli will not generate an action potential

Answer 16

all-or-none phenomenon

Question 17

voltage-gated sodium channels are inactivated due to the closing of the inactivation gate, the neuron can not respond to a stimulus no matter how strong

Answer 17

absolute refractory period

Question 18

During absolute refractory period why are voltage-gated sodium channels inactivated?

Answer 18

due to the closing of the inactivation gate

Question 19

if the stimulus is greater than the previous stimulus (suprathreshold) sodium gates will reopen, this must follow the absolute refractory period.

Answer 19

relative refractory period

Question 20

In relative refractory period why will sodium gates reopen?

Answer 20

if the stimulus is greater than the previous stimulus (suprathreshold)

Question 21

What must relative refractory period follow?

Answer 21

absolute refractory period