Action Potential

Question 1

Summation

Answer 1

A sufficient number of local potentials spaced closely together are summed together to cause a significant change in membrane potential (excitatory or inhibitory)

Question 2

Summation - Temporal

Answer 2

-A series of local potentials occurring at the same place close together in time

Question 3

Summation - Spatial

Answer 3

Local potentials occurring at the same time in close proximity to each other (close together in space) on the same neuron

Question 4

What is action potential?

Answer 4

• If there is enough summation to achieve =15mV of change in membrane potential, fast voltage-gated Na+ channels open
• Na+ ions rush into the neuron
• Na+ rushing into the neuron changes the membrane potential to +35mV

Question 5

Action potential - membrane at the end of the depolarization phase?

Answer 5

Is fully depolarized

-Just before reaching peak, the fast voltage-gated Na+ channels begin to close and become inactive (can not open)

Question 6

Action potential - Repolarization

Answer 6

• Slow voltage-gated K+ channels open
• K+ flows out of the cell
• Membrane potential becomes more negative
• K+ channels begin to close in late phase of repolarization

Question 7

Action potential - Hyperpolarization

Answer 7

Membrane potential goes to slightly below resting level
-K+ channels fully close by peak hyperpolarization. Diffusion of ions through leak channels and continued action of the Na+-K+ pump restores the resting membrane potential

Question 8

Action potential - Summary 1

Answer 8

Action potential is all or none

• You can’t have a partial AP
• If you reach the threshold, an AP will be generated
• If you do not reach threshold, no AP will be generated

Question 9

Action potential - Summary 2

Answer 9

Summination of local potentials results in reaching threshold and the generation of an action potential.

• Rapid and large depolarization as the voltage-gated Na+ channels open and Na+ enters the cell (influx)
• Voltage-gated Na+ channels close and become inactive

Question 10

Action potential - Summary 3

Answer 10

Slower to open voltage-gated K+ channels open and K+ leaves the cell (efflux) resulting in repolarization

• Continued outward flow of K+ leads to hyperpolarization
• K+ channels fully close. Diffusion of ions through leak channels and continued action of the Na+-K+ pump restores the resting membrane potential.

Question 11

Action potential Refractory period

Answer 11

The interval of time when the cell cannot generate an action potential or requires a stronger than normal stimulus to do so
-Helps to prevent the backflow of an action potential

Question 12

Absolute refractory period

Answer 12

Membrane is unresponsive to stimuli

• A second action potential cannot be generated
• Begins at threshold and ends sometime during repolarization

Question 13

Relative refractory peiord

Answer 13

A stronger than normal stimulus is required to open the voltage-gated Na+ channels and generated a second action potential

• Starts at the end of an absolute period when Na+ gates start to become active again and some K+ still leaving
• Ends once back to RMP after completion of hyperpolarization phase