012 The Absolute and Relative Refractory Periods

In this video, Leslie Samuel explains the concepts of absolute and relative refractory periods in neurons. The video begins with an overview of voltage-gated sodium channels, which have three states: closed, open, and inactive. The absolute refractory period occurs when these channels are open or inactive, preventing another action potential. The relative refractory period follows, requiring a stronger stimulus to initiate another action potential as sodium channels reset. The video concludes with a summary of these concepts.

What are the three states of voltage gated sodium channels?

• Closed, Active, and Inactive

• Open, Active, and Inactive

• Open, Closed, and Active

• Open, Closed, and Inactive

What happens when a stimulus causes the membrane potential to exceed the threshold?

• The membrane potential decreases

• An action potential is generated

• The neuron depolarizes without an action potential

• The neuron becomes inactive

During the absolute refractory period, why can't another action potential be initiated?

• The sodium channels are closed

• The sodium channels are either open or inactive

• The potassium channels are open

• The membrane potential is too low

What is required to initiate another action potential during the relative refractory period?

• A weaker stimulus

• A stronger stimulus

• A stimulus of the same strength

• No stimulus

What occurs during the repolarization phase?

• The membrane potential becomes more positive

• Potassium ions rush out of the cell

• The sodium channels become inactive

• Sodium ions rush into the cell

What marks the end of the relative refractory period?

• All potassium channels are closed

• All sodium channels are open

• All sodium channels are inactive

• All sodium channels are reset to the closed state

What is the role of the inactivation gate in sodium channels?

• To open the channel

• To keep the channel open indefinitely

• To close the channel after a short period

• To prevent potassium ions from entering