Cardiac Action Potentials Quiz

What is a key difference between pacemaker and non-pacemaker action potentials?

• Non-pacemaker cells require external stimuli.

• Pacemaker cells have a resting potential.

• Non-pacemaker cells have automaticity.

• Pacemaker cells require external stimuli.

Why do ventricular myocytes have a lower resting membrane potential compared to skeletal muscle?

• To prevent arrhythmias by requiring a stronger stimulus.

• To enhance potassium permeability.

• To allow easier depolarization.

• To increase automaticity.

What primarily drives the depolarization phase in non-pacemaker cells?

• Slow sodium channels

• Fast sodium channels

• L-type calcium channels

• Potassium channels

Which type of sodium current is associated with automaticity in pacemaker cells?

• Delayed rectifier current

• Fast sodium current

• Slow sodium current

• L-type calcium current

During the plateau phase, which channels are primarily responsible for balancing the membrane potential?

• Delayed rectifier and fast sodium channels

• Slow sodium and calcium channels

• L-type calcium and potassium channels

• Fast sodium and potassium channels

What is the main role of the plateau phase in cardiac action potentials?

• To enhance automaticity

• To sustain ventricular contraction

• To prevent repolarization

• To initiate depolarization

What happens to L-type calcium channels during the late repolarization phase?

• They become activated.

• They remain open.

• They become inactivated.

• They increase sodium permeability.

What is the significance of the absolute refractory period in cardiac action potentials?

• It increases calcium influx.

• It enhances automaticity.

• It prevents new action potentials from starting.

• It allows for immediate reactivation.

How is the QT interval on an EKG related to cardiac action potentials?

• It shows only the repolarization phase.

• It encompasses the entire action potential duration.

• It indicates the depolarization phase only.

• It represents the resting potential.

Which phase of the cardiac action potential is represented by the T wave on an EKG?

• Plateau phase

• Late repolarization phase

• Early repolarization phase

• Depolarization phase