Heart Electrical Activity and Function

Dr. Ketchum explains the spread of action potentials in the heart, starting with pacemaker cells in the SA node. The action potentials travel through the atria via interatrial and internodal pathways, reaching the AV node where a delay allows for atrial contraction. This delay ensures the ventricles are filled before they contract. The action potentials then move through the bundle of His and Purkinje fibers, leading to ventricular contraction. The heart then rests briefly before the cycle repeats.

What is the primary function of pacemaker cells in the heart?

• To contract the heart muscles

• To set the heart rate

• To supply blood to the heart

• To repair damaged heart tissue

Which part of the heart is responsible for starting the entire process of action potential generation?

• Purkinje fibers

• SA node

• Bundle of His

• AV node

Which pathway allows the action potential to spread to the left atrium?

• Purkinje fibers

• Internodal pathway

• Interatrial pathway

• Bundle of His

What is the purpose of the AV nodal delay?

• To synchronize the contraction of the atria and ventricles

• To prevent action potentials from reaching the ventricles

• To allow the ventricles to fill with blood

• To speed up the heart rate

What percentage of the ventricles is filled with blood before the atria contract?

• 100%

• 80%

• 60%

• 50%

Where do action potentials travel after leaving the AV node?

• Directly to the ventricles

• To the SA node

• Through the interatrial pathway

• Down the bundle of His

What happens when action potentials reach the apex of the heart?

• The action potentials dissipate

• The heart stops

• The ventricles contract

• The atria contract

What is the role of the Purkinje fibers in the heart?

• To contract the atria

• To delay the action potentials

• To spread action potentials up the walls of the ventricles

• To initiate action potentials

What is the sequence of events in the heart's electrical and mechanical activity?

• Mechanical event followed by electrical event

• Electrical event followed by mechanical event

• Both events occur simultaneously

• There is no specific sequence

What happens to the heart after the ventricles contract?

• It contracts again

• It immediately starts a new cycle

• It enters a resting state

• It stops functioning