Chapt 17, pt 2 - Cardiac Muscle & Electrical Conduction

What type of muscle tissue makes up the heart?

Cardiac muscle tissue.

How do cardiac muscle cells differ from skeletal muscle cells?

They are branched, usually contain one nucleus, and are connected by intercalated discs.

What structures connect cardiac muscle cells?

Intercalated discs.

What structures within intercalated discs allow electrical signals to spread rapidly?

Gap junctions.

What structures within intercalated discs hold cells together during contraction?

Desmosomes.

What are the two main types of cardiac cells?

Pacemaker cells and contractile cells.

What is the function of pacemaker cells?

They generate spontaneous electrical impulses that initiate heartbeats.

What is the function of contractile cells?

They generate the force needed to pump blood

What structure initiates the heartbeat?

The sinoatrial node.

Where is the sinoatrial node located?

In the right atrium near the superior vena cava.

Why is the SA node called the pacemaker?

Because it sets the normal heart rhythm.

What structure receives the impulse after the SA node?

The atrioventricular node.

Where is the AV node located?

At the lower part of the right atrium near the interatrial septum.

Why does the AV node delay the impulse?

To allow atrial contraction before ventricular contraction.

What structure carries impulses from the atria to the ventricles?

The atrioventricular bundle.

What are the right and left bundle branches?

Conduction pathways in the interventricular septum.

What fibers distribute impulses through ventricular muscle?

Purkinje fibers

What is an electrocardiogram?

A recording of the electrical activity of the heart.

What does the P wave represent?

Atrial depolarization.

What does the QRS complex represent?

Ventricular depolarization.

Why is atrial repolarization not seen on ECG?

It occurs at the same time as ventricular depolarization and is masked by the QRS complex.

What does the T wave represent?

Ventricular repolarization