Cardiac Muscle Physiology and Conducting System

Flashcards about Cardiac Muscle Physiology and Conducting System

How does cardiac muscle differ from skeletal muscle in terms of action potential generation?

Cardiac muscle spontaneously depolarizes and does not need an action potential from the nervous system to open Na+ gates.

What is the conducting system of the heart?

A system of specialized cardiac muscle cells that initiates and distributes electrical impulses to stimulate contraction.

What is the property of cardiac muscle tissue that allows it to contract automatically?

Automaticity or Autorhythmicity

What are the main structures of the conducting system?

Sinoatrial (SA) node, Atrioventricular (AV) node, Conducting cells

What is prepotential (pacemaker potential)?

The resting potential of conducting cells that gradually depolarizes toward threshold.

How many action potentials does the SA node generate per minute?

80–100 action potentials per minute.

How many action potentials does the AV node generate per minute?

40–60 action potentials per minute.

What is the correct order of the steps in the conduction system?

SA Node -> Internodal pathway -> AV Node -> AV Bundle -> Bundle Branches -> Purkinje Fibers

What is the role of the AV bundle in the conduction system?

Carries impulse to left and right bundle branches which conduct to Purkinje fibers and to the moderator band, which conducts to papillary muscles.

How does the cardiac cycle begin?

Begins with action potential at SA node, transmitted through conducting system and produces action potentials in cardiac muscle cells (contractile cells).

What are the four major electrical events recorded by an electrocardiogram (ECG/EKG)?

Atria depolarize, Atria repolarize, Ventricles depolarize, Ventricles repolarize.

What does the P wave on an EKG/ECG represent?

Atria depolarize.

What does the P–R interval on an EKG/ECG represent?

From start of atrial depolarization to start of QRS complex.

What is bradycardia?

Abnormally slow heart rate.

What is tachycardia?

Abnormally fast heart rate.

What is an ectopic pacemaker?

Abnormal cells that generate a high rate of action potentials, bypass the conducting system, and disrupt ventricular contractions.