Lecture #22: EKGs & Cardiac Contraction

A collection of key concepts and details related to EKGs and cardiac contraction, useful for exam preparation.

What does an electrocardiogram (ECG or EKG) measure?

It measures the composite of all action potentials generated by pacemaker and contractile cells at a given time.

What is the purpose of Einthoven's Triangle in electrocardiography?

It provides a simple form of measuring the heart's electrical activity using 3 leads.

What are the three major waves seen in an EKG and what do they represent?

P wave represents atrial depolarization, QRS complex represents ventricular depolarization, and T wave represents ventricular repolarization.

What occurs during the P-R interval on an EKG?

It represents the time from the beginning of atrial excitation to the beginning of ventricular excitation.

What is the significance of the S-T segment on an EKG?

It indicates that the entire ventricular myocardium is depolarized.

What are the two primary types of heart valves involved in blood flow?

Atrioventricular (AV) valves and semilunar (SL) valves.

Describe the process of ventricular filling during the cardiac cycle.

It takes place in mid-to-late diastole when AV valves are open and blood passively flows into the ventricles.

What happens during iso-volumetric contraction?

All valves are closed, and no blood is moving as the ventricles begin to contract, raising pressure.

What is end systolic volume (ESV)?

It is the volume of blood remaining in each ventricle after systole.

What triggers the opening of the AV valves during the cardiac cycle?

The AV valves open when atrial pressure exceeds ventricular pressure.