Lab Week 3: Monitoring and analyzing electrocardiograms

What are the two types of cardiac muscle cells involved in a single cardiac contraction?

Specialized muscle cells and contractile cells

What is the function of the specialized muscle cells of the conduction system?

They control the heartbeat.

What is the function of the contractile cells in the heart?

They propel the blood.

What does the cardiac conduction system do?

generates and coordinates heartbeat through electrical impulses.

How does cardiac tissue differ from skeletal muscle in terms of contraction?

Cardiac tissue contracts without neural or hormonal stimulation.

What is the property of cardiac tissue that allows it to contract on its own?

automaticity or autorhythmicity

What initiates the conduction pathway in the heart?

The action potential generated by the Sinoatrial (SA) node.

Where is the SA node located?

Near the entrance of the superior vena cava in the posterior wall of the right atrium.

What is the function of the pacemaker cells in the SA node?

They establish the rate at which the heart contracts.

How does the signal from the SA node travel through the heart?

It spreads across the atria to the Atrioventricular (AV) node.

Where is the AV node located?

At the bottom of the interatrial septum next to the right atrioventricular valve.

What happens after the signal reaches the AV node?

The signals leave the AV node through the Atrioventricular (AV) bundle (bundle of His).

What happens after the AV bundle (bundle of His) receives the signal?

It splits into the right and left bundle branches, continuing along the interventricular septum toward the apex.

How does the conduction continue after the bundle branches?

The branches diverge around the ventricles, spreading excitation to the Purkinje fibers.

What is the role of the Purkinje fibers in the conduction pathway?

They distribute the stimulus throughout the myocardium of the ventricles.

What is the normal heartbeat established by the SA node called?

Sinus rhythm.

What is an ectopic focus?

A spontaneous signal created in any area other than the SA node.

What happens if the SA node is damaged?

The AV node may take over control of the heartbeat.

What is nodal rhythm?

A normal but slower heart rate controlled by the AV node.

What is an arrhythmia?

Any abnormal cardiac rhythm.

What causes an arrhythmia?

A blockage or delay in the electrical signals of the cardiac conduction system.

Are all arrhythmias life-threatening?

No, some may not be life-threatening.

What is an electrocardiogram (EKG/ECG)?

A graphical recording of the electrical events occurring within the heart.

How many identifiable deflections are in a typical EKG tracing?

Five (P, Q, R, S, T).

What does the P wave represent?

Depolarization of the atria.

What is the QRS complex?

A complex consisting of Q, R, and S waves representing ventricular depolarization.

Why is atrial repolarization usually not visible on an EKG?

It is masked by the intensity of the QRS complex.

What does the T wave represent?

Repolarization of the ventricles before ventricular diastole.

What are segments and intervals in an EKG?

Segments extend from one wave end to another; intervals include at least one wave and measure specific time periods.

What does the PR interval represent?

The time from the start of atrial depolarization to the start of ventricular depolarization (QRS complex).

Why does the PR interval end at the start of the QRS complex instead of the R peak?

The R peak is difficult to determine in abnormal EKGs.

What does the QT interval represent?

The time required for ventricles to depolarize and repolarize in a single cycle.

What does the PQ segment indicate?

The time for an impulse to spread from the SA node to the AV node.

What does the ST segment represent?

The period when the ventricles are depolarized before repolarization.

Why is an EKG valuable in diagnosing heart conditions?

It records the heart's electrical events, helping identify diseases that affect conduction.

What happens when cardiac muscle cells are damaged or destroyed?

They can no longer conduct electrical impulses.

How does damaged cardiac tissue affect electrical signals?

Signals terminate at the damaged tissue or deviate from normal flow.

How does altered electrical signaling affect the heart?

It changes the way the heart contracts.

How can a cardiologist detect heart muscle damage using an EKG?

By analyzing the waveform and time intervals between electrical events.

Where is the heart's natural pacemaker located?

In the right atrium, known as the sinoatrial (SA) node

What does the SA node do?

It initiates the electrical sequence for heart contraction.

How does the electrical impulse travel through the heart?

From the SA node → atria → AV node → ventricles.

Why are natural conduction pathways important?

They ensure the orderly spread of impulses and coordinated contraction of atria and ventricles.

What do the deflections in an EKG represent?

The electrical activity of the heart, indicating function and health.

How is more information obtained from an EKG?

By placing electrodes in different positions on the chest and extremities.

What does a positive deflection in an EKG tracing indicate?

Electrical activity moving toward the active lead.

Where is the heart's natural pacemaker located?

In the right atrium, sinoatrial (SA) node.

What does the SA node do?

It initiates the electrical sequence for heart contraction.

How does the electrical impulse travel through the heart?

From the SA node → atria → AV node → ventricles.

Why are natural conduction pathways important?

They ensure the orderly spread of impulses and coordinated contraction of atria and ventricles.

What do the deflections in an EKG represent?

The electrical activity of the heart, indicating function and health.

How is more information obtained from an EKG?

By placing electrodes in different positions on the chest and extremities.

What does a positive deflection in an EKG tracing indicate?

Electrical activity moving toward the active lead.

What heart disorders can be detected using an EKG?

Abnormal heart rhythms, injury to muscle tissue, and myocardial infarction (tissue death).

What does the length of an interval in an EKG indicate?

Whether an impulse is following its normal pathway.

What does a long interval in an EKG mean?

The impulse was slowed or took a longer route.

What does a short interval in an EKG mean?

The impulse followed a shorter route.

What does an absent complex in an EKG indicate?

The impulse did not arise normally or was blocked.

What does an absent P wave indicate?

Lack of normal atrial depolarization.

What does an absent QRS complex after a normal P wave suggest?

The electrical impulse was blocked before reaching the ventricles.

What causes abnormally shaped complexes in an EKG?

Abnormal impulse spread due to tissue injury or death (e.g., myocardial infarction).

Besides heart disorders, what else can alter electrical patterns in an EKG?

Metabolic abnormalities and certain medications.