Week 5 & 6: Cardiovascular System (inc. practical)

At rest, the heart rate is most affected by which of the following? 1.Circulating epinephrine

2.Parasympathetic (vagal) nervous innervation

3.Sympathetic nervous system

Parasympathetic (vagal) nervous innervation. At rest, the vagal effect predominates (vagal tone), and the heart beats more slowly than it would in the absence of any autonomic activity

During moderate exercise, the heart rate is most affected by which of the following?

1.Decreased levels of circulating epinephrine

2.Increased parasympathetic (vagal) nervous innervation

3.Increased sympathetic nervous innervation

Increased sympathetic nervous innervation. During exercise, vagal activity diminishes and sympathetic activity increases

The RR interval is the time elapsed between two successive R-waves of the QRS signal. How did the RR interval and the heart rate change during exercise?

1.RR interval decreases, heart rate decreases

2.RR interval decreases, heart rate increases

3.RR interval increases, heart rate decreases

4.RR interval increases, heart rate increases

RR interval decreases, heart rate increases

Which of the following is altered the most in conditions where heart rate is increased?

1.PR interval

2.QRS interval

3.T wave duration

4.TP segment

TP segment. Tg segment is altered most when HR is increased. A decreased TP segment reflects a decreased ventricular filling time, which occurs when the HR is increased.

Which component of the electrical conduction system is the "pacemaker"?

1.AV node

2.Bundle of His

3.Purkinje fibers

4.SA node

SA node. The SA node generates cardiac APs at a greater frequency than other cardiac muscle cells

What does an ECG measure?

1.An individual cardiac action potential.

2.Mechanical events in the heart.

3.The collective electrical activity of the heart.

4.The movement of the cardiac muscles.

The collective electrical activity of the heart.

Cause of an atrial flutter?

Type of abnormal heart rhythm, when the signal from the SA node travels rapidly in a continuous loop around the atria

How would these periods change during exercise?

P wave
PR interval
QRS complex
T wave
QT interval

During exercise, an increase in HR would correspond to a shorter cardiac cycle. the RR interval (time between 2 successive R waves) decreases. Most reduction happens at the TP interval (time between the T wave of 1 beat and the P wave of the next beat)

What are each of the lead's of the Einthoven's triangle?

Lead I: LA–RA
Lead II: LF–RA
Lead III: LF–LA

Which of the Einthoven's triangle lead is most closely aligned with the direction of ventricular depolarisation?

Lead II has the largest R wave, and also shows the P and T waves as positive.

Which region of the heart generates electrical activity the fastest?

SA node

Why is it important that there is slower conduction of the electrical signal through the AV node (and its extension, the bundle of His)?

1.The delay allows the atria to contract completely before ventricular contraction begins.

2.The delay allows the left atrium to contract completely before the right atrium starts to contract.

3.The delay gives time for the blood to travel from the ventricles to the atria.

The delay allows the atria to contract completely before ventricular contraction begins.

When a wave of depolarisation travels toward a positive electrode, how is this represented on an ECG tracing?

1.Downward from the baseline

2.No change from the baseline (horizontal)

3.Upward from the baseline

3.Upward from the baseline

When a wave of repolarization travels toward a negative electrode, how is this represented on an ECG tracing?

1.Downward from the baseline

2.No change from the baseline (horizontal)

3.Upward from the baseline

Downward from the baseline