Cardiac Conduction System Quiz

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Which of the following is NOT true about the heart?

The heart is surrounded by a two-layer sac called the pericardium

The atrium is a weak primer pump for the ventricle

The right heart pumps blood through the systemic circulation (correct)

The heart is composed of three major types of cardiac muscle

What is the main function of the ventricles in the heart?

To move blood into the atrium

To protect the heart

To supply the main pumping force (correct)

To pump blood through the lungs

What is the purpose of the pericardium?

To hold the heart in place

To transmit action potentials

To protect the heart (correct)

To contract in the same way as skeletal muscle

Which of the following is true about cardiac muscle fibers?

They exhibit automatic rhythmical electrical discharge Signup and view all the answers

What causes the twisting motion of the left ventricle during systole?

Contraction of the cardiac muscle fibers Signup and view all the answers

What is the function of the intercalated discs in cardiac muscle fibers?

To allow rapid diffusion of ions Signup and view all the answers

How are the atria and ventricles of the heart connected?

Through fibrous tissue Signup and view all the answers

Which phase of the cardiac action potential is characterized by the closure of calcium ion channels and increased potassium ion permeability?

Phase 3 Signup and view all the answers

What is the resting membrane potential of a cardiac cell?

-80 to -60 millivolts Signup and view all the answers

What is the velocity of signal conduction in cardiac muscle fibers?

0.3 to 0.5 m/sec Signup and view all the answers

What is the normal refractory period of the ventricles?

0.25 to 0.30 second Signup and view all the answers

What is the function of the A-V valve?

To open during diastole Signup and view all the answers

Which chamber of the heart is located in the superior lateral wall of the right atrium near the opening of the superior vena cava?

Right atrium Signup and view all the answers

What is the purpose of the delay in the passage of the cardiac impulse from the atria into the ventricles?

To allow the atria to contract before the ventricles Signup and view all the answers

What is the total duration of the cardiac cycle if the heart rate is 72 beats/min?

0.4 of the entire cardiac cycle Signup and view all the answers

What is the function of the atria in the heart?

To increase the ventricular pumping effectiveness by 20% Signup and view all the answers

Which of the following is true about the strength of cardiac muscle contraction compared to skeletal muscle contraction?

The strength of cardiac muscle contraction depends on the concentration of calcium ions in the extracellular fluids. Signup and view all the answers

What is the function of the calcium–adenosine triphosphatase (ATPase) pump in cardiac muscle?

It removes calcium ions from the sarcoplasm and pumps them back into the sarcoplasmic reticulum. Signup and view all the answers

What is the main factor determining the duration of contraction in cardiac muscle?

The duration of the action potential. Signup and view all the answers

Why would a heart placed in a calcium-free solution stop beating?

The calcium ions in the sarcoplasmic reticulum would not be released into the sarcoplasm. Signup and view all the answers

Which of the following is a major difference between the action potential in cardiac muscle and skeletal muscle?

The action potential in cardiac muscle is caused by the opening of fast sodium channels and slow calcium channels, while the action potential in skeletal muscle is caused by the opening of fast sodium channels only. Signup and view all the answers

Which of the following best explains why ventricular contraction lasts longer in cardiac muscle compared to skeletal muscle?

The presence of a plateau in the action potential in cardiac muscle, which is absent in skeletal muscle. Signup and view all the answers

Which of the following best explains the cause of the plateau phase in the action potential in cardiac muscle?

The influx of calcium and sodium ions through slow calcium channels, which maintain depolarization. Signup and view all the answers

Which of the following is a major functional difference between cardiac muscle and skeletal muscle that contributes to the prolonged action potential and plateau in cardiac muscle?

The decreased potassium permeability in cardiac muscle, which does not occur in skeletal muscle. Signup and view all the answers