24 Questions
Which of the following is NOT true about the heart?
The right heart pumps blood through the systemic circulation
What is the main function of the ventricles in the heart?
To supply the main pumping force
What is the purpose of the pericardium?
To protect the heart
Which of the following is true about cardiac muscle fibers?
They exhibit automatic rhythmical electrical discharge
What causes the twisting motion of the left ventricle during systole?
Contraction of the cardiac muscle fibers
What is the function of the intercalated discs in cardiac muscle fibers?
To allow rapid diffusion of ions
How are the atria and ventricles of the heart connected?
Through fibrous tissue
Which phase of the cardiac action potential is characterized by the closure of calcium ion channels and increased potassium ion permeability?
Phase 3
What is the resting membrane potential of a cardiac cell?
-80 to -60 millivolts
What is the velocity of signal conduction in cardiac muscle fibers?
0.3 to 0.5 m/sec
What is the normal refractory period of the ventricles?
0.25 to 0.30 second
What is the function of the A-V valve?
To open during diastole
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
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
What is the total duration of the cardiac cycle if the heart rate is 72 beats/min?
0.4 of the entire cardiac cycle
What is the function of the atria in the heart?
To increase the ventricular pumping effectiveness by 20%
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.
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.
What is the main factor determining the duration of contraction in cardiac muscle?
The duration of the action potential.
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.
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.
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.
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.
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.
Quiz: Understanding the Cardiac Conduction System Test your knowledge of the cardiac conduction system with this quiz. Learn about the location and function of the node in the right atrium, the pathway of the action potential, and the delay in transmission from the atria to the ventricles.
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