Block 3 Cardiophysiology Part 1
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- 1.Which of the following normally has the most prominent prepotential?
- A.
Sinoatrial node
- B.
Atrial muscle cells
- C.
Bundle of His
- D.
Purkinje fibers
- E.
Ventricular muscle cells
- 2.Currents caused by opening of which of the following channels contribute to the repolarization phase of the action potential of ventricular muscle fibers?
- A.
Na+ channels
- B.
Cl- channels
- C.
Ca2+ channels
- D.
K+ channels
- E.
HCO3- channels
- 3.In the sinoatrial (SA) node, phase 4 depolarization (pacemaker potential) is attributable to
- A.
An increase in K+ conductance
- B.
An increase in Na+ conductance
- C.
A decrease in C1- conductance
- D.
A decrease in Ca2+ conductance
- E.
Simultaneous increases in K+ and C1- conductances
- 4.During which phase of the ventricular action potential is the membrane potential closest to the K+ equilibrium potential?
- A.
Phase 0
- B.
Phase 1
- C.
Phase 2
- D.
Phase 3
- E.
Phase 4
- 5.During which phase of the ventricular action potential is the conductance to Ca2+ highest?
- A.
Phase 0
- B.
Phase 1
- C.
Phase 2
- D.
Phase 3
- E.
Phase 4
- 6.Which phase of the ventricular action potential coincides with diastole?
- A.
Phase 0
- B.
Phase 1
- C.
Phase 2
- D.
Phase 3
- E.
Phase 4
- 7.During which phase of the cardiac cycle does the mitral valve open?
- A.
Atrial systole
- B.
Isovolumetric ventricular contraction
- C.
Rapid ventricular ejection
- D.
Reduced ventricular ejection
- E.
Isovolumetric ventricular relaxation
- 8.The ventricles are completely depolarized during which isoelectric portion of the electrocardiogram (ECG)?
- A.
PR interval
- B.
QRS complex
- C.
QT interval
- D.
ST segment
- E.
T wave
- 9.Cardiac output of the right side of the heart is what percentage of the cardiac output of the left side of the heart?
- A.
25%
- B.
50%
- C.
75%
- D.
100%
- E.
125%
- 10.If the ejection fraction increases, there will be a decrease in
- A.
Cardiac output
- B.
End-diastolic volume
- C.
End-systolic volume
- D.
Heart rate
- E.
Pulse pressure
- 11.A ventricle has a volume of 100ml and an ejection fraction of 75%: If the heart rate is 70 beats/min, then cardiac output of this ventricle is closest to
- A.
3.45 L/min
- B.
4.55 L/min
- C.
5.25 L/min
- D.
8.00 L/min
- E.
9.85 L/min
- 12.The second heart sound is caused by
- A.
Closure of the aortic and pulmonary valves
- B.
Vibrations in the ventricular wall during systole
- C.
Ventricular filling
- D.
Closure of the mitral and tricuspid valves
- E.
Retrograde flow in the vena cava
- 13.The fourth heart sound is caused by
- A.
Closure of the aortic and pulmonary valves
- B.
Vibrations in the ventricular wall during systole
- C.
Ventricular filling
- D.
Closure of the mitral and tricuspid valves
- E.
Retrograde flow in the vena cava
- 14.Inspiration "splits" the second heart sound because
- A.
The aortic valve closes before the pulmonic valve
- B.
The pulmonic valve closes before the aortic valve
- C.
The mitral valve closes before the tricuspid valve
- D.
The tricuspid valve closes before the mitral valve
- E.
Filling of the ventricles has fast and slow components
- 15.During exercise, a man consumes 1.8 L of oxygen per minute. His arterial O2 content is 190 ml/L, and the O2 content of his mixed venous blood is 134 ml/L. His cardiac output is approximately
- A.
3.2 L/min
- B.
16 L/min
- C.
32 L/min
- D.
54 L/min
- E.
160 ml/min
- 16.The work performed by the left ventricle is substantially greater than that performed by the right ventricle, because in the left ventricle
- A.
The contraction is slower
- B.
The wall is thicker
- C.
The stroke volume is greater
- D.
The preload is greater
- E.
The afterload is greater
- 17.When a person moves from a supine position to a standing position, which of the following compensatory changes occurs?
- A.
Decreased heart rate
- B.
Increased contractility
- C.
Decreased total peripheral resistance (TPR)
- D.
Decreased cardiac output
- E.
Increased PR intervals
- 18.During exercise, total peripheral resistance (TPR) decreases because of the effect of
- A.
The sympathetic nervous system on splanchnic arterioles
- B.
The parasympathetic nervous system on skeletal muscle arterioles
- C.
Local metabolites on skeletal muscle arterioles
- D.
Local metabolites on cerebral arterioles
- E.
Histamine on skeletal muscle arterioles
- 19.The greatest pressure decrease in the circulation occurs across the arterioles because
- A.
They have the greatest surface area
- B.
They have the greatest cross-sectional area
- C.
The velocity of blood flow through them is the highest
- D.
The velocity of blood flow through them is the lowest
- E.
They have the greatest resistance
- 20.Pulse pressure is
- A.
The highest pressure measured in the arteries
- B.
The lowest pressure measured in the arteries
- C.
Measured only during diastole
- D.
Determined by stroke volume
- E.
Decreased when the capacitance of the arteries decreases
- 21.
- A.
Aorta
- B.
Central vein
- C.
Pulmonary artery
- D.
Right atrium
- E.
Renal artery
- 22.During which phase of the cardiac cycle is ventricular volume lowest?
- A.
Atrial systole
- B.
Isovolumetric ventricular contraction
- C.
Rapid ventricular ejection
- D.
Reduced ventricular ejection
- E.
Isovolumetric ventricular relaxation
- 23.The physiologic function of the relatively slow conduction through the atrioventricular node is to allow sufficient time for
- A.
Runoff of blood from the aorta to the arteries
- B.
Venous return to the atria
- C.
Filling of the ventricles
- D.
Contraction of the ventricles
- E.
Repolarization of the ventricles
- 24.Which of the following parameters is decreased during moderate exercise?
- A.
Arteriovenous O2 difference
- B.
Heart rate
- C.
Cardiac output
- D.
Pulse pressure
- E.
Total peripheral resistance (TPR)
- 25.Starling’s law of the heart
- A.
Does not operate in the failing heart
- B.
Does not operate during exercise
- C.
Explains the increase in heart rate produced by exercise
- D.
Explains the increase in cardiac output that occurs when venous return is increased
- E.
Explains the increase in cardiac output when the sympathetic nerves supplying the heart are stimulated
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