Which of the following would increase cardiac output to the greatest extent?
increased heart rate and increased stroke volume
Which of the following would increase heart rate?
epinephrine and norepinephrine
How would an increase in the sympathetic nervous system increase stroke volume?
increased contractility
By what mechanism would an increase in venous return increase stroke volume?
increased end diastolic volume
How would a decrease in blood volume affect both stroke volume and cardiac output?
decreased stroke volume and no change in cardiac output
Which structure attaches the pulmonary trunk to the aortic arch?
ligamentum arteriosum
What occurs when the left ventricle contracts?
The distance between the base and apex decreases.
Which structure provides a rapid-conduction path that tenses the papillary muscles before the ventricular myocardium contracts?
moderator band
Which is true regarding coronary function?
The semilunar valves close before the AV valves open.
Balloon angioplasty:
is most effective in treating small, soft plaques.
In which phase does ventricular ejection (ventricular pressure rises and exceeds pressure in the arteries) occur?
ventricular systole - second phase
When observing pressure changes during the cardiac cycle, which occurs during the pressure tracing called dicrotic notch?
The semilunar valves close, and pressure rises again as the elastic arterial walls recoil during diastole.
Choose the correct order of events during the cardiac cycle.
2-1-5-4-6-3
Which cardiac event occurs latest in the cardiac cycle?
AV valves open; passive atrial filling occurs.
Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during __________.
ventricular diastole
Which of the following is correct about the filling of the ventricles?
Most blood flows passively into the ventricles through open AV valves.
Describe the pressures in the atria and ventricles that would cause the opening of the AV valves.
Pressure in the atria would be greater than the pressure in the ventricles.
What causes the aortic semilunar valve to close?
greater pressure in the aorta than in the left ventricle
Put the phases of the cardiac cycle in the correct order, starting after ventricular filling.
isovolumetric contraction, ventricular ejection, isovolumetric relaxation
Increased pressure in the ventricles would close what valve(s)?
AV valves only
Isovolumetric contraction is associated with which cardiac cycle phase?
ventricular systole - first phase
Which part of the conduction system initiates the depolarizing impulse, which spreads throughout the heart?
SA node
What does the ECG wave tracing represent?
electrical activity in the heart
What does the QRS complex represent in the ECG wave tracing?
ventricular depolarization
Contraction of the atria results from which wave of depolarization on the ECG tracing?
P wave
Which part of the intrinsic conduction system delays the impulse briefly before it moves on to the ventricles?
AV node
Each heartbeat begins with an action potential generated at which of the following?
sinoatrial (SA) node
Which of the following is a characteristic of the stage of rapid depolarization in a cardiac muscle cell?
A massive influx of sodium ions occurs.
Action potentials generated by the autorhythmic cells spread to the contractile cells through what structures in the membrane?
gap junctions
One of the changes that occurs in the pacemaker potential (unstable resting membrane potential) in the SA node (an autorhythmic cell) is a decreased efflux of what ion?
potassium
When threshold is reached at the SA node (an autorhythmic cell), what channels open causing further depolarization of the membrane?
fast calcium
Repolarization of an autorhythmic cell is due to the opening of which channels?
voltage-gated potassium channels
In order to cause cardiac muscle contraction, the contractile cells must also depolarize. What causes the depolarization of the contractile cells?
the flow of positive ions from adjacent cells
Sympathetic innervation of the heart:
arrives in postganglionic fibers within the cardiac nerves.
Which statement is correct regarding the intrinsic heart rate?
During parasympathetic stimulation, acetylcholine released by parasympathetic neurons opens chemically gated potassium channels in the plasma membrane.