17.3 - 17.4
Which of the following statements describes the total refractory period of cardiac muscle?
It is longer than the total refractory period for skeletal muscle.
High-pressured blood in the ventricles ________.
forces the semilunar valves open
What two values are needed to calculate cardiac output (CO) for a ventricle?
Stroke volume (SV) and heart rate (HR)
Which of the following events is not part of the cardiac cycle?
Atrial contraction phase
What largely determines preload?
End-diastolic volume (EDV)
Which wave on the electrocardiogram (ECG) represents ventricular depolarization?
QRS complex
During what phase is the S1 heart sound first heard?
Isovolumetric contraction phase
Approximately how much blood is pumped from each ventricle during the ventricular ejection phase?
70 ml
Which hormone decreases cardiac output by decreasing blood volume and preload?
Atrial natriuretic peptide
Approximately how much blood is pumped from each ventricle during the ventricular ejection phase?
ml
Which of the following events can be heard most easily with a stethoscope?
Closing of atrioventricular valves
The degree of stretch experienced by the sarcomeres in the ventricle cells before they contract is called __________.
Preload
Calculate the end-systolic volume (ESV) if the end-diastolic volume (EDV) in a resting heart is 110 ml and stroke volume (SV) is 70 ml.
40 ml
What percentage of atria blood flows passively into the ventricles?
80 %
Which wave on the electrocardiogram (ECG) corresponds with the ventricular filling phase of the cardiac cycle?
P Wave
What is the volume of blood pumped out by one ventricle per heart beat?
Stroke Volume (SV)
Which of the following factors would increase cardiac output to the greatest extent?
Increased heart rate and increased stroke volume
Which of the following paths does an action potential in the heart normally take?
SA node atrial contractile cells AV node where it is delayed AV bundle right and left bundle branches Purkinje fibers ventricular contractile cells
Which of the following chemical messengers decreases heart rate?
Acetylcholine
Which chamber generates the highest pressure during systole?
Left Ventricle
Inotropic agents affect __________.
contractility
Which of the following terms refers to the force the ventricles must overcome to eject blood into their respective arteries?
Afterload
Which of the following hormones decrease cardiac output by decreasing blood volume and preload?
Atrial natriuretic peptide
Which cranial nerves have a negative chronotropic effect on heart rate?
Vagus nerves (CN X)
According to the Frank-Starling law, a bigger preload will result in __________.
a stronger contraction