Question :
31.Fibrillation the
a.backflow of blood throughout the heart
b.coordinated function of nodal : 1417114
31.Fibrillation is the
a.backflow of blood throughout the heart
b.coordinated function of nodal cells
c.failure of the heart valves to function
d.flow of blood through the heart's fibrous skeleton
e.uncoordinated excitation and contraction of cardiac cells
32.The AV node
a.is the normal pacemaker of the heart
b.is the only electrical connection between the atria and the ventricles
c.rapidly conducts impulses from the atria to the ventricles so that they contract simultaneously
d.is not innervated by the vagus nerve
e.has the slowest rate of depolarization in the heart
33.The electrocardiogram is most useful in determining which component of cardiac output?
a.stroke volume
b.heart rate
c.ejection fraction
d.end-diastolic volume
e.murmurs
34.An ectopic focus is the place where
a.an abnormally excitable area of the heart initiates a premature action potential
b.all of the electrical impulses of the heart terminate normally
c.an ECG lead is attached on the outside of the chest
d.a heart valve is attached
e.the chordae tendineae attach to a valve
35.The function of the ventricular conduction system of the heart is to
a.spread the action potential throughout the ventricle to ensure a single, coordinated contraction of the both ventricles
b.spread the action potential in the absence of sympathetic stimulation
c.spread the action potential throughout the atria and ventricles
d.slow down the original action potential so it has time to spread through the ventricles evenly
e.perform both a and d
36.The refractory period of cardiac muscle
a.lasts almost as long as the contraction period
b.is much longer than the refractory period in skeletal muscle
c.prevents tetanic contraction of the heart to occur to ensure smooth, coordinated ejection of blood from the ventricles
d.is important for all of the above reasons
e.is important for only reasons a and b
37.The membrane potential of cardiac contractile cells at rest is about ____ mV.
a.-110
b.-90
c.-70
d.-50
e.-30
38.Why can't tetanus occur in the heart?
a.There are no distinct motor units in the heart.
b.There is inadequate oxygen supply via the coronary circulation to metabolically support a sustained contraction.
c.The refractory period in cardiac muscle lasts almost as long as the contraction.
d.The heart contracts with maximal force every beat so it is impossible to increase the strength of its contraction.
e.Vagal stimulation slows down the heart rate to prevent summation of contractions.
39.During isovolumetric phases of the cardiac cycle,
a.the atria are contracting
b.all heart valves are closed
c.blood is being ejected into the aorta
d.the ventricles can only be relaxing
e.both a and b are true
40.The volume of blood ejected from each ventricle during a contraction is called the
a.end-diastolic volume
b.end-systolic volume
c.stroke volume
d.cardiac output
e.cardiac reserve
