VAP 18.8-18.14
Which factor affecting stroke volume (SV) is correct? ANSWER: The greater the contractility, the smaller the ESV. When venous return increases, SV decreases. Increase in filling time decreases the EDV. Vasodilation increases afterload.
a
Which of the following would be greater? ANSWER: the end-diastolic volume when the heart rate is 60 beats/minute the end-diastolic volume when the heart rate is 150 beats/minute
a
In cardiac muscle ANSWER: calcium ions play no role in the process of contraction. calcium ions enter the cell through slow ion channels. calcium ions are not released from the sarcoplasmic reticulum. calcium ions do not bind to troponin molecules. calcium ions play an important role in repolarizing the membrane after the depolarization phase.
b
Action potentials generated by the autorhythmic cells spread to the contractile cells through what structures in the membrane? ANSWER: gap junctions desmosomes tight junctions intercalated discs
a
Depolarization of the ventricles is represented on an electrocardiogram by the ANSWER: QRS complex. S wave. P wave. PR complex. T wave.
a
Describe the pressures in the atria and ventricles that would cause the opening of the AV valves. ANSWER: Pressure in the atria would be greater than the pressure in the ventricles. Pressure in the ventricles would be greater than in the atria. Pressures in the atria and ventricles would be equal.
a
In an ECG recording, which of the following coincides with ventricular repolarization? ANSWER: T wave P-R interval P wave QRS complex
a
Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during __________. ANSWER: ventricular diastole ventricular systole
a
What causes the aortic semilunar valve to close? ANSWER: greater pressure in the aorta than in the left ventricle higher ventricular pressure than aortic pressure equal ventricular and aortic pressures
a
What does the ECG wave tracing represent? ANSWER: electrical activity in the heart contraction of the heart
a
What occurs at "B" on the graph? ANSWER: semilunar valve closes end-systolic volume AV valve closes semilunar valve opens
a
The contraction phase of the cardiac cycle is called ________.
systole
In order to cause cardiac muscle contraction, the contractile cells must also depolarize. What causes the depolarization of the contractile cells? ANSWER: the flow of negative ions from adjacent cells the flow of positive ions from adjacent cells an unstable resting membrane potential in the contractile cells
b
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? ANSWER: calcium potassium sodium
b
Stroke volume depends on ANSWER: end-diastolic volume. the contractility of the ventricle. the pressure required to pump blood into the aorta. all of the above none of the above
d
The AV node delivers the stimulus to the AV bundle, located within the interventricular septum. ANSWER: The first part of the statement is false but the second part is true. The first part of the statement is true but the second part is false. Both parts of the statement are false. Both parts of the statement are true.
d
The first heart sound is heard when the ANSWER: blood enters the aorta. atria contract. AV valves open. AV valves close. semilunar valves close.
d
Put the phases of the cardiac cycle in the correct order, starting after ventricular filling. ANSWER: ventricular ejection, isovolumetric contraction, isovolumetric relaxation isovolumetric contraction, ventricular ejection, isovolumetric relaxation isovolumetric relaxation, ventricular ejection, isovolumetric contraction ventricular ejection, ventricular relaxation, isovolumetric contraction
b
What does the QRS complex represent in the ECG wave tracing? ANSWER: ventricular repolarization ventricular depolarization atrial depolarization atrial repolarization
b
When threshold is reached at the SA node (an autorhythmic cell), what channels open causing further depolarization of the membrane? ANSWER: potassium fast calcium slow calcium fast sodium
b
Which of the following is correct about the filling of the ventricles? ANSWER: The majority of ventricular filling is caused by contraction of the atria. Most blood flows passively into the ventricles through open AV valves.
b
As a result of the long refractory period in the cardiac action potential, cardiac muscle cannot exhibit ANSWER: tonus. treppe. tetany. recruitment. fatigue.
c
Contraction of the atria results from which wave of depolarization on the ECG tracing? ANSWER: QRS complex T wave P wave
c
Increased pressure in the ventricles would close what valve(s)? ANSWER: both semilunar and AV valves semilunar valves only AV valves only
c
The heart pumps approximately ________ milliliters of blood each minute. ANSWER: 100,000 15,000 6,000 50,000 20,000
c
The volume of blood ejected from each ventricle during a contraction is called the ANSWER: end-diastolic volume. end-systolic volume. stroke volume. cardiac reserve. cardiac output.
c
Which part of the conduction system initiates the depolarizing impulse, which spreads throughout the heart? ANSWER: Purkinje fibers AV bundle (bundle of His) SA node AV node
c
Which part of the intrinsic conduction system delays the impulse briefly before it moves on to the ventricles? ANSWER: Purkinje fibers SA node AV node AV bundle (bundle of His) bundle branches
c
Each of the following factors will increase cardiac output, except ANSWER: increased sympathetic stimulation. increased venous return. increased heart rate. increased parasympathetic stimulation. both increased venous return and increased parasympathetic stimulation.
d
Repolarization of an autorhythmic cell is due to the opening of which channels? ANSWER: chemically gated calcium channels Chemically gated potassium channels voltage-gated sodium channels voltage-gated potassium channels
d
The long plateau phase of the cardiac muscle action potential is due to ANSWER: increased membrane permeability to potassium ion. movement of fewer sodium ions across the cell membrane into the cell. decrease in the amount of calcium diffusing across the membrane. calcium channels remaining open. increased membrane permeability to sodium ions.
d
The normal pacemaker of the heart is located in the ANSWER: Purkinje fibers. atrioventricular node. wall of the left ventricle. sinoatrial node. both the left and right ventricles.
d
What occurs at the area labeled "D" on the graph? ANSWER: AV valve opens diastolic refilling begins semilunar valve opens both AV valve opens and diastolic refilling begins both semilunar valve opens and diastolic refilling begins
d
_______ is to slow heart rate as ________ is to fast heart rate. ANSWER: Bradycardia; cardiomyopathy Cardiac tamponade; bradycardia Tachycardia; bradycardia Bradycardia; tachycardia none of the above
d
If there is a complete block between the SA node and the AV node, how would the ECG be affected? ANSWER: The QRS duration will be longer. There will be much bigger P waves. The P-R interval will be shorter. The ventricles will stop beating. The rate of P waves will be faster than the rate of QRS complexes.
e
The P wave of the electrocardiogram is a signal from ANSWER: depolarization of the SA node. repolarization of the atria. depolarization of the AV node. depolarization of the ventricles. depolarization of the atria.
e
The cardioacceleratory center activates sympathetic neurons and the cardioinhibitory center controls parasympathetic neurons. ANSWER: The first part of the statement is true but the second part is false. The first part of the statement is false but the second part is true. Both parts of the statement are true. Both parts of the statement are false. Both parts of the statement are true and relate to brainstem control of heart rate.
e
