Based on the typical shapes of ECG waves, which wave does this 11th cardiac cycle most resemble?
answer
QRS complex
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Would you call this QRS early, on time, or late compared to when other QRS complexes are formed?
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early
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Which of the following would increase cardiac output to the greatest extent?
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increased heart rate and increased stroke volume.
* cardiac output = heart rate x stroke volume.
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Which of the following would increase heart rate?
answer
epinephrine and norepinephrine
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How would an increase in the sympathetic nervous system increase stroke volume?
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increased contractility.
* by increasing available calcium), thus increasing stroke volume. Contractility causes an increase in stroke volume by decreasing end systolic volume; it does not change end diastolic volume.
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By what mechanism would an increase in venous return increase stroke volume?
answer
increased end diastolic volume.
* an increase in venous return increases the end diastolic volume. The fibers are stretched more, resulting in an increase in the force of contraction (preload, or the Frank-Starling Mechanism).
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How would a decrease in blood volume affect both stroke volume and cardiac output?
answer
decreased stroke volume and no change in cardiac output.
* ecreased blood volume would decrease the end diastolic volume, thus lowering the stroke volume. Although this would initially lead to a decrease in the cardiac output, heart rate would increase because of increased activity of the sympathetic nervous system in an effort to maintain cardiac output.
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Which blood vessels have the lowest blood pressure?
answer
Veins
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Through which valve must blood pass as it moves from the right atrium to the right ventricle?
answer
Tricuspid
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Which of these is the best definition of an artery?
answer
A vessel that carries blood away from the heart
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Most of the oxygen exiting the blood and entering the tissues does so from the ________.
answer
capillaries
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Arteries are most accurately defined as blood vessels that ________.
answer
carry blood away from the heart
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Along with nutrients, hormones, water, and gases, the cardiovascular system also transports _____________
answer
immune cells, cellular wastes, heat.
* All of these substances are transported by the cardiovascular system.
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Which of the following is the best definition of an artery?
answer
a vessel that carries blood away from the heart
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Which blood vessels return blood to the heart?
answer
veins
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Why does blood flow through the cardiovascular system?
answer
Because the heart establishes a pressure gradient
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As blood flows away from the heart, how does overall blood pressure in vessels change? Why?
answer
Blood pressure decreases, because of the effects of friction between the vessel walls and the moving blood.
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Consider three blood vessel segments of equivalent length and diameter: vessels A, B, and C.
Pressure at the beginning of each segment is as follows:
A) P = 100 mmHg;
B) P = 80 mmHg;
C) P = 60 mmHg.
Pressure at the end of each segment is as follows:
A) P = 70 mmHg;
B) P = 50 mmHg;
C) P = 30 mmHg.
Which vessel has the greatest blood flow through the described segment?
answer
Flow rate is the same in all three segments.
All three vessels have the same resistance and the pressure gradient is the same in all three segments: A) ?P = 100 - 70 = 30 mmHg; B) ?P = 80 - 50 = 30 mmHg; C) ?P = 60 - 30 = 30 mmHg.
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Why does the pressure in the arteries and arterioles fall as the blood moves away from the heart?
answer
Friction causes a loss of energy.
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Which of these would cause an increase in blood flow through a vessel?
answer
Vasodilation
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What is an advantage to the longer duration of cardiac action potential compared to the skeletal muscle action potential?
answer
The longer duration prevents tetanic contraction, which ensures that the heart chambers will relax and refill with blood before the next contraction.
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What is the role of heart valves?
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Heart valves ensure one-way flow of blood through the heart chambers.
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Which cells act as the heart's pacemaker? Why are they the pacemaker cells?
answer
Cells of the SA node are the usual pacemaker, because they are autorhythmic cells and set the pace of the heart rate.
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In skeletal muscle cells, action potentials cause the release of calcium from the SR by directly opening SR voltage-gated calcium channels. What causes the release of calcium from the SR in cardiac muscle cells?
answer
Influx of extracellular calcium ions opens ryanodine receptors allowing Ca2+ to flow out of the SR.
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Calcium ions are removed from the sarcoplasm of the cardiac cell by the action of the sarcoplasmic reticulum (SR) Ca2+-ATPase pump and which other mechanism?
answer
sodium-calcium exchanger on the sarcolemma
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The autorhythmicity of cardiac pacemaker cells is made possible by the reduced permeability of _______.
answer
potassium
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The repolarization of cardiac muscle is due to _______
answer
potassium exiting the cell
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The total refractory period of cardiac muscle _______.
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is longer than the total refractory period for skeletal muscle
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Skeletal muscle is capable of which of the following?
answer
wave summation and fused tetanus
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When the cardiac muscle cell is at rest, the concentration of _____________ is greater on the outside of the cell.
answer
sodium and calcium
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Modifiers that affect the force of contraction of the heart are _______.
answer
inotropic
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The movement of _______________ into the cardiac muscle cell depolarizes the cardiac muscle cell.
answer
sodium and calcium
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Modifiers that affect heart rate are _______.
answer
chronotropic
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The electrocardiogram represents ________.
answer
the electrical activity of all of the cardiac muscle cells
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Which two mechanisms influence the force of cardiac contraction?
answer
End diastolic volume and sympathetic nervous system stimulation
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Which of the following statements best describes the electrical events recorded by an ECG?
answer
the sum of the electrical activity of all cells in the heart
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An intracellular recording of electrical activity in either a contractile cell or autorhythmic cell is known as a(n)
answer
Action potential
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An extracellular recording of electrical activity of both autorhythmic and contractile cells of the heart is known as a(n)
answer
Electrocardiogram
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An electrode placement technique that uses three leads in order to record an electrocardiogram.
answer
Einthovens Triangle
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A two electrode pair constitutes a __________ which records the electrical activity of the heart.
answer
Lead
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Conduction through the atrioventricular (AV) node
answer
PR segment
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QRS complex
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Ventricular depolarization
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Ventricular repolarization
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T wave
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Atrial depolarization
answer
P wave
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Conduction through the atrioventricular (AV) bundle
answer
Q wave
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The ventricles are in their depolarized state
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ST segment
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Total time it takes for the ventricular muscle to depolarize and repolarize
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QT interval
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Which portion of a normal ECG represents ventricular depolarization?
answer
QRS complex
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Which of the following events is NOT represented on an ECG?
answer
atrial repolarization
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Ordering Electrical and Mechanical Events of the Heart
The anatomy of the intrinsic conduction system causes contraction of the ventricles to begin at the apex and move superiorly. Why is this important?
answer
so blood is forced upward, toward the semilunar valves
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The beginning of the QRS complex of the electrocardiogram (ECG) immediately precedes which of the following events?
answer
closing of the atrioventricular valves
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Which of the following can be heard with a stethoscope most easily?
answer
Closing of atrioventricular valves.
* The first heart sound, often described as a lubb, corresponds to the closing of the atrioventricular valves. The second heart sound is a sharper and crisper dupp that corresponds to the closing of the semilunar valves. Consequently, the two heart sounds mark the beginning and the end of ventricular systole.
question
Calculate the cardiac output if heart rate (HR) is 90 beats per minute, stroke volume (SV) is 110 ml/beat, end diastolic volume (EDV) is 140 ml, and end systolic volume (ESV) is 30 ml.
answer
9.9 L/min
* Cardiac output is the product of heart rate times stroke volume. Cardiac output increases to meet increased metabolic demand, often by increasing both heart rate and stroke volume at the same time. This occurs, for example, during maximal exercise, when cardiac output may increase to four or five times the resting level.
question
An increase in sympathetic stimulation of the heart would increase stroke volume by increasing __________.
answer
contractility.
* Increased sympathetic activity increases heart contractility. This causes cardiac fibers to contract more forcefully at all levels of preload. Regardless of end diastolic volume, this mechanism increases stroke volume by reducing end systolic volume.
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Stroke volume (SV):
answer
the volume of blood per heart beat pumped out by one ventricle
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Cardiac output (CO):
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the volume of blood per minute pumped out by one ventricle
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Heart rate (HR):
answer
the number of heart beats per minute
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End diastolic volume (EDV):
answer
the volume of blood in one ventricle before contraction
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Venous return (VR):
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the volume of blood per minute flowing into one atrium
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End systolic volume (ESV):
answer
the volume of blood in one ventricle after contraction
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The balance between parasympathetic and sympathetic stimulation to the heart controls heart rate.
As part of a blood drive on campus for the American Red Cross, you and your friends have just donated 500 ml of blood. You are now relaxing at the student lounge, waiting for A lab to begin. Unfortunately, even though you are thirsty, you haven't bothered to buy yourself a drink. Other than a little soreness of the skin and tissue around your median cubital vein, you feel fine. How has your 500 ml decrease in blood volume most likely affected your cardiac output, heart rate, and stroke volume?
answer
no change in cardiac output, increased heart rate, decreased stroke volume
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Arrange these elements of the intrinsic conduction system in the order that a depolarizing impulse travels during a normal heartbeat.
answer
first element depolarized
* SA node
* Internodal pathways
* AV node
* AV bundle
* Bundle branches
* Purkinje fibers
last element depolarized
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Purkinje fibers:
answer
Convey(s) the impulse throughout the ventricular walls
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Bundle branches:
answer
Convey(s) the impulse down the interventricular septum
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AV node:
answer
Delay(s) occurs here while atria contract
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AV bundle :
answer
Electrical link(s) between atria and ventricles
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Internodal pathways:
answer
Link(s) between the SA node and AV node
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SA node:
answer
Set(s) the pace for the entire heart
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Which part of the intrinsic conduction system normally initiates the depolarizing impulse that causes a heartbeat?
answer
SA node
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Which of these structures conduct(s) action potentials the slowest?
answer
AV node
* Action potentials slow down as they pass through the AV node. This gives the atria time to finish contracting before the ventricles are depolarized
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The effect of the sympathetic nervous system on the heart is to _______.
answer
increase the heart rate and increase the force of contraction
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Which branch of the autonomic nervous system dominates after a large meal?
answer
the parasympathetic branch
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The sinoatrial node is located _______.
answer
in the right atrial wall of the human heart
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Excessive vagal stimulation of the heart will result in _______.
answer
a decrease in heart rate and, eventually, a temporary cessation of the heartbeat
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Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during __________.
answer
ventricular diastole
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Which of the following is correct about the filling of the ventricles?
answer
most blood flows passively into the ventricles through open AV valves.
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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
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What causes the aortic semilunar valve to close?
answer
greater pressure in the aorta than in the left ventricle
question
Put the phases of the cardiac cycle in the correct order, starting after ventricular filling.
