How would an increase in the sympathetic nervous system increase stroke volume?
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An increase in sympathetic nervous system activity would increase contractility (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?
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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?
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a decreased 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 a effort to maintain cardiac output.
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Which blood vessels have the lowest blood pressure?
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Veins
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Through which valve must blood pass as it moves from the right atrium to the right ventricle?
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Tricuspid
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Which of these is the best definition of an artery?
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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
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Capillaries
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Arteries are most accurately defined as blood vessels that
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Carry blood away from the heart
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Which of the following is the best definition of an artery?
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A vessel that carries blood away from the heart
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Which blood vessels return blood to the heart?
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Veins
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Why does blood flow through the cardiovascular system?
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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?
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Blood pressure decreases, because of the effects of friction between the vessels walls and the moving blood.
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Why does the pressure in the arteries and arterioles fall as the blood moves away from the heart?
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Friction causes a loss of energy
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Which of these would cause an increase in blood flow through a vessel?
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Vasodilation
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Most of the oxygen exiting the blood and entering the tissues does so from the
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Capillaries
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Along with nutrients, hormones, water, and gases, the cardiovascular system also transports
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heat, immune cells, and cellular wastes
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What is an advantage to the longer duration of cardiac action potential compared to the skeletal muscle action potential?
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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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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?
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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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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
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Cells of the SA Nodes are the usual pacemaker, because they are autorhythmic cells and set the pace of the heartrate
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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?
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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 sarcoplasmic reticulum (SR) Ca2+-ATPase pump and which other mechanism?
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Sodium- calcium exchanger on the sarcolemma
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The autorhythmicity of cardiac pacemaker cells is made possible by the reduced permeability of
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Potassium
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The repolarization of cardiac muscle is due to
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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 of skeletal muscles
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Skeletal muscles is capable of which of the following
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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 cells
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Sodium and calcium
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Modifiers that affect the force of contraction of the heart are _______.
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Inotropic
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The movement of _____ into the cardiac muscle cell depolarizes the cardiac muscle cell.
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Sodium and calcium
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Modifiers that affect heart rate are ____
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Chronotropic
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The electrocardiogram represents ______.
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The electrical activity of all of the cardiac muscle cells
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Which two mechanisms influence the force of cardiac contraction?
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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?
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The sum of the electrical activity of all cells of the body.
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An extracellular recording of electrical activity of both autorhythmic and contractile cells of the heart is known as a(n)
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Electrocardiogram
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An intracellular recording of electrical activity in either a contractile cell or autorhythmic cell is known as a(n) .
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Action potential
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________________is an electrode placement technique that uses three leads in order to record an electrocardiogram.
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Einthoven's triangle
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A two electrode pair constitutes a ______, which records the electrical activity of the heart.
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Lead
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The anatomy of the intrinsic conduction system causes contraction of the ventricles to begin at the apex and move superiorly. why is this important?
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So blood is forced upward, toward the semilunar valves
+++++Beginning contraction at the apex causes blood to be forced upward, through the semilunar valves, and into the aorta and pulmonary trunk. This makes ventricular ejection more efficient, much like squeezing a tube of toothpaste up from the bottom is more efficient at dispensing the toothpaste than is squeezing from the top.
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Which of the following can be heard with a stethoscope most easily?
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closing of the semilunar valves
closing of the atrioventricular valves
++++Heart sounds are an extremely helpful diagnostic tool that is not invasive. 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.
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The beginning of the QRS complex of the electrocardiogram (ECG) immediately precedes which of the following events?
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Closing of the atrioventricular valves
The QRS complex is a recording of ventricular depolarization. This depolarization begins just prior to the ventricular contraction it initiates. As the ventricles contract, the increase in ventricular pressure closes the atrioventricular valves, beginning isovolumetric contraction. As ventricular pressure increases above the corresponding blood vessel, only then do the semilunar valves open, initiating ventricular ejection.
.
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The P wave of the electrocardiogram begins right before __________.
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Atrial systole
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During resting conditions, the majority of ventricular filling is caused by _________.
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passive blood flow from the atrium
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What are the valve positions during isovolumetric contraction?
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The atrioventricular valves and semilunar valves are both closed.
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During the cardiac cycle, which phase comes after isovolumetric contraction?
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Ventricular ejection
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The heart sounds associated with the atrioventricular valves closing occur at __________.
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the start of ventricular systole
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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.
View Available Hint(s)
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9.9 L/min
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An increase in sympathetic stimulation of the heart would increase stroke volume by increasing __________.
View Available Hint(s)
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Contractibility
***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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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&P 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?
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Donating blood does not alter resting cardiac output. However, the decreased blood volume does decrease venous return and end diastolic volume. This decreases preload, thereby lowering stroke volume. By itself, decreased stroke volume would decrease cardiac output. But remember, the body still requires a resting blood flow of around 5 L/min. To meet this demand, homeostatic mechanisms quickly restore cardiac output to resting levels. For example, heart rate is increased as parasympathetic influence is removed and sympathetic activity is increased. Even though your blood volume is a bit low, your body has no problem compensating to meet your resting metabolic needs. Running away from a tiger? Now that might be a different story.
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