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The enlarged coronary vessel outside the heart that empties blood into the right atrium is the ________.
coronary sinus
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What structure in the fetal heart allows blood to flow from the right atrium directly to the left atrium?
foramen ovale
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The ECG T wave interval represents ________.
ventricular repolarization
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CO = ________ × SV.
HR or heart rate
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The ________ membrane covers the heart.
visceral layer of the serous pericardium
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The ________ valve of the heart has three valves with chordae tendineae.
tricuspid
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The ________ and ________ valves of the heart have no chordae tendineae attached.
aortic; pulmonary
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Define systole and diastole. Which heart chambers are usually referenced when these terms are used?
Systole is contraction of the muscle. Diastole is relaxation of the muscle. The contraction and relaxation of the ventricles are normally described with the terms systole and diastole.
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Define the terms end diastolic volume (EDV) and end systolic volume (ESV) and relate them to the calculation of stroke volume.
EDV is the amount of blood that collects in a ventricle during diastole. ESV is the volume of blood remaining in aventricle after it has contracted. Stroke volume (ml/beat) equals EDV - ESV.
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What is the difference between the auricles and the atria?
Auricles are the flaplike appendages attached to the atria that increase the atrial volume. The atria are receiving chambers for blood returning to the heart from the pulmonary and systemic circulation.
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The heart is called a "double pump" because there are two functionally separate circulations. Trace the pathway of each of these circulations and include the following information: heart chambers involved, major blood vessels involved, and general areas through which the blood flows. Begin with the right atrium.
Right atrium to right ventricle to pulmonary arteries to lungs (pulmonary circuit pump); pulmonary veins to left atrium to left ventricle to aorta to body tissues to venae cavae (systemic circuit pump).
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What two important functions does the cardiac conduction system perform?
The important functions of the cardiac conduction system are to initiate impulses (pacemaker) and to distribute impulses throughout the heart so that it depolarizes and contracts in an orderly, sequential manner.
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Explain autorhythmicity in cardiac muscle cells.
Autorhythmic cells do not maintain a stable resting membrane potential. Instead, they have an unstable resting potential that continuously depolarizes, drifting toward threshold for firing. These spontaneously changing membrane potentials, called pacemaker potentials, initiate the action potentials that trigger the heart’s rhythmic contractions.
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Why is oxygen so much more critical to the heart muscle than to skeletal muscles?
Cardiac muscle cells are highly dependent on oxygen and rely almost exclusively on aerobic respiration. Thus, they cannot incur much oxygen debt. When there is a forced switch to anaerobic respiration, lactic acid and rising H+ levels impair heart function.
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What is the functional importance of the intercalated discs of cardiac muscle? What is the functional importance of the fibrous skeleton of the heart?
Intercalated discs contain anchoring desmosomes that prevent cell separation, and gap junctions that allow ions to travel from cell to cell, transmitting current across the entire heart. The fibrous skeleton acts both as a tendon and an insertion, giving the cardiac cells something to pull or exert their force on.
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What is bradycardia?
Bradycardia is a heart rate slower than 60 beats per minute.
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Why is fibrosis of the cardiac muscle serious?
With fibrosis the heart muscle stiffens and is unable to fill the atria as it once did; therefore, less blood is pumped. Further, as the muscle stiffens it takes more energy to expel the bolus of blood from the heart, which will eventually weaken the heart.
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