Ch.20 The Cardiovascular System: The Heart

Where in the conduction system do action potentials propagate most slowly?

Action potentials propagate most slowly through the AV node.

What is the significance of an enlarged Q wave?

An enlarged Q wave may indicate a myocardial infarction (heart attack).

Which diagnostic procedure for CAD is used to visualize coronary blood vessels?

Coronary angiography is used to visualize many blood vessels.

What is the role of HDL?

HDL removes excess cholesterol from body cells and transports it to the liver for elimination.

Which patients are candidates for cardiac transportation?

Individuals with end-stage heart failure or severe coronary artery disease are candidates for cardiac transplantation.

When is the partitioning of the heart complete?

Partitioning of the heart is complete by the end of the fifth week.

What constitutes pulmonary circulation? What constitutes systemic circulation?

Pulmonary circulation: the right ventricle thru the left atrium. Systemic circulation: left ventricle through the right atrium.

Which four developmental defects occur in tetralogy of Fallot?

Tetralogy of Fallot involves an inter ventricular septal defect, an aorta that emerges from both ventricles, a stenosed pulmonary valve, and an enlarged right ventricle.

How much blood remains in each ventricle at the end of ventricular diastole in a resting person? What is this volume called?

The amount of blood in each ventricle at the end of ventricular diastole ~ called the end-diastolic volume~ is about 130 mL in a resting person.

Which coronary blood vessel delivers oxygenated blood to the walls of the left atrium and the left ventricle?

The circumflex artery delivers oxygenated blood to the left atrium and left ventricle.

The coronary sulcus forms an external boundary between which chambers of the heart?

The coronary sulcus forms a boundary between the atria and ventricles.

How does the duration of an action potential in a ventricular contractile fiber compare with that in a skeletal muscle fiber?

The duration of an action potential is much longer in a ventricular contractile fiber (0.3 sec = 300 msec) than in a skeletal muscle fiber ((1-2 msec).

In what two ways does the fibrous skeleton contribute to the functioning of heart valves?

The fibrous skeleton attaches to the heart valves and prevents overstretching of the valves as blood passes through them.

Which heart sound is related to blood turbulence associated with closure of the AV valves?

The first heart sound (S1), or lubb, is associated with closure of the AV valves.

How does the thickness of the myocardium relate to the workload of a cardiac chamber?

The greater the workload, the thicker its myocardium.

When during embryonic development does the primitive heart begin to contract?

The heart begins to contract by the 22nd day of gestation.

What are the functions of intercalated discs in cardiac muscle fibers?

The intercalated discs hold the cardiac muscle fibers together and enable action potentials to propagate from one muscle fiber to another.

What is the mediastinum?

The mediastinum is the anatomical region that extends from the sternum to the vertebral column, from the first rib to the diaphragm, and between the lungs.

Which component of the conduction system provides the only electrical connection between the atria and the ventricles?

The only electrical connection between the atria and the ventricles is the atrioventricular bundle.

How do papillary muscles prevent atrioventricular valve cusps from everting (swinging upward) into the atria?

The papillary muscles contract, which pulls on the chord tendinae and prevents cusps of the AV valves from everting and letting blood flow back into the atria.

When you are exercising, contraction of skeletal muscles helps return blood to the heart more rapidly. Would this tend to increase or decrease stroke volume?

The skeletal muscle "pump" increase stroke volume by increasing preload (end-diastolic volume).

Which region of the heart is innervated by the sympathetic division but not by the parasympathetic division?

The ventricular myocardium receives innervation from the sympathetic division only.

Which layer is both a part of the pericardium and a part of the heart wall?

The visceral layer of the serous pericardium (epicardium) is both a part of the pericardium and a part of the heart wall.

Why is ventricular fibrillation such a serious arrhythmia?

Ventricular fibrillation is such a serious arrhythmia because ventricular pumping stops, blood ejection ceases, and circulatory failure and death can occur without immediate medical intervention.