CHAPTER 17

Which is a normal excitation pathway? (Select all that apply.) A. AV node B. SA node C. VA node D. Bundle of HIS E. Purkinje Fibers

A. AV node B. SA node D. Bundle of HIS E. Purkinje Fibers The AV node, SA node, Bundle of HIS, and Purkinje fibers are normal excitation pathways. There is no VA node in the heart.

What valve directs blood flow from the left atrium to the left ventricle? A. Mitral B. Aortic C. Pulmonic D. Tricuspid

A. Mitral The mitral valve directs blood from the left atrium to the left ventricle. The aortic valve lies between the left ventricle and the aorta. The pulmonic valve lies between the right ventricle and the pulmonary arteries. The tricuspid valve directs blood from the right atrium to the right ventricle.

What is a major determinant of stroke volume? (Select all that apply.) A. Preload B. Afterload C. Heart rate D. Contractility E. Vagus nerve activation

A. Preload B. Afterload D. Contractility The preload applies a stretch on the myocardium much like a rubber band is loaded when it is stretched. Afterload is the pressure that the heart has to overcome to eject blood to the body. Contractility is the force with which the heart muscle contracts to force the blood out of the ventricle. Together these three factors are the main determinants of stroke volume. Heart rate is controlled primarily by the autonomic nervous system and is not considered a determinant of stroke volume. Activation of the vagus nerve will decrease heart rate but not directly affect stroke volume.

Blood flows in the human body move from which of the following? (Select all that apply.) A. Right atrium to the right ventricle B. Right ventricle to the lungs C. Left ventricle to the body D. Lungs to the left atrium E. Body to the left atrium

A. Right atrium to the right ventricle B. Right ventricle to the lungs C. Left ventricle to the body D. Lungs to the left atrium Un-oxygenated blood flows into the right atrium and then into the right ventricle. The right ventricle pumps the blood through the pulmonary valve to the lungs. The blood is pumped through the mitral valve to the left ventricle, which pumps the blood through the aortic valve into the aorta and to the body. The blood returns to the heart from the lungs into the left atrium. The blood returns from the body to the right atrium.

What portion(s) of the heart does the left anterior descending branch supply? (Select all that apply.) A. Septal B. Apical C. Anterior D. Lateral E. Posterior

A. Septal B. Apical C. Anterior The left anterior descending branch supplies the septal and apical portions of the heart. The left anterior descending branch supplies the anterior portion of the heart. The left circumflex supplies the lateral and posterior left ventricles.

Which wave corresponds with the AV valve bulging during ventricular contraction? A. A wave B. C wave C. D wave D. V wave

B. C wave The C wave corresponds with the AV valve bulging during ventricular contraction. The A wave corresponds with atrial contraction. There is no D wave. The V wave corresponds to atrial filling.

Which terms refers to an increased speed of conduction? A. Inotropic B. Dromotropic C. Chronotropic D. Acetylcholine

B. Dromotropic Dromotropic refers to increased speed of conduction. Inotropic refers to increased contractile force. Chronotropic refers to increased heart rate. Acetylcholine is a neurotransmitter for the nervous system.

Which phase of cardiac action potential is caused by closure of the fast sodium channels? A. Phase 0 B. Phase 1 C. Phase 2 D. Phase 3

B. Phase 1 Phase 1 is a small repolarizing deflection that corresponds to closure of the fast sodium channel. Phase 0 begins when fast sodium channels open. Phase 2 is the plateau phase. Phase 3 is characterized by rapid return of the resting membrane potential.

What is the name for the arrangement in which separate cells of the myocardium can function together? A. Autoregulation B. Syncytium C. Ischemia D. Myocyte

B. Syncytium A functional syncytium is an arrangement in which separate cells of the myocardium function together in a coordinated manner. Autoregulation is the ability of the arteries to adjust blood flow according to tissue needs. Ischemia is a disruption of blood flow to cardiac tissues. A myocyte is a cardiac cell.

The part of the cardiac cycle in which the cardiac muscle obtains oxygen and rids itself of waste products is the A. systole. B. diastole. C. ventricular ejection. D. isovolumic contraction.

B. diastole. The heart muscle relaxes and allows blood to flow through it as it relaxes and fills passively during diastole. The heart muscle contract to move blood through the chambers during systole. Ventricular ejection refers to the blood being moved out of the ventricles. Mechanically, the isovolumic phase of ventricular systole is defined as the interval between the closing of the AV valves and the opening of the semilunar valves.

The layer of squamous cells that lines the cardiac chambers and valves is called the A. myocardium. B. endocardium. C. epicardium. D. pericardium.

B. endocardium. The endocardium lines the valves and chambers with squamous cells. The myocardium refers to the heart muscle. The epicardium is the outer layer of epithelial cells that is part of the pericardium. The pericardium is the protective covering around the heart.

Myocytes leak the enzyme creatine kinase (CK) into the bloodstream in response to cell A. growth. B. ischemia. C. maturation. D. reproduction.

B. ischemia. The cell walls of the myocyte become leaky when they do not have enough energy because they lack nutrients or oxygen. This lack of nutrients and oxygen causes the cell to lose creatine kinase (CK) into the bloodstream and can be diagnostic of heart damage. CK is not leaked into the bloodstream as a result of cell growth, maturation, or cell reproduction.

The structure that is composed of six polypeptide chains, two heavy chains, and four light chains is called A. actin. B. myosin. C. troponin. D. tropomyosin.

B. myosin. Myosin is composed of six polypeptide chains. These light and heavy chains are organized into a tail region and two globular "head" areas. The myosin heads interact with actin filaments to produce muscle contraction. Thin filaments are composed of three different proteins that include actin. Troponin is a regulatory protein that controls the activities of actin and myosin filaments. Tropomyosin is a regulatory protein that controls the activities of actin and myosin filaments.

Which electrolyte is necessary for muscle contraction? A. K+ (potassium) B. Na+ (sodium) C. Ca2+ (calcium) D. Mg2+ (magnesium)

C. Ca2+ (calcium) Ca2+ is necessary for muscle contraction. K+ and Na+ are necessary for the sodium-potassium pump. Mg2+ is essential for all life as a cofactor for ATP.

Which statement is true regarding the vagus nerves? A. The left vagus nerve supplies the SA node. B. Parasympathetic nerves innervate all of the ventricles. C. Parasympathetic nerve stimulation reduces the heart rate. D. The right vagus nerve supplies both the SA and AV nodes.

C. Parasympathetic nerve stimulation reduces the heart rate. Parasympathetic nerves stimulate a reduction in heart rate. The left vagus nerve is part of the parasympathetic system and supplies the AV node. The parasympathetic system predominantly supplies the AV and SA nodes, which are located above the ventricles. The right vagus nerve supplies the SA node.

Which wave on the ECG is representative of depolarization of the lateral walls? A. Q wave B. R wave C. S wave D. T wave

C. S wave The S wave is representative of lateral wall depolarization. The Q wave represents septal depolarization. The R wave represents apical depolarization. The T wave represents ventricular repolarization.

Which statement is true regarding muscle contraction? A. Contraction of cardiac muscle results from lengthening of sarcomeres. B. Calcium removal from the cytoplasm causes contraction. C. Calcium entry into the cytoplasm causes relaxation. D. Cardiac myocytes are terminally differentiated.

D. Cardiac myocytes are terminally differentiated. Cardiac myocytes are terminally differentiated and cannot proliferate. Contraction of the myocyte results from shortening, not lengthening, of sarcomeres. Calcium removal from the cytoplasm causes relaxation, not contraction. Calcium entry in the cytoplasm is required for contraction; it does not cause relaxation.

Which refers to intermittent, spontaneous generation of action potentials? A. Relative refractory B. Antiarrhythmics C. Repolarization D. Rhythmicity

D. Rhythmicity Rhythmicity, otherwise known as automaticity, refers to intermittent, spontaneous generation of action potentials. Relative refractory is a period in phase 3 when sodium channels may open but when a larger than normal depolarization stimulus is required. Antiarrhythmics are used to affect action potentials. Sodium channels begin to open as the membrane potential becomes more negative during repolarization phase.

The echocardiogram is especially useful in the measurement of the A. coronary blood flow. B. structures of the lungs. C. obstructions to blood flow. D. heart motion within the chest.

D. heart motion within the chest. Echocardiography uses reflected sound waves (ultrasound) to provide an image of cardiac structure and motion within the chest. Coronary blood flow is best seen with a cardiac catheterization. The structures and function of the lungs can be seen in a chest x-ray film, in a computed tomography scan, and with pulmonary function testing. Coronary obstructions to blood flow are best seen with a cardiac catheterization.