front 1 Which phrase best describes the normal mechanical role of the atria? A. Strong afterload generators | back 1 B. Weak primer pumps |
front 2 A congenital lesion selectively impairs right ventricular outflow. Which circulation is most directly underfilled? A. Coronary circulation | back 2 C. Pulmonary circulation |
front 3 A patient in sinus rhythm has repeated, orderly heart contractions occurring without interruption. This ongoing sequence is best termed: A. Cardiac rhythmicity | back 3 A. Cardiac rhythmicity |
front 4 A physiology lab asks which grouping correctly lists the three major types of heart muscle. Which is correct? A. Atrial, Purkinje, papillary | back 4 C. Atrial, ventricular, conductive |
front 5 Compared with skeletal muscle, cardiac muscle contraction is most similar except for which feature being longer? A. Sarcomere width | back 5 B. Duration |
front 6 On microscopy, a student identifies the usual contractile myofibrillar elements of cardiac muscle. These are: A. Troponin and tropomyosin | back 6 C. Actin and myosin filaments |
front 7 Intercalated discs are best described as: A. Extracellular collagen partitions | back 7 B. Cell membranes between myocytes |
front 8 At the intercalated disc, adjacent cardiac cell membranes join to form structures that permit ionic current spread. These are: A. Tight occluding junctions | back 8 C. Permeable communicating junctions |
front 9 A toxic exposure disrupts gap junction function throughout the myocardium. Which immediate effect is most expected? A. Slower action potential spread | back 9 A. Slower action potential spread |
front 10 In a normal heart, the myocardium is functionally arranged into two major syncytia. These are: A. Endocardial and epicardial | back 10 D. Atrial and ventricular |
front 11 During dissection, a fibrous plane is identified encircling the atrioventricular valvular openings. This tissue normally separates the: A. Great arteries from atria | back 11 C. Atria from ventricles |
front 12 In the normal heart, impulses do not freely pass directly from one syncytium to the other because the atria and ventricles are separated by: A. Fatty connective septa | back 12 B. Fibrous tissue |
front 13 The normal separation of atrial and ventricular syncytia provides which mechanical advantage? A. Simultaneous chamber ejection | back 13 B. Ventricles fill after atria contract |
front 14 When a standard fast-response cardiac action potential is recorded for teaching purposes, it is classically taken from a: A. Ventricular muscle fiber | back 14 A. Ventricular muscle fiber |
front 15 A ventricular myocyte action potential is measured from resting potential to peak positivity. Its average amplitude is closest to: A. 55 mV | back 15 D. 105 mV |
front 16 During a ventricular action potential, the intracellular potential typically rises from resting level to approximately which peak? A. -65 mV to +10 mV | back 16 B. -85 mV to +20 mV |
front 17 After rapid upstroke, the ventricular cardiac muscle membrane remains depolarized for approximately: A. 0.02 seconds | back 17 C. 0.2 seconds |
front 18 A student asks why ventricular contraction persists much longer in cardiac than skeletal muscle. The best explanation is the cardiac action potential: A. Has no repolarization phase | back 18 C. Includes a plateau phase |
front 19 The action potential of skeletal muscle is caused almost entirely by sudden opening of many: A. L-type calcium channels | back 19 B. Fast sodium channels |
front 20 Fast sodium channels are termed “fast” primarily because they: A. Carry calcium inward rapidly | back 20 D. Open briefly and then close abruptly |
front 21 Cardiac muscle action potentials depend on opening which two channel types? A. Fast sodium and L-type calcium | back 21 A. Fast sodium and L-type calcium |
front 22 Which property best distinguishes the L-type calcium channel? A. Opens faster and closes faster | back 22 B. Opens slower and remains open longer |
front 23 A drug selectively reduces current through calcium-sodium channels in ventricular muscle. Which immediate action-potential change is most expected? A. Faster phase 0 upstroke | back 23 C. Loss of prolonged plateau |
front 24 Compared with skeletal muscle, which membrane property of cardiac muscle most helps explain the prolonged action potential plateau? A. Increased chloride permeability | back 24 D. Fivefold potassium permeability decrease |
front 25 During intracardiac mapping, conduction through ordinary atrial and ventricular muscle fibers is closest to: A. 0.3 to 0.5 m/sec | back 25 A. 0.3 to 0.5 m/sec |
front 26 Which conduction velocity best matches Purkinje fibers? A. 0.05 m/sec | back 26 C. 4 m/sec |
front 27 Which refractory timing pair is normal for cardiac muscle? A. Absolute 0.05; relative 0.3 | back 27 B. Absolute 0.25-0.3; relative 0.05 |
front 28 Compared with ventricles, the refractory period of atrial muscle is: A. Much shorter | back 28 A. Much shorter |
front 29 A physiology professor defines excitation-contraction coupling. Which statement is correct? A. Electrical isolation of atria | back 29 D. AP triggering myofibril contraction |
front 30 In cardiac muscle, an action potential traveling down a T-tubule directly acts on the: A. Fibrous annulus | back 30 B. Sarcoplasmic tubules |
front 31 The immediate result of T-tubule activation of the sarcoplasmic tubules is: A. Sodium release into sarcoplasm | back 31 C. Calcium release into sarcoplasm |
front 32 A key distinction from skeletal muscle is that cardiac myocyte calcium for contraction comes: A. From T-tubules and mitochondria | back 32 C. From T-tubules and SR |
front 33 Calcium entering the cardiac cell through membrane channels next activates which SR structure? A. Ryanodine receptor channels | back 33 A. Ryanodine receptor channels |
front 34 Once present in the sarcoplasm, calcium most directly binds: A. Titin | back 34 D. Troponin |
front 35 Calcium binding to troponin initiates: A. Sodium extrusion from cell and contraction | back 35 B. Cross-bridge formation, contraction |
front 36 Histology shows mucopolysaccharide-rich regions important in calcium handling. These are found in: A. Z lines | back 36 C. T-tubules |
front 37 The major functional role of these mucopolysaccharides is to: A. Buffer intracellular sodium | back 37 B. Store abundant calcium ions |
front 38 In cardiac muscle, the strength of contraction depends strongly on: A. ECF calcium concentration | back 38 A. ECF calcium concentration |
front 39 A perfused heart is placed into a calcium-free solution. It will eventually stop: A. Relaxing | back 39 D. Beating |
front 40 The amount of calcium available in the T-tubule system depends mainly on: A. Plasma glucose concentration | back 40 B. ECF calcium concentration |
front 41 Moderate changes in extracellular calcium concentration have little effect on the force of: A. Skeletal muscle contraction | back 41 A. Skeletal muscle contraction |
front 42 Return of calcium from sarcoplasm back into SR is mediated chiefly by the: A. Sodium-potassium ATPase | back 42 C. Calcium-ATPase pump |
front 43 Calcium is removed from the cardiac cell across the membrane primarily by the: A. L-type calcium channel | back 43 B. Sodium-calcium exchanger |
front 44 All mechanical and electrical events occurring from one heartbeat to the next make up the: A. Cardiac rhythm | back 44 D. Cardiac cycle |
front 45 Each normal cardiac cycle is initiated by the: A. AV node | back 45 B. Sinus node |
front 46 The sinus node is located in the: A. Inferior medial left atrium | back 46 B. Superior lateral right atrium |
front 47 The normal conduction delay between atria and ventricles is approximately: A. 1 second | back 47 C. 0.1 second |
front 48 This atrioventricular delay allows the: A. Atria to contract before ventricles | back 48 A. Atria to contract before ventricles |
front 49 Why is atrial contraction before ventricular contraction functionally important? A. Coronary flow rises before systole | back 49 D. Blood enters ventricles before systole |
front 50 The period of cardiac relaxation is called: A. Diastole | back 50 A. Diastole |
front 51 The period of cardiac contraction is called: A. Diastole | back 51 C. Systole |
front 52 A student is asked how to determine total cardiac cycle duration from heart rate alone. It is best described as the: A. Reciprocal of heart rate | back 52 A. Reciprocal of heart rate |
front 53 In a patient with a heart rate of 75/min, total cardiac cycle duration is closest to: A. 1.2 seconds | back 53 B. 0.8 second cardiac cycle duration = 60 seconds/HR |
front 54 In normal electromechanical coupling, the QRS complex begins just before the onset of: A. Ventricular systole | back 54 A. Ventricular systole |
front 55 A normal upright T wave on ECG most directly represents: A. Atrial contraction | back 55 B. Ventricular repolarization |
front 56 In a resting healthy heart, approximately what fraction of ventricular filling occurs before atrial contraction? A. 20% | back 56 D. 80% |
front 57 On the right atrial pressure tracing, the a wave is produced by: A. Atrial contraction | back 57 A. Atrial contraction |
front 58 The c wave of the atrial pressure curve occurs when the ventricles: A. Finish relaxing | back 58 B. Begin to contract |
front 59 The v wave of the atrial pressure curve occurs toward the end of: A. Atrial contraction | back 59 C. Ventricular contraction |
front 60 During ventricular systole, substantial blood accumulates within the: A. Ventricles | back 60 D. Right and left atria |
front 61 The period of rapid ventricular filling normally occupies about the: A. First third of diastole | back 61 A. First third of diastole |
front 62 Which statement best defines isovolumic contraction? A. Ventricles fill without tension rise | back 62 C. Tension rises with little shortening |
front 63 Ventricular ejection is classically divided into: A. Filling and relaxation phases | back 63 B. Rapid and slow ejection |
front 64 During ventricular ejection, the rapid ejection phase accounts for approximately what proportion of the ejected blood? A. 30% | back 64 C. 70% |
front 65 A ventricle ejects 60 mL from an end-diastolic volume of 100 mL. The ejection fraction is: A. 0.3 | back 65 C. 0.6 ef= sv/edv |
front 66 The fraction of end-diastolic volume ejected by the ventricle is called the: A. Cardiac index | back 66 C. Ejection fraction |
front 67 During systole, backflow from ventricles into atria is prevented by the: A. Semilunar valves | back 67 B. AV valves |
front 68 During diastole, backflow from the aorta and pulmonary arteries into the ventricles is prevented by the: A. AV valves | back 68 D. Semilunar valves |
front 69 Papillary muscles contract when the: A. Atria depolarize | back 69 B. Ventricular walls contract |
front 70 The primary role of papillary muscles is to: A. Open AV valves wider | back 70 B. Pull AV leaflets inward |
front 71 Dysfunction of papillary muscles or chordae tendineae can cause: A. Valve leakage | back 71 A. Valve leakage |
front 72 Compared with semilunar valves, AV valve closure is generally: A. Snapping and louder | back 72 B. Softer |
front 73 Compared with AV valves, semilunar valves close with a more: A. Soft closure | back 73 C. Snapping closure |
front 74 Semilunar valves have smaller openings than AV valves, so blood ejection velocity through them is: A. Lower | back 74 D. Greater |
front 75 The valve type exposed to greater mechanical abrasion is the: A. AV valves | back 75 B. Semilunar valves |
front 76 Immediately after aortic valve closure, a brief notch appears on the aortic pressure curve. This is the: A. c wave | back 76 C. Incisura |
front 77 The incisura occurs because of a brief: A. Forward atrial jet | back 77 B. Backward blood flow |
front 78 A clinician hears acute papillary muscle rupture after myocardial infarction. Which complication best matches the normal function lost? A. AV valve prolapse backward | back 78 A. AV valve prolapse backward |
front 79 During early ventricular systole, the first heart sound is produced primarily by closure of the: A. Semilunar valves | back 79 B. AV valves |
front 80 On auscultation, closure of the AV valves typically generates a sound best described as: A. Low-pitched, prolonged vibration | back 80 A. Low-pitched, prolonged vibration |
front 81 At the end of systole, semilunar valve closure is heard as a: A. Low rumbling vibration | back 81 C. Rapid snap, briefly vibrating |
front 82 The amount of energy the heart converts to work during a single heartbeat is called: A. Cardiac output | back 82 B. Stroke work output |
front 83 The total energy converted to work by the heart in 1 minute is the: A. External work | back 83 C. Minute work output |
front 84 Minute work output is equal to: A. Stroke volume × afterload | back 84 B. Stroke work × heart rate |
front 85 External work, or volume-pressure work, is performed when blood is moved from: A. High arteries to low veins | back 85 B. Low veins to high arteries |
front 86 The kinetic energy of blood flow refers most directly to: A. Passive ventricular filling | back 86 D. Acceleration to ejection velocity |
front 87 Right ventricular external work output is normally about what fraction of left ventricular work? A. One half | back 87 B. One sixth |
front 88 The main reason right ventricular external work is far lower than left ventricular work is the: A. Lower right ventricular volume | back 88 C. Sixfold systolic pressure difference |
front 89 The degree of tension on a muscle when it begins to contract is called: A. Afterload | back 89 C. Preload |
front 90 The load against which a muscle exerts contractile force is the: A. Afterload | back 90 A. Afterload |
front 91 For cardiac muscle, preload is usually considered to be the ventricular: A. End-systolic pressure | back 91 B. End-diastolic pressure |
front 92 Myocardial oxygen consumption is a good measure of the: A. Stroke volume reserve | back 92 C. Chemical energy liberated |
front 93 Additional work that could be done if the ventricle emptied all blood with each beat is called: A. Kinetic reserve | back 93 C. Potential energy |
front 94 Cardiac oxygen consumption is most proportional to the: A. Heart rate alone | back 94 C. Tension × time duration |
front 95 The tension-time index measures: A. Pressure plus heart rate | back 95 B. Tension × contraction duration |
front 96 During cardiac contraction, most expended chemical energy is converted into: A. Electrical current | back 96 D. Heat |
front 97 The ratio of work output to total chemical energy expenditure is the: A. Cardiac reserve | back 97 C. Contractile efficiency |
front 98 The volume pumped by the heart is regulated by: A. Valve area and venous tone | back 98 B. Intrinsic control and ANS |
front 99 The intrinsic ability of the heart to adapt to increasing venous inflow is the: A. Bainbridge mechanism | back 99 C. Frank-Starling mechanism |
front 100 As ventricular filling increases, myocardial stretch increases, producing: A. Less force, less output | back 100 B. More force, more output |
front 101 Parasympathetic vagal fibers are distributed mainly in the: A. Ventricles | back 101 D. Atria |
front 102 Excess extracellular potassium classically makes the heart: A. Spastic and tachycardic | back 102 B. Dilated, flaccid, bradycardic |
front 103 Excess extracellular calcium most characteristically causes the heart to undergo: A. Flaccid dilation | back 103 B. Spastic contraction |
front 104 Which measure more directly tracks chemical energy use? A. Tension-time index | back 104 A. Tension-time index |
front 105 Which change most directly increases left ventricular work? A. Lower preload | back 105 C. Higher afterload |
front 106 A patient with isolated right ventricular failure would most directly impair blood flow through the: A. systemic circulation | back 106 C. lungs |
front 107 A patient with severe left ventricular systolic dysfunction will most directly reduce blood flow through the: A. pulmonary circulation | back 107 B. systemic circulation |
front 108 The phrase “cardiac rhythmicity” most directly refers to: A. valve closure sequence | back 108 C. AP transmission causing beats |
front 109 Specialized cardiac tissue is best divided into: A. atrial and ventricular | back 109 B. excitatory and conductive |
front 110 Specialized excitatory and conductive fibers contract feebly because they contain: A. excess intercalated discs | back 110 B. few contractile fibrils |
front 111 Dark transverse bands crossing cardiac muscle fibers are called: A. Z lines | back 111 D. intercalated discs |
front 112 At each intercalated disc, cell membranes form permeable: A. occluding junctions | back 112 C. communicating junctions |
front 113 These communicating junctions are important because they allow rapid diffusion of: A. proteins | back 113 B. ions |
front 114 Cardiac muscle is called a syncytium because excitation in one cell rapidly: A. stops at fibrous rings | back 114 B. spreads to neighboring cells |
front 115 The two major syncytia of the heart are the: A. right and left | back 115 B. atrial and ventricular |
front 116 Potentials are normally not directly conducted from atrial to ventricular syncytium through the intervening: A. fatty tissue | back 116 B. fibrous tissue |
front 117 The classic fast-response action potential averaging about 105 mV is recorded in: A. SA nodal tissue | back 117 C. ventricular muscle |
front 118 A student asks why cardiac muscle, but not skeletal muscle, has a plateau phase. The best answer is that cardiac muscle uses: A. chloride and potassium channels | back 118 D. sodium and L-type calcium |
front 119 Skeletal muscle action potentials depend primarily on: A. slow calcium influx | back 119 B. fast sodium channels |
front 120 Immediately after cardiac action potential onset, membrane permeability to potassium: A. rises fivefold | back 120 C. decreases about fivefold |
front 121 During phase 0 of the cardiac muscle action potential, the main event is opening of: A. slow potassium channels | back 121 C. fast sodium channels |
front 122 During phase 1, the fast sodium channels: A. remain open | back 122 B. close |
front 123 During phase 1, which ion also leaves the cell? A. calcium | back 123 D. potassium |
front 124 During phase 2, the plateau phase is produced when: A. calcium opens, fast potassium closes | back 124 A. calcium opens, fast potassium closes |
front 125 During phase 3 rapid repolarization, calcium channels close and which channels open? A. fast sodium | back 125 C. slow potassium |
front 126 The resting membrane potential in phase 4 is closest to: A. -60 mV | back 126 C. -90 mV |
front 127 The conduction velocity in Purkinje fibers may reach: A. 0.3 m/sec | back 127 D. 4 m/sec |
front 128 The main physiologic importance of rapid Purkinje conduction is: A. slower atrial filling | back 128 B. rapid ventricular activation |
front 129 A histology stain highlights negatively charged material within cardiac T tubules that binds calcium. This material is: A. phospholipids | back 129 B. mucopolysaccharides |
front 130 The major functional importance of mucopolysaccharides in cardiac T tubules is that they: A. store abundant calcium ions | back 130 A. store abundant calcium ions |
front 131 More than 0.1 second normally elapses during conduction from atria to ventricles. This interval reflects the: A. SA nodal recovery time | back 131 B. atrioventricular conduction delay |
front 132 The minor elevations of the atrial pressure curve are termed the: A. x, y, z waves | back 132 C. a, c, v waves |
front 133 During ventricular systole, blood accumulates in both atria primarily because the: A. semilunar valves are open | back 133 B. AV valves are closed |
front 134 The tricuspid and mitral valves are classified as: A. semilunar valves | back 134 B. AV valves |
front 135 The aortic and pulmonary valves are examples of: A. semilunar valves | back 135 A. semilunar valves |
front 136 Papillary muscles attach to the leaflets of the AV valves by the: A. trabeculae carneae | back 136 C. chordae tendineae |
front 137 Which valve type is supported by chordae tendineae? A. aortic valves | back 137 C. AV valves |
front 138 The second heart sound is produced when the: A. AV valves close slowly | back 138 C. semilunar valves close rapidly |
front 139 Why is the second heart sound relatively short in duration? A. atrial contraction is brief | back 139 D. surrounding tissues vibrate briefly |
front 140 Movement of blood from low-pressure veins to high-pressure arteries is termed: A. kinetic reserve work | back 140 B. external volume-pressure work |
front 141 A hemodynamics lecturer uses “external work” and “volume-pressure work” interchangeably. This work refers to: A. valve closure energy | back 141 C. venous-to-arterial blood movement |
front 142 In a healthy adult, the normal left ventricle can generate a maximum systolic pressure closest to: A. 250-300 mm Hg | back 142 A. 250-300 mm Hg |
front 143 During invasive hemodynamic testing, the normal right ventricle can generate a maximum systolic pressure closest to: A. 20-30 mm Hg | back 143 D. 60-80 mm Hg |
front 144 Which sequence correctly lists the major phases of the cardiac cycle? A. filling, ejection, relaxation, contraction | back 144 B. filling, isovolumic contraction, ejection, relaxation |
front 145 For the ventricle, preload is usually considered to be the end-diastolic pressure when the chamber has become: A. emptied | back 145 D. filled |
front 146 For the left ventricle, afterload is best approximated by the pressure in the: A. pulmonary artery | back 146 B. aorta |
front 147 Maximum efficiency of the normal heart is usually: A. 5-10 percent | back 147 B. 20-25 percent |
front 148 In severe heart failure, cardiac efficiency may fall to: A. 15-20 percent | back 148 D. 5-10 percent |
front 149 A patient receives a large saline bolus. If intrinsic cardiac regulation is intact, the immediate rise in ventricular filling should produce: A. weaker contraction, less output | back 149 C. stronger contraction, more output |
front 150 A ventricle must generate enough force to overcome pressure in the vessel leaving it. For the left ventricle, that vessel is the: A. pulmonary artery | back 150 C. aorta |