Which phrase best describes the normal mechanical role of the atria?

A. Strong afterload generators
B. Weak primer pumps
C. Passive resistance chambers
D. Major ejection reservoirs

B. Weak primer pumps

A congenital lesion selectively impairs right ventricular outflow. Which circulation is most directly underfilled?

A. Coronary circulation
B. Systemic circulation
C. Pulmonary circulation
D. Cerebral circulation

C. Pulmonary circulation

A patient in sinus rhythm has repeated, orderly heart contractions occurring without interruption. This ongoing sequence is best termed:

A. Cardiac rhythmicity
B. Mechanical lusitropy
C. Ventricular compliance
D. Myocardial refractoriness

A. Cardiac rhythmicity

A physiology lab asks which grouping correctly lists the three major types of heart muscle. Which is correct?

A. Atrial, Purkinje, papillary
B. Ventricular, nodal, septal
C. Atrial, ventricular, conductive
D. Smooth, skeletal, conductive

C. Atrial, ventricular, conductive

Compared with skeletal muscle, cardiac muscle contraction is most similar except for which feature being longer?

A. Sarcomere width
B. Duration
C. Threshold voltage
D. Resting resistance

B. Duration

On microscopy, a student identifies the usual contractile myofibrillar elements of cardiac muscle. These are:

A. Troponin and tropomyosin
B. Dynein and kinesin
C. Actin and myosin filaments
D. Desmin and titin

C. Actin and myosin filaments

Intercalated discs are best described as:

A. Extracellular collagen partitions
B. Cell membranes between myocytes
C. Sarcoplasmic reticulum expansions
D. Intracellular glycogen bands

B. Cell membranes between myocytes

At the intercalated disc, adjacent cardiac cell membranes join to form structures that permit ionic current spread. These are:

A. Tight occluding junctions
B. Impermeable desmosomal plates
C. Permeable communicating junctions
D. Sodium leak channel clusters

C. Permeable communicating junctions

A toxic exposure disrupts gap junction function throughout the myocardium. Which immediate effect is most expected?

A. Slower action potential spread
B. Stronger skeletal-like contraction
C. Lower myosin production
D. Faster valve opening

A. Slower action potential spread

In a normal heart, the myocardium is functionally arranged into two major syncytia. These are:

A. Endocardial and epicardial
B. Right and left
C. Basal and apical
D. Atrial and ventricular

D. Atrial and ventricular

During dissection, a fibrous plane is identified encircling the atrioventricular valvular openings. This tissue normally separates the:

A. Great arteries from atria
B. Ventricles from pericardium
C. Atria from ventricles
D. Conduction fibers from valves

C. Atria from ventricles

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
B. Fibrous tissue
C. Skeletal muscle cuffs
D. Elastic lamellar sheets

B. Fibrous tissue

The normal separation of atrial and ventricular syncytia provides which mechanical advantage?

A. Simultaneous chamber ejection
B. Ventricles fill after atria contract
C. Atria relax after systole
D. Semilunar valves open earlier

B. Ventricles fill after atria contract

When a standard fast-response cardiac action potential is recorded for teaching purposes, it is classically taken from a:

A. Ventricular muscle fiber
B. SA nodal cell
C. Atrial septal fibroblast
D. AV nodal cell

A. Ventricular muscle fiber

A ventricular myocyte action potential is measured from resting potential to peak positivity. Its average amplitude is closest to:

A. 55 mV
B. 75 mV
C. 90 mV
D. 105 mV

D. 105 mV

During a ventricular action potential, the intracellular potential typically rises from resting level to approximately which peak?

A. -65 mV to +10 mV
B. -85 mV to +20 mV
C. -90 mV to +35 mV
D. -70 mV to 0 mV

B. -85 mV to +20 mV

After rapid upstroke, the ventricular cardiac muscle membrane remains depolarized for approximately:

A. 0.02 seconds
B. 2 seconds
C. 0.2 seconds
D. 0.002 seconds

C. 0.2 seconds

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
B. Lacks sodium channel activation
C. Includes a plateau phase
D. Begins from a positive baseline

C. Includes a plateau phase

The action potential of skeletal muscle is caused almost entirely by sudden opening of many:

A. L-type calcium channels
B. Fast sodium channels
C. Potassium rectifier channels
D. Chloride conductance channels

B. Fast sodium channels

Fast sodium channels are termed “fast” primarily because they:

A. Carry calcium inward rapidly
B. Open only during diastole
C. Inactivate after several seconds
D. Open briefly and then close abruptly

D. Open briefly and then close abruptly

Cardiac muscle action potentials depend on opening which two channel types?

A. Fast sodium and L-type calcium
B. T-type calcium and chloride
C. Potassium and funny channels
D. Sodium-potassium cotransporters only

A. Fast sodium and L-type calcium

Which property best distinguishes the L-type calcium channel?

A. Opens faster and closes faster
B. Opens slower and remains open longer
C. Inactivates at lower voltages
D. Conducts only sodium inward

B. Opens slower and remains open longer

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
B. Shorter skeletal twitch only
C. Loss of prolonged plateau
D. Earlier atrial depolarization

C. Loss of prolonged plateau

Compared with skeletal muscle, which membrane property of cardiac muscle most helps explain the prolonged action potential plateau?

A. Increased chloride permeability
B. Reduced sodium channel density
C. Greater resting calcium leak
D. Fivefold potassium permeability decrease

D. Fivefold potassium permeability decrease

During intracardiac mapping, conduction through ordinary atrial and ventricular muscle fibers is closest to:

A. 0.3 to 0.5 m/sec
B. 1 to 2 m/sec
C. 2 to 3 m/sec
D. 4 to 5 m/sec

A. 0.3 to 0.5 m/sec

Which conduction velocity best matches Purkinje fibers?

A. 0.05 m/sec
B. 0.5 m/sec
C. 4 m/sec
D. 8 m/sec

C. 4 m/sec

Which refractory timing pair is normal for cardiac muscle?

A. Absolute 0.05; relative 0.3
B. Absolute 0.25-0.3; relative 0.05
C. Absolute 0.1; relative 0.2
D. Absolute 0.4; relative 0.1

B. Absolute 0.25-0.3; relative 0.05

Compared with ventricles, the refractory period of atrial muscle is:

A. Much shorter
B. Slightly longer
C. Nearly identical
D. More calcium-dependent

A. Much shorter

A physiology professor defines excitation-contraction coupling. Which statement is correct?

A. Electrical isolation of atria
B. Refractory recovery after systole
C. Purkinje conduction to papillary muscle
D. AP triggering myofibril contraction

D. AP triggering myofibril contraction

In cardiac muscle, an action potential traveling down a T-tubule directly acts on the:

A. Fibrous annulus
B. Sarcoplasmic tubules
C. Intercalated discs
D. Purkinje membrane

B. Sarcoplasmic tubules

The immediate result of T-tubule activation of the sarcoplasmic tubules is:

A. Sodium release into sarcoplasm
B. Potassium uptake into SR
C. Calcium release into sarcoplasm
D. Troponin movement into T-tubules

C. Calcium release into sarcoplasm

A key distinction from skeletal muscle is that cardiac myocyte calcium for contraction comes:

A. From T-tubules and mitochondria
B. Primarily from SR stores
C. From T-tubules and SR
D. From extracellular sodium exchange

C. From T-tubules and SR

Calcium entering the cardiac cell through membrane channels next activates which SR structure?

A. Ryanodine receptor channels
B. Calcium-ATPase pumps
C. Fast sodium channels
D. Potassium leak channels

A. Ryanodine receptor channels

Once present in the sarcoplasm, calcium most directly binds:

A. Titin
B. Desmin
C. Tropomyosin
D. Troponin

D. Troponin

Calcium binding to troponin initiates:

A. Sodium extrusion from cell and contraction
B. Cross-bridge formation and contraction
C. Gap junction opening and contraction
D. SR calcium reuptake and contraction

B. Cross-bridge formation, contraction

Histology shows mucopolysaccharide-rich regions important in calcium handling. These are found in:

A. Z lines
B. AV node
C. T-tubules
D. Intercalated discs

C. T-tubules

The major functional role of these mucopolysaccharides is to:

A. Buffer intracellular sodium
B. Store abundant calcium ions
C. Accelerate potassium efflux
D. Stabilize actin filaments

B. Store abundant calcium ions

In cardiac muscle, the strength of contraction depends strongly on:

A. ECF calcium concentration
B. Intracellular chloride levels
C. Resting membrane sodium
D. Myosin ATPase subtype

A. ECF calcium concentration

A perfused heart is placed into a calcium-free solution. It will eventually stop:

A. Relaxing
B. Conducting
C. Filling
D. Beating

D. Beating

The amount of calcium available in the T-tubule system depends mainly on:

A. Plasma glucose concentration
B. ECF calcium concentration
C. SR potassium content
D. Intracellular ATP stores

B. ECF calcium concentration

Moderate changes in extracellular calcium concentration have little effect on the force of:

A. Skeletal muscle contraction
B. Purkinje fiber conduction
C. Cardiac atrial contraction
D. AV nodal depolarization

A. Skeletal muscle contraction

Return of calcium from sarcoplasm back into SR is mediated chiefly by the:

A. Sodium-potassium ATPase
B. Ryanodine receptor
C. Calcium-ATPase pump
D. Fast sodium channel

C. Calcium-ATPase pump

Calcium is removed from the cardiac cell across the membrane primarily by the:

A. L-type calcium channel
B. Sodium-calcium exchanger
C. Ryanodine receptor
D. Funny current channel

B. Sodium-calcium exchanger

All mechanical and electrical events occurring from one heartbeat to the next make up the:

A. Cardiac rhythm
B. Ventricular filling phase
C. Absolute refractory period
D. Cardiac cycle

D. Cardiac cycle

Each normal cardiac cycle is initiated by the:

A. AV node
B. Sinus node
C. Purkinje fibers
D. Ventricular septum

B. Sinus node

The sinus node is located in the:

A. Inferior medial left atrium
B. Superior lateral right atrium
C. Posterior interventricular septum
D. Coronary sinus floor

B. Superior lateral right atrium

The normal conduction delay between atria and ventricles is approximately:

A. 1 second
B. 0.2 second
C. 0.1 second
D. 0.01 second

C. 0.1 second

This atrioventricular delay allows the:

A. Atria to contract before ventricles
B. Ventricles to contract before atria
C. Semilunar valves to open early
D. Purkinje fibers to repolarize first

A. Atria to contract before ventricles

Why is atrial contraction before ventricular contraction functionally important?

A. Coronary flow rises before systole
B. AV valves open during ejection
C. Aortic pressure falls before filling
D. Blood enters ventricles before systole

D. Blood enters ventricles before systole

The period of cardiac relaxation is called:

A. Diastole
B. Systole
C. Afterload
D. Ejection

A. Diastole

The period of cardiac contraction is called:

A. Diastole
B. Lusitropy
C. Systole
D. Refractoriness

C. Systole

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
B. Product of stroke volume
C. Sum of systole only
D. Fraction of end-systole

A. Reciprocal of heart rate

In a patient with a heart rate of 75/min, total cardiac cycle duration is closest to:

A. 1.2 seconds
B. 0.8 second
C. 0.5 second
D. 0.2 second

B. 0.8 second

cardiac cycle duration = 60 seconds/HR

In normal electromechanical coupling, the QRS complex begins just before the onset of:

A. Ventricular systole
B. Atrial systole
C. Ventricular repolarization
D. Semilunar closure

A. Ventricular systole

A normal upright T wave on ECG most directly represents:

A. Atrial contraction
B. Ventricular repolarization
C. Ventricular depolarization
D. AV nodal delay

B. Ventricular repolarization

In a resting healthy heart, approximately what fraction of ventricular filling occurs before atrial contraction?

A. 20%
B. 40%
C. 60%
D. 80%

D. 80%

On the right atrial pressure tracing, the a wave is produced by:

A. Atrial contraction
B. Venous filling only
C. AV valve opening
D. Ventricular ejection

A. Atrial contraction

The c wave of the atrial pressure curve occurs when the ventricles:

A. Finish relaxing
B. Begin to contract
C. Finish ejecting
D. Begin repolarizing

B. Begin to contract

The v wave of the atrial pressure curve occurs toward the end of:

A. Atrial contraction
B. Isovolumic relaxation
C. Ventricular contraction
D. Rapid ventricular filling

C. Ventricular contraction

During ventricular systole, substantial blood accumulates within the:

A. Ventricles
B. Great arteries
C. Coronary sinuses
D. Right and left atria

D. Right and left atria

The period of rapid ventricular filling normally occupies about the:

A. First third of diastole
B. Last third of systole
C. Middle half of systole
D. Final tenth of diastole

A. First third of diastole

Which statement best defines isovolumic contraction?

A. Ventricles fill without tension rise
B. Fibers shorten without pressure rise
C. Tension rises with little shortening
D. Ejection occurs with valve opening

C. Tension rises with little shortening

Ventricular ejection is classically divided into:

A. Filling and relaxation phases
B. Rapid and slow ejection
C. Atrial and ventricular phases
D. Pressure and volume waves

B. Rapid and slow ejection

During ventricular ejection, the rapid ejection phase accounts for approximately what proportion of the ejected blood?

A. 30%
B. 50%
C. 70%
D. 90%

C. 70%

A ventricle ejects 60 mL from an end-diastolic volume of 100 mL. The ejection fraction is:

A. 0.3
B. 0.4
C. 0.6
D. 0.8

C. 0.6

ef= sv/edv

The fraction of end-diastolic volume ejected by the ventricle is called the:

A. Cardiac index
B. Stroke work
C. Ejection fraction
D. End-systolic reserve

C. Ejection fraction

During systole, backflow from ventricles into atria is prevented by the:

A. Semilunar valves
B. AV valves
C. Coronary ostia
D. Eustachian valves

B. AV valves

During diastole, backflow from the aorta and pulmonary arteries into the ventricles is prevented by the:

A. AV valves
B. Papillary muscles
C. Chordae tendineae
D. Semilunar valves

D. Semilunar valves

Papillary muscles contract when the:

A. Atria depolarize
B. Ventricular walls contract
C. Semilunar valves open
D. AV node fires

B. Ventricular walls contract

The primary role of papillary muscles is to:

A. Open AV valves wider
B. Pull AV leaflets inward
C. Close semilunar cusps
D. Shorten ventricular systole

B. Pull AV leaflets inward

Dysfunction of papillary muscles or chordae tendineae can cause:

A. Valve leakage
B. Sinus bradycardia
C. Aortic stenosis
D. Atrial standstill

A. Valve leakage

Compared with semilunar valves, AV valve closure is generally:

A. Snapping and louder
B. Softer
C. Delayed by T wave
D. Linked to incisura

B. Softer

Compared with AV valves, semilunar valves close with a more:

A. Soft closure
B. Fused motion
C. Snapping closure
D. Silent recoil

C. Snapping closure

Semilunar valves have smaller openings than AV valves, so blood ejection velocity through them is:

A. Lower
B. Variable
C. Unchanged
D. Greater

D. Greater

The valve type exposed to greater mechanical abrasion is the:

A. AV valves
B. Semilunar valves
C. Mitral valve
D. Tricuspid valve

B. Semilunar valves

Immediately after aortic valve closure, a brief notch appears on the aortic pressure curve. This is the:

A. c wave
B. Dicrotic plateau
C. Incisura
D. v descent

C. Incisura

The incisura occurs because of a brief:

A. Forward atrial jet
B. Backward blood flow
C. Papillary contraction
D. Ventricular filling surge

B. Backward blood flow

A clinician hears acute papillary muscle rupture after myocardial infarction. Which complication best matches the normal function lost?

A. AV valve prolapse backward
B. Semilunar valve calcification
C. Delayed SA node firing
D. Reduced atrial depolarization

A. AV valve prolapse backward

During early ventricular systole, the first heart sound is produced primarily by closure of the:

A. Semilunar valves
B. AV valves
C. Pulmonary veins
D. Venae cavae

B. AV valves

On auscultation, closure of the AV valves typically generates a sound best described as:

A. Low-pitched, prolonged vibration
B. High-pitched, brief snap
C. Silent, pressure-only event
D. Musical midsystolic click

A. Low-pitched, prolonged vibration

At the end of systole, semilunar valve closure is heard as a:

A. Low rumbling vibration
B. Long harsh murmur
C. Rapid snap, briefly vibrating
D. Sustained opening click

C. Rapid snap, briefly vibrating

The amount of energy the heart converts to work during a single heartbeat is called:

A. Cardiac output
B. Stroke work output
C. Minute work output
D. Tension-time index

B. Stroke work output

The total energy converted to work by the heart in 1 minute is the:

A. External work
B. Potential energy
C. Minute work output
D. Kinetic pressure load

C. Minute work output

Minute work output is equal to:

A. Stroke volume × afterload
B. Stroke work × heart rate
C. Oxygen use × preload
D. Cardiac output × preload

B. Stroke work × heart rate

External work, or volume-pressure work, is performed when blood is moved from:

A. High arteries to low veins
B. Low veins to high arteries
C. Atria to coronary sinuses
D. Pulmonary veins to venae cavae

B. Low veins to high arteries

The kinetic energy of blood flow refers most directly to:

A. Passive ventricular filling
B. Valve leaflet recoil
C. Myocardial heat generation
D. Acceleration to ejection velocity

D. Acceleration to ejection velocity

Right ventricular external work output is normally about what fraction of left ventricular work?

A. One half
B. One sixth
C. One third
D. One tenth

B. One sixth

The main reason right ventricular external work is far lower than left ventricular work is the:

A. Lower right ventricular volume
B. Shorter right ventricular systole
C. Sixfold systolic pressure difference
D. Smaller tricuspid valve area

C. Sixfold systolic pressure difference

The degree of tension on a muscle when it begins to contract is called:

A. Afterload
B. Contractility
C. Preload
D. Compliance

C. Preload

The load against which a muscle exerts contractile force is the:

A. Afterload
B. Preload
C. Stroke work
D. Efficiency

A. Afterload

For cardiac muscle, preload is usually considered to be the ventricular:

A. End-systolic pressure
B. End-diastolic pressure
C. Mean arterial pressure
D. Pulse pressure

B. End-diastolic pressure

Myocardial oxygen consumption is a good measure of the:

A. Stroke volume reserve
B. Valvular pressure gradient
C. Chemical energy liberated
D. Ventricular filling fraction

C. Chemical energy liberated

Additional work that could be done if the ventricle emptied all blood with each beat is called:

A. Kinetic reserve
B. Volume-pressure work
C. Potential energy
D. Residual afterload

C. Potential energy

Cardiac oxygen consumption is most proportional to the:

A. Heart rate alone
B. Pressure-volume area
C. Tension × time duration
D. Stroke volume × pulse pressure

C. Tension × time duration

The tension-time index measures:

A. Pressure plus heart rate
B. Tension × contraction duration
C. Volume × ejection velocity
D. Preload minus afterload

B. Tension × contraction duration

During cardiac contraction, most expended chemical energy is converted into:

A. Electrical current
B. External work
C. Kinetic energy
D. Heat

D. Heat

The ratio of work output to total chemical energy expenditure is the:

A. Cardiac reserve
B. Ejection fraction
C. Contractile efficiency
D. Tension-time index

C. Contractile efficiency

The volume pumped by the heart is regulated by:

A. Valve area and venous tone
B. Intrinsic control and ANS
C. Coronary flow alone
D. Papillary muscle tension

B. Intrinsic control and ANS

The intrinsic ability of the heart to adapt to increasing venous inflow is the:

A. Bainbridge mechanism
B. Hering-Breuer reflex
C. Frank-Starling mechanism
D. Baroreceptor reflex

C. Frank-Starling mechanism

As ventricular filling increases, myocardial stretch increases, producing:

A. Less force, less output
B. More force, more output
C. Less force, more output
D. More force, less output

B. More force, more output

Parasympathetic vagal fibers are distributed mainly in the:

A. Ventricles
B. Purkinje system
C. Interventricular septum
D. Atria

D. Atria

Excess extracellular potassium classically makes the heart:

A. Spastic and tachycardic
B. Dilated, flaccid, bradycardic
C. Hypercontractile and narrowed
D. Small, rigid, tachycardic

B. Dilated, flaccid, bradycardic

Excess extracellular calcium most characteristically causes the heart to undergo:

A. Flaccid dilation
B. Spastic contraction
C. Electrical standstill
D. Marked valve insufficiency

B. Spastic contraction

Which measure more directly tracks chemical energy use?

A. Tension-time index
B. Ejection fraction
C. Valve closing pressure
D. End-systolic volume

A. Tension-time index

Which change most directly increases left ventricular work?

A. Lower preload
B. Lower vagal tone
C. Higher afterload
D. Shorter systole

C. Higher afterload

A patient with isolated right ventricular failure would most directly impair blood flow through the:

A. systemic circulation
B. coronary circulation
C. lungs
D. cerebral circulation

C. lungs

A patient with severe left ventricular systolic dysfunction will most directly reduce blood flow through the:

A. pulmonary circulation
B. systemic circulation
C. coronary sinus
D. right atrium

B. systemic circulation

The phrase “cardiac rhythmicity” most directly refers to:

A. valve closure sequence
B. coronary artery filling
C. AP transmission causing beats
D. papillary muscle shortening

C. AP transmission causing beats

Specialized cardiac tissue is best divided into:

A. atrial and ventricular
B. excitatory and conductive
C. nodal and papillary
D. automatic and contractile

B. excitatory and conductive

Specialized excitatory and conductive fibers contract feebly because they contain:

A. excess intercalated discs
B. few contractile fibrils
C. low resting potassium
D. reduced membrane calcium

B. few contractile fibrils

Dark transverse bands crossing cardiac muscle fibers are called:

A. Z lines
B. T tubules
C. sarcoplasmic discs
D. intercalated discs

D. intercalated discs

At each intercalated disc, cell membranes form permeable:

A. occluding junctions
B. insulating septa
C. communicating junctions
D. desmin bridges

C. communicating junctions

These communicating junctions are important because they allow rapid diffusion of:

A. proteins
B. ions
C. glycogen
D. ATP

B. ions

Cardiac muscle is called a syncytium because excitation in one cell rapidly:

A. stops at fibrous rings
B. spreads to neighboring cells
C. enters coronary vessels
D. depolarizes connective tissue

B. spreads to neighboring cells

The two major syncytia of the heart are the:

A. right and left
B. atrial and ventricular
C. basal and apical
D. septal and free-wall

B. atrial and ventricular

Potentials are normally not directly conducted from atrial to ventricular syncytium through the intervening:

A. fatty tissue
B. fibrous tissue
C. Purkinje tissue
D. nodal tissue

B. fibrous tissue

The classic fast-response action potential averaging about 105 mV is recorded in:

A. SA nodal tissue
B. atrial pacemaker cells
C. ventricular muscle
D. papillary fibroblasts

C. ventricular muscle

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
B. sodium and funny channels
C. sodium channels only
D. sodium and L-type calcium

D. sodium and L-type calcium

Skeletal muscle action potentials depend primarily on:

A. slow calcium influx
B. fast sodium channels
C. potassium channel closure
D. sodium-calcium exchange

B. fast sodium channels

Immediately after cardiac action potential onset, membrane permeability to potassium:

A. rises fivefold
B. disappears completely
C. decreases about fivefold
D. remains unchanged

C. decreases about fivefold

During phase 0 of the cardiac muscle action potential, the main event is opening of:

A. slow potassium channels
B. L-type calcium channels
C. fast sodium channels
D. chloride channels

C. fast sodium channels

During phase 1, the fast sodium channels:

A. remain open
B. close
C. reactivate fully
D. become calcium selective

B. close

During phase 1, which ion also leaves the cell?

A. calcium
B. chloride
C. sodium
D. potassium

D. potassium

During phase 2, the plateau phase is produced when:

A. calcium opens, fast potassium closes
B. sodium opens, chloride closes
C. slow potassium opens, calcium closes
D. sodium closes, calcium closes

A. calcium opens, fast potassium closes

During phase 3 rapid repolarization, calcium channels close and which channels open?

A. fast sodium
B. funny sodium
C. slow potassium
D. chloride leak

C. slow potassium

The resting membrane potential in phase 4 is closest to:

A. -60 mV
B. -75 mV
C. -90 mV
D. +20 mV

C. -90 mV

The conduction velocity in Purkinje fibers may reach:

A. 0.3 m/sec
B. 1 m/sec
C. 2 m/sec
D. 4 m/sec

D. 4 m/sec

The main physiologic importance of rapid Purkinje conduction is:

A. slower atrial filling
B. rapid ventricular activation
C. delayed valve closure
D. reduced coronary flow

B. rapid ventricular activation

A histology stain highlights negatively charged material within cardiac T tubules that binds calcium. This material is:

A. phospholipids
B. mucopolysaccharides
C. troponins
D. desmosomes

B. mucopolysaccharides

The major functional importance of mucopolysaccharides in cardiac T tubules is that they:

A. store abundant calcium ions
B. accelerate sodium influx
C. inhibit potassium efflux
D. open ryanodine channels

A. store abundant calcium ions

More than 0.1 second normally elapses during conduction from atria to ventricles. This interval reflects the:

A. SA nodal recovery time
B. atrioventricular conduction delay
C. ventricular refractory period
D. semilunar valve opening time

B. atrioventricular conduction delay

The minor elevations of the atrial pressure curve are termed the:

A. x, y, z waves
B. p, q, r waves
C. a, c, v waves
D. s, t, u waves

C. a, c, v waves

During ventricular systole, blood accumulates in both atria primarily because the:

A. semilunar valves are open
B. AV valves are closed
C. atria stop receiving venous return
D. ventricles become highly compliant

B. AV valves are closed

The tricuspid and mitral valves are classified as:

A. semilunar valves
B. AV valves
C. outflow valves
D. arterial valves

B. AV valves

The aortic and pulmonary valves are examples of:

A. semilunar valves
B. AV valves
C. venous valves
D. inflow valves

A. semilunar valves

Papillary muscles attach to the leaflets of the AV valves by the:

A. trabeculae carneae
B. annulus fibrosus
C. chordae tendineae
D. moderator bands

C. chordae tendineae

Which valve type is supported by chordae tendineae?

A. aortic valves
B. semilunar valves
C. AV valves
D. pulmonary valves

C. AV valves

The second heart sound is produced when the:

A. AV valves close slowly
B. ventricles begin filling
C. semilunar valves close rapidly
D. papillary muscles relax suddenly

C. semilunar valves close rapidly

Why is the second heart sound relatively short in duration?

A. atrial contraction is brief
B. valves close before systole
C. ventricular filling is passive
D. surrounding tissues vibrate briefly

D. surrounding tissues vibrate briefly

Movement of blood from low-pressure veins to high-pressure arteries is termed:

A. kinetic reserve work
B. external volume-pressure work
C. potential pressure loading
D. contractile efficiency work

B. external volume-pressure work

A hemodynamics lecturer uses “external work” and “volume-pressure work” interchangeably. This work refers to:

A. valve closure energy
B. blood acceleration alone
C. venous-to-arterial blood movement
D. papillary muscle shortening

C. venous-to-arterial blood movement

In a healthy adult, the normal left ventricle can generate a maximum systolic pressure closest to:

A. 250-300 mm Hg
B. 100-120 mm Hg
C. 60-80 mm Hg
D. 150-180 mm Hg

A. 250-300 mm Hg

During invasive hemodynamic testing, the normal right ventricle can generate a maximum systolic pressure closest to:

A. 20-30 mm Hg
B. 100-120 mm Hg
C. 250-300 mm Hg
D. 60-80 mm Hg

D. 60-80 mm Hg

Which sequence correctly lists the major phases of the cardiac cycle?

A. filling, ejection, relaxation, contraction
B. filling, isovolumic contraction, ejection, relaxation
C. filling, atrial systole, ejection, dilation
D. contraction, filling, ejection, recovery

B. filling, isovolumic contraction, ejection, relaxation

For the ventricle, preload is usually considered to be the end-diastolic pressure when the chamber has become:

A. emptied
B. stretched maximally
C. afterloaded
D. filled

D. filled

For the left ventricle, afterload is best approximated by the pressure in the:

A. pulmonary artery
B. aorta
C. left atrium
D. vena cava

B. aorta

Maximum efficiency of the normal heart is usually:

A. 5-10 percent
B. 20-25 percent
C. 35-40 percent
D. 50-60 percent

B. 20-25 percent

In severe heart failure, cardiac efficiency may fall to:

A. 15-20 percent
B. 20-25 percent
C. 30-35 percent
D. 5-10 percent

D. 5-10 percent

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
B. no change in force
C. stronger contraction, more output
D. slower rate, less output

C. stronger contraction, more output

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
B. left atrium
C. aorta
D. superior vena cava

C. aorta