Phys 9 Flashcards

Which option best characterizes the physiological function of the atria in the cardiac cycle?

A. High-pressure afterload generators

B. Primer pumps for ventricular filling

C. High-resistance capacitance chambers

D. Primary ejection reservoirs

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

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 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

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

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

Intercalated discs are best described as:

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

Which structures at the intercalated disc allow for rapid ionic current spread and electrical coupling between adjacent cardiomyocytes?

A. Tight (occluding) junctions

B. Desmosomes (maculae adherentes)

C. Gap (communicating) junctions

D. Voltage-gated sodium channel clusters

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

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

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

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

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

A. Atria fill after ventricles relax
B. Ventricles fill after atria contract
C. Atria fill after ventricles contract
D. Ventricles fill after atria relax

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

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

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

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

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

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

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

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

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

A drug that blocks calcium-sodium channels in ventricular muscle reduces the inward current that maintains the long plateau phase (Phase _____) of the ventricular action potential.

Compared with skeletal muscle, which membrane property of cardiac muscle most directly contributes to the sustained action potential plateau?

A. Fivefold increase in calcium permeability following depolarization

B. Fivefold decrease in calcium permeability following depolarization

C. Fivefold increase in potassium permeability following depolarization

D. Fivefold decrease in potassium permeability following depolarization

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

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

Which refractory timing pair is normal for cardiac muscle?

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

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

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

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

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

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

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

Once present in the sarcoplasm, calcium most directly binds:

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

In cardiac and skeletal muscle, the binding of calcium to troponin C directly triggers which event to allow contraction?

A. Active extrusion of sodium

B. Conformational displacement of tropomyosin, exposing actin-binding sites for cross-bridge formation

C. Opening of gap junctions to allow intercellular ionic flow

D. Activation of SERCA pumps for sarcoplasmic reticulum calcium reuptake

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

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

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

A. Relaxing
B. Conducting
C. Filling
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

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

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

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

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

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

Each normal cardiac cycle is initiated by the:

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

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

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

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

Which mechanism best explains the benefit of atrial contraction immediately before ventricular systole?
A) Increases ventricular end-diastolic volume
B) Opens semilunar valves earlier
C) Decreases ventricular afterload
D) Enhances coronary perfusion during systole

The period of cardiac relaxation is called:

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

The period of cardiac contraction is called:

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

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

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

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 normal upright T wave on ECG most directly represents:

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

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

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

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

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

During ventricular systole, substantial blood accumulates within the:

A. Ventricles
B. Great arteries
C. Coronary sinuses
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

During which phase of the cardiac cycle do the ventricles generate rapidly increasing pressure while both the AV and semilunar valves remain closed?
A) Rapid ventricular filling
B) Isovolumic relaxation
C) Isovolumic contraction
D) Ventricular ejection

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

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

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

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

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

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

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

Papillary muscles contract when the:

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

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

Dysfunction of papillary muscles or chordae tendineae can cause:

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

Compared with semilunar valves, AV valve closure is generally:

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

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

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

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

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

The valve type exposed to greater mechanical abrasion is the:

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

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

The incisura occurs because of a brief:

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

Loss of normal papillary muscle function leads to which mechanical failure during ventricular systole?

A. Prolapse or inversion of atrioventricular valve leaflets into the atrium

B. Inability of semilunar valve cusps to open during ejection

C. Impaired electrical conduction through the SA node

D. Loss of active atrial contraction during presystole

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

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

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

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

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

Minute work output is equal to:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Which primary mechanisms regulate total cardiac output (the volume of blood pumped by the heart per minute)?

A. Endocardial valve surface area and systemic venous tone
B. Intrinsic autoregulation and ANS input
C. Autoregulation of coronary blood flow alone
D. Papillary muscle contraction force and chordae tendineae tension

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

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

Parasympathetic vagal fibers are distributed mainly in the:

A. Ventricles
B. Purkinje system
C. Interventricular septum
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

Excess extracellular calcium most characteristically causes the heart to undergo:

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

Which measure more directly tracks chemical energy use?

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

Which change most directly increases left ventricular work?

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

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

Specialized cardiac tissue is best divided into:

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

Specialized cardiac conducting fibers (such as Purkinje fibers and SA node tissue) contract weakly compared to atrial and ventricular myocytes primarily because they contain:

A. Excessive density of intercalated discs

B. Very few myofibrils and contractile filaments

C. Markedly reduced resting membrane potassium permeability

D. Severely depleted sarcoplasmic calcium stores

Under routine light microscopy, the prominent dark transverse bands that cross cardiac muscle fibers at cell-to-cell junctions are known as:

A. Z lines (Z discs)

B. Transverse (T) tubules

C. Sarcoplasmic reticulum cisternae

D. Intercalated discs

At each intercalated disc, cell membranes form permeable:

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

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

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

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

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

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

During phase 1, the fast sodium channels:

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

During phase 1, which ion also leaves the cell?

A. calcium
B. chloride
C. sodium
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

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

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

The resting membrane potential in phase 4 is closest to:

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

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

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

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

The tricuspid and mitral valves are classified as:

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

The aortic and pulmonary valves are examples of:

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

Which valve type is supported by chordae tendineae?

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

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

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

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

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

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

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

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

Maximum efficiency of the normal heart is usually:

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

A patient with normal cardiac function receives a rapid intravenous normal saline bolus, increasing end-diastolic volume (preload). According to intrinsic cardiac autoregulation (the Frank-Starling law of the heart), what is the immediate effect on ventricular performance?

A. Decreased myocardial stretch, leading to weaker contraction and weaker stroke volume

B. Decreased myocardial stretch, leading to stronger contraction and increased stroke volume

C. Increased myocardial stretch, leading to stronger contraction and increased stroke volume

D. Increased myocardial stretch, leading to weaker contraction and weaker stroke volume

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