Cardiac Anatomy, Physiology, and Action Potential Mechanics
What are the four chambers of the heart? - correct answer Right atrium, right ventricle, left
atrium, left ventricle.
How do the right and left sides of the heart function? - correct answer Right heart pumps blood
through lungs; left heart pumps blood through systemic circulation.
What is the circulation path of blood through the right heart? - correct answer Right atrium →
tricuspid valve → right ventricle → pulmonary semilunar valve → pulmonary trunk →
pulmonary arteries → lungs.
What is the circulation path of blood through the left heart? - correct answer Pulmonary veins
→ left atrium → mitral valve → left ventricle → aortic semilunar valve → aorta → systemic
circulation.
What structures does blood pass through from the superior vena cava to the aorta? - correct
answer SVC/IVC/coronary sinus → right atrium → tricuspid → right ventricle → pulmonary
valve → pulmonary arteries → lungs → pulmonary veins → left atrium → mitral valve → left
ventricle → aortic valve → aorta.
What is the role of the tricuspid and mitral valves? - correct answer They prevent backflow into
the atria.
What is the role of the pulmonary and aortic semilunar valves? - correct answer They prevent
backflow into the ventricles.
What is the complete flow of blood starting from systemic veins? - correct answer Systemic
veins → right heart → pulmonary circulation → left heart → systemic arteries.
What is the significance of the coronary sinus? - correct answer It collects venous blood from
myocardium and drains into the right atrium.
What are the three major types of cardiac muscle fibers? - correct answer Atrial muscle,
ventricular muscle (contractile), and specialized excitatory/conductive fibers.
How do atrial and ventricular muscle fibers compare to skeletal muscle fibers? - correct answer
They contract like skeletal muscle but have longer contraction durations.
What is the function of specialized excitatory and conductive fibers? - correct answer They
generate and conduct action potentials.
How do specialized fibers contribute to automatic rhythmic electrical discharge? - correct
answer They produce rhythmic electrical discharges (pacemaker potentials).
How are cardiac muscle fibers arranged? - correct answer They branch and interconnect in a
latticework pattern.
,How does the arrangement of fibers contribute to the functional syncytium of the heart? -
correct answer It allows impulses to spread rapidly in all directions.
What are the similarities between cardiac and skeletal muscle structure? - correct answer Both
are striated and rely on the sliding filament mechanism.
How does cardiac muscle contraction differ in duration from skeletal muscle contraction? -
correct answer Cardiac contractions last much longer due to calcium influx and plateau.
What does the term 'syncytium' mean in cardiac muscle? - correct answer Syncytium = network
of cells acting as a single unit.
What is the role of intercalated discs in the cardiac syncytium? - correct answer They connect
cells for electrical continuity.
How do gap junctions contribute to electrical coupling between cardiac cells? - correct answer
They allow ions to pass quickly between cells.
How do ions move between cardiac cells? - correct answer Ions diffuse rapidly, spreading
depolarization through tissue.
What distinguishes the atrial syncytium from the ventricular syncytium? - correct answer Atrial
syncytium contracts separately from ventricular syncytium.
Why are the atria and ventricles separated by fibrous tissue? - correct answer Fibrous tissue
insulates atria from ventricles except at AV bundle.
What is the function of the atrioventricular (AV) bundle? - correct answer It carries impulses
from atria to ventricles.
Why is it important for the atria to contract slightly before the ventricles? - correct answer It
ensures ventricles fill before they contract.
What initiates a cardiac muscle action potential? - correct answer Depolarization from adjacent
cells via gap junctions.
What is the resting membrane potential of cardiac muscle cells? - correct answer Resting
potential -85 to -90 mV; threshold about -70 mV.
How is the action potential initiated by neighboring cells? - correct answer Local depolarization
raises potential to threshold, triggering Na+ influx.
What are the five phases of the cardiac action potential? - correct answer Phase 0:
depolarization; 1: initial repolarization; 2: plateau; 3: rapid repolarization; 4: resting.
What ionic movements occur in each phase of the cardiac action potential? - correct answer
Na+, Ca2+, and K+ movements determine each phase.
, What role do sodium channels play during phase 0? - correct answer Fast Na+ channels open,
Na+ enters, depolarization occurs.
What happens to membrane potential during phase 1? - correct answer Na+ channels close, K+
channels briefly open, slight repolarization.
Why does the plateau phase occur in cardiac muscle? - correct answer Due to Ca2+ influx
balancing K+ efflux; not seen in skeletal muscle.
What is the role of calcium influx through L-type calcium channels? - correct answer It
maintains the plateau.
What changes occur in potassium permeability during the plateau phase? - correct answer K+
permeability decreases early, delaying repolarization.
What occurs during phase 3 of the cardiac action potential? - correct answer Ca2+ channels
close, K+ channels open fully, membrane repolarizes.
What happens during phase 4? - correct answer Resting potential reestablished at about -90
mV.
What is the function of the Na⁺/K⁺ pump in maintaining resting potential? - correct answer It
maintains ionic balance.
How do action potentials in cardiac muscle compare to those in skeletal muscle? - correct
answer Cardiac AP lasts 200-300 ms; skeletal lasts a few ms.
Why is the cardiac action potential longer? - correct answer Ca2+ channels open longer,
causing extended depolarization.
Which ion channels are responsible for the plateau phase? - correct answer Slow L-type Ca2+
and slow K+ channels.
How does calcium influx trigger contraction in cardiac muscle? - correct answer Calcium enters
from extracellular space, triggers contraction.
How does the source of calcium differ in cardiac and skeletal muscle contraction? - correct
answer Skeletal muscle calcium from SR; cardiac from both SR and extracellular fluid.
How does the long plateau phase affect cardiac muscle contraction? - correct answer It allows
longer, stronger contraction to eject blood effectively.
What is the function of slow L-type calcium channels? - correct answer They maintain
depolarization.
What allows longer, stronger contraction to eject blood effectively? - correct answer Slow L-
type calcium channels.
What are the four chambers of the heart? - correct answer Right atrium, right ventricle, left
atrium, left ventricle.
How do the right and left sides of the heart function? - correct answer Right heart pumps blood
through lungs; left heart pumps blood through systemic circulation.
What is the circulation path of blood through the right heart? - correct answer Right atrium →
tricuspid valve → right ventricle → pulmonary semilunar valve → pulmonary trunk →
pulmonary arteries → lungs.
What is the circulation path of blood through the left heart? - correct answer Pulmonary veins
→ left atrium → mitral valve → left ventricle → aortic semilunar valve → aorta → systemic
circulation.
What structures does blood pass through from the superior vena cava to the aorta? - correct
answer SVC/IVC/coronary sinus → right atrium → tricuspid → right ventricle → pulmonary
valve → pulmonary arteries → lungs → pulmonary veins → left atrium → mitral valve → left
ventricle → aortic valve → aorta.
What is the role of the tricuspid and mitral valves? - correct answer They prevent backflow into
the atria.
What is the role of the pulmonary and aortic semilunar valves? - correct answer They prevent
backflow into the ventricles.
What is the complete flow of blood starting from systemic veins? - correct answer Systemic
veins → right heart → pulmonary circulation → left heart → systemic arteries.
What is the significance of the coronary sinus? - correct answer It collects venous blood from
myocardium and drains into the right atrium.
What are the three major types of cardiac muscle fibers? - correct answer Atrial muscle,
ventricular muscle (contractile), and specialized excitatory/conductive fibers.
How do atrial and ventricular muscle fibers compare to skeletal muscle fibers? - correct answer
They contract like skeletal muscle but have longer contraction durations.
What is the function of specialized excitatory and conductive fibers? - correct answer They
generate and conduct action potentials.
How do specialized fibers contribute to automatic rhythmic electrical discharge? - correct
answer They produce rhythmic electrical discharges (pacemaker potentials).
How are cardiac muscle fibers arranged? - correct answer They branch and interconnect in a
latticework pattern.
,How does the arrangement of fibers contribute to the functional syncytium of the heart? -
correct answer It allows impulses to spread rapidly in all directions.
What are the similarities between cardiac and skeletal muscle structure? - correct answer Both
are striated and rely on the sliding filament mechanism.
How does cardiac muscle contraction differ in duration from skeletal muscle contraction? -
correct answer Cardiac contractions last much longer due to calcium influx and plateau.
What does the term 'syncytium' mean in cardiac muscle? - correct answer Syncytium = network
of cells acting as a single unit.
What is the role of intercalated discs in the cardiac syncytium? - correct answer They connect
cells for electrical continuity.
How do gap junctions contribute to electrical coupling between cardiac cells? - correct answer
They allow ions to pass quickly between cells.
How do ions move between cardiac cells? - correct answer Ions diffuse rapidly, spreading
depolarization through tissue.
What distinguishes the atrial syncytium from the ventricular syncytium? - correct answer Atrial
syncytium contracts separately from ventricular syncytium.
Why are the atria and ventricles separated by fibrous tissue? - correct answer Fibrous tissue
insulates atria from ventricles except at AV bundle.
What is the function of the atrioventricular (AV) bundle? - correct answer It carries impulses
from atria to ventricles.
Why is it important for the atria to contract slightly before the ventricles? - correct answer It
ensures ventricles fill before they contract.
What initiates a cardiac muscle action potential? - correct answer Depolarization from adjacent
cells via gap junctions.
What is the resting membrane potential of cardiac muscle cells? - correct answer Resting
potential -85 to -90 mV; threshold about -70 mV.
How is the action potential initiated by neighboring cells? - correct answer Local depolarization
raises potential to threshold, triggering Na+ influx.
What are the five phases of the cardiac action potential? - correct answer Phase 0:
depolarization; 1: initial repolarization; 2: plateau; 3: rapid repolarization; 4: resting.
What ionic movements occur in each phase of the cardiac action potential? - correct answer
Na+, Ca2+, and K+ movements determine each phase.
, What role do sodium channels play during phase 0? - correct answer Fast Na+ channels open,
Na+ enters, depolarization occurs.
What happens to membrane potential during phase 1? - correct answer Na+ channels close, K+
channels briefly open, slight repolarization.
Why does the plateau phase occur in cardiac muscle? - correct answer Due to Ca2+ influx
balancing K+ efflux; not seen in skeletal muscle.
What is the role of calcium influx through L-type calcium channels? - correct answer It
maintains the plateau.
What changes occur in potassium permeability during the plateau phase? - correct answer K+
permeability decreases early, delaying repolarization.
What occurs during phase 3 of the cardiac action potential? - correct answer Ca2+ channels
close, K+ channels open fully, membrane repolarizes.
What happens during phase 4? - correct answer Resting potential reestablished at about -90
mV.
What is the function of the Na⁺/K⁺ pump in maintaining resting potential? - correct answer It
maintains ionic balance.
How do action potentials in cardiac muscle compare to those in skeletal muscle? - correct
answer Cardiac AP lasts 200-300 ms; skeletal lasts a few ms.
Why is the cardiac action potential longer? - correct answer Ca2+ channels open longer,
causing extended depolarization.
Which ion channels are responsible for the plateau phase? - correct answer Slow L-type Ca2+
and slow K+ channels.
How does calcium influx trigger contraction in cardiac muscle? - correct answer Calcium enters
from extracellular space, triggers contraction.
How does the source of calcium differ in cardiac and skeletal muscle contraction? - correct
answer Skeletal muscle calcium from SR; cardiac from both SR and extracellular fluid.
How does the long plateau phase affect cardiac muscle contraction? - correct answer It allows
longer, stronger contraction to eject blood effectively.
What is the function of slow L-type calcium channels? - correct answer They maintain
depolarization.
What allows longer, stronger contraction to eject blood effectively? - correct answer Slow L-
type calcium channels.
