Cardiac Structure & Coronary Circulation
1. Which chamber of the heart generates the greatest pressure and why is this
physiologically necessary?
Answer: The left ventricle, because it pumps blood into systemic circulation which has
higher resistance than pulmonary circulation.
2. What would happen if the mitral valve became stenotic in terms of preload and
pulmonary circulation?
Answer: Preload to the left ventricle decreases, left atrial pressure increases, leading to
pulmonary congestion and possibly pulmonary edema.
3. Explain how right coronary artery occlusion can lead to bradyarrhythmias.
Answer: The RCA often supplies the SA node (60%) and AV node (80%); ischemia here
can impair pacemaker/conduction tissue function.
4. Which coronary artery is most often associated with “widow-maker” infarctions and
why?
Answer: The left anterior descending (LAD) artery, because it supplies a large portion of
the left ventricle and interventricular septum.
Cardiac Action Potentials
5. Why do pacemaker cells lack a true resting membrane potential compared to contractile
cells?
Answer: Because of “funny” sodium (If) channels that allow continuous depolarization
during diastole, giving them automaticity.
6. During which phase of the contractile cell action potential does calcium influx through L-
type channels balance potassium efflux, and why is this phase important?
Answer: Phase 2 (plateau); it prolongs depolarization, allowing sufficient time for
ventricular contraction and blood ejection.
7. Which ion movement primarily drives phase 0 depolarization in pacemaker cells, and
how is this different from contractile cells?
Answer: Calcium influx (via L-type channels) in pacemaker cells, versus sodium influx
in contractile cells.
8. Explain why blocking L-type calcium channels affects both pacemaker rhythm and
contractility.
Answer: In pacemaker cells, calcium influx mediates depolarization; in contractile cells,
it triggers calcium-induced calcium release needed for contraction.
Electrolyte Imbalances
9. How does hyperkalemia shorten the action potential duration?
Answer: Increased extracellular K⁺ enhances repolarization (phase 3), speeding
potassium efflux.
1. Which chamber of the heart generates the greatest pressure and why is this
physiologically necessary?
Answer: The left ventricle, because it pumps blood into systemic circulation which has
higher resistance than pulmonary circulation.
2. What would happen if the mitral valve became stenotic in terms of preload and
pulmonary circulation?
Answer: Preload to the left ventricle decreases, left atrial pressure increases, leading to
pulmonary congestion and possibly pulmonary edema.
3. Explain how right coronary artery occlusion can lead to bradyarrhythmias.
Answer: The RCA often supplies the SA node (60%) and AV node (80%); ischemia here
can impair pacemaker/conduction tissue function.
4. Which coronary artery is most often associated with “widow-maker” infarctions and
why?
Answer: The left anterior descending (LAD) artery, because it supplies a large portion of
the left ventricle and interventricular septum.
Cardiac Action Potentials
5. Why do pacemaker cells lack a true resting membrane potential compared to contractile
cells?
Answer: Because of “funny” sodium (If) channels that allow continuous depolarization
during diastole, giving them automaticity.
6. During which phase of the contractile cell action potential does calcium influx through L-
type channels balance potassium efflux, and why is this phase important?
Answer: Phase 2 (plateau); it prolongs depolarization, allowing sufficient time for
ventricular contraction and blood ejection.
7. Which ion movement primarily drives phase 0 depolarization in pacemaker cells, and
how is this different from contractile cells?
Answer: Calcium influx (via L-type channels) in pacemaker cells, versus sodium influx
in contractile cells.
8. Explain why blocking L-type calcium channels affects both pacemaker rhythm and
contractility.
Answer: In pacemaker cells, calcium influx mediates depolarization; in contractile cells,
it triggers calcium-induced calcium release needed for contraction.
Electrolyte Imbalances
9. How does hyperkalemia shorten the action potential duration?
Answer: Increased extracellular K⁺ enhances repolarization (phase 3), speeding
potassium efflux.
