Cardiac Physiology Study Guide (2025/2026 Syllabus)
This guide covers the core principles of cardiac function, from cellular electrophysiology
to integrated hemodynamics, preparing you for advanced understanding in clinical
contexts.
Section 1: Anatomy & Histology of the Heart
1. What are the two main types of cardiac muscle cells and their primary
functions?
ANSWER ✓ The two main types are contractile cardiomyocytes (99% of cells,
responsible for the mechanical work of pumping blood) and pacemaker/conducting
cells (1% of cells, responsible for generating and rapidly conducting electrical impulses
to coordinate contraction).
2. Describe the path of blood flow through the heart chambers and valves.
ANSWER ✓ Blood flows from the body → Superior/Inferior Vena Cava → Right Atrium →
Tricuspid Valve → Right Ventricle → Pulmonary Valve → Pulmonary Arteries → Lungs →
Pulmonary Veins → Left Atrium → Mitral Valve → Left Ventricle → Aortic Valve → Aorta
→ Body.
3. What is the functional significance of the intercalated discs in cardiac muscle?
ANSWER ✓ Intercalated discs contain desmosomes for strong mechanical adhesion
and gap junctions that allow for the rapid passage of ions, enabling the myocardium to
function as a single, coordinated unit known as a functional syncytium.
4. Why is the left ventricular myocardium significantly thicker than the right?
ANSWER ✓ The left ventricle must generate much higher pressure to overcome the
systemic vascular resistance and pump blood throughout the entire body, whereas the
right ventricle only pumps blood to the low-resistance pulmonary circulation.
5. What is the purpose of the fibrous cardiac skeleton?
ANSWER ✓ It serves as a structural framework, electrically insulates the atria from the
ventricles, and provides attachment points for the heart valves and cardiac muscle.
, Section 2: Cardiac Electrophysiology & The Action Potential
6. Define automaticity and identify the primary pacemaker of the heart.
ANSWER ✓ Automaticity is the ability of cardiac cells to spontaneously generate an
action potential without external stimulation. The Sinoatrial (SA) Node is the primary
pacemaker.
7. Contrast the action potentials of ventricular myocytes and SA node cells.
ANSWER ✓ Ventricular Myocytes: Have a stable resting potential (-90mV), a rapid
upstroke (Phase 0) from fast Na+ channels, and a long plateau (Phase 2) from Ca2+
influx. SA Node Cells: Have an unstable resting potential (pacemaker potential), a
slower upstroke (Phase 0) from Ca2+ channels, and no true plateau.
8. What ion is primarily responsible for the pacemaker potential (diastolic
depolarization) in the SA node?
ANSWER ✓ The "funny current" (I_f), a mixed Na+/K+ current that opens at
hyperpolarized potentials, is the primary initiator. Reduced K+ efflux and increased
Ca2+ influx (T-type) then complete the depolarization.
9. What is the role of the long refractory period in cardiac muscle?
ANSWER ✓ It prevents tetanus (sustained contraction) by ensuring the heart can relax
and fill with blood between beats. This is crucial for the heart's function as a pump.
10. How do fast sodium channels differ from slow calcium channels in cardiac
action potentials?
ANSWER ✓ Fast Na+ channels activate and inactivate quickly, are highly voltage-
sensitive, and are responsible for the rapid depolarization in non-pacemaker cells. Slow
L-type Ca2+ channels activate more slowly, conduct Ca2+, and are responsible for the
plateau phase and pacemaker depolarization.
11. What effect does sympathetic stimulation have on the slope of the pacemaker
potential?
ANSWER ✓ Sympathetic stimulation (via norepinephrine/epinephrine on β1-adrenergic
receptors) increases the slope of the pacemaker potential, leading to a faster heart rate
(positive chronotropy).
This guide covers the core principles of cardiac function, from cellular electrophysiology
to integrated hemodynamics, preparing you for advanced understanding in clinical
contexts.
Section 1: Anatomy & Histology of the Heart
1. What are the two main types of cardiac muscle cells and their primary
functions?
ANSWER ✓ The two main types are contractile cardiomyocytes (99% of cells,
responsible for the mechanical work of pumping blood) and pacemaker/conducting
cells (1% of cells, responsible for generating and rapidly conducting electrical impulses
to coordinate contraction).
2. Describe the path of blood flow through the heart chambers and valves.
ANSWER ✓ Blood flows from the body → Superior/Inferior Vena Cava → Right Atrium →
Tricuspid Valve → Right Ventricle → Pulmonary Valve → Pulmonary Arteries → Lungs →
Pulmonary Veins → Left Atrium → Mitral Valve → Left Ventricle → Aortic Valve → Aorta
→ Body.
3. What is the functional significance of the intercalated discs in cardiac muscle?
ANSWER ✓ Intercalated discs contain desmosomes for strong mechanical adhesion
and gap junctions that allow for the rapid passage of ions, enabling the myocardium to
function as a single, coordinated unit known as a functional syncytium.
4. Why is the left ventricular myocardium significantly thicker than the right?
ANSWER ✓ The left ventricle must generate much higher pressure to overcome the
systemic vascular resistance and pump blood throughout the entire body, whereas the
right ventricle only pumps blood to the low-resistance pulmonary circulation.
5. What is the purpose of the fibrous cardiac skeleton?
ANSWER ✓ It serves as a structural framework, electrically insulates the atria from the
ventricles, and provides attachment points for the heart valves and cardiac muscle.
, Section 2: Cardiac Electrophysiology & The Action Potential
6. Define automaticity and identify the primary pacemaker of the heart.
ANSWER ✓ Automaticity is the ability of cardiac cells to spontaneously generate an
action potential without external stimulation. The Sinoatrial (SA) Node is the primary
pacemaker.
7. Contrast the action potentials of ventricular myocytes and SA node cells.
ANSWER ✓ Ventricular Myocytes: Have a stable resting potential (-90mV), a rapid
upstroke (Phase 0) from fast Na+ channels, and a long plateau (Phase 2) from Ca2+
influx. SA Node Cells: Have an unstable resting potential (pacemaker potential), a
slower upstroke (Phase 0) from Ca2+ channels, and no true plateau.
8. What ion is primarily responsible for the pacemaker potential (diastolic
depolarization) in the SA node?
ANSWER ✓ The "funny current" (I_f), a mixed Na+/K+ current that opens at
hyperpolarized potentials, is the primary initiator. Reduced K+ efflux and increased
Ca2+ influx (T-type) then complete the depolarization.
9. What is the role of the long refractory period in cardiac muscle?
ANSWER ✓ It prevents tetanus (sustained contraction) by ensuring the heart can relax
and fill with blood between beats. This is crucial for the heart's function as a pump.
10. How do fast sodium channels differ from slow calcium channels in cardiac
action potentials?
ANSWER ✓ Fast Na+ channels activate and inactivate quickly, are highly voltage-
sensitive, and are responsible for the rapid depolarization in non-pacemaker cells. Slow
L-type Ca2+ channels activate more slowly, conduct Ca2+, and are responsible for the
plateau phase and pacemaker depolarization.
11. What effect does sympathetic stimulation have on the slope of the pacemaker
potential?
ANSWER ✓ Sympathetic stimulation (via norepinephrine/epinephrine on β1-adrenergic
receptors) increases the slope of the pacemaker potential, leading to a faster heart rate
(positive chronotropy).
