Cardiac Anatomy & Physiology

Explore the heart’s general features: a muscular pump that delivers blood to all tissues, with about 70 ml stroke volume at 75 bpm, located in the mediastinum within the pericardium.

Explore the external anatomy of the heart, including the four chambers and atrial appendages, and trace blood flow from the right atrium through the right ventricle to the pulmonary trunk.

Examine the cardiac arteries and their branches, including the right and left coronary arteries, right marginal, posterior interventricular, left circumflex, diagonal, and left marginal branches, and coronary dominance.

Explore the cardiac vasculature by tracing the coronary veins—the great cardiac vein, oblique vein, middle cardiac vein, interior cardiac vein, and the coronary sinus—from interventricular sulcus to the right atrium.

Explore the heart anatomy: right atrium with vena cava openings, fossa ovalis and coronary sinus, tricuspid valve, right ventricle with papillary muscles, moderator and septal bands, and left heart valves.

Explain the cardiac valves—the atrioventricular and semilunar valves—and their fibrous skeleton, cusps, and chordae, and how valve closure generates S1 and S2 heard across standard auscultation regions.

Autonomic innervation regulates heart rate and contractility through baroreceptors in the carotid sinus and aortic arch that signal via IX and X to the NTS, balancing sympathetic and parasympathetic outputs.

Explore the cardiac conduction system, from the SA node and internodal pathways to the AV node, bundle of His, and Purkinje fibers, and understand delays that ensure ventricular filling.

Examine cardiac muscle histology, including endocardium, myocardium, epicardium, and pericardial layers, intercalated discs, fascia adherens, desmosomes, and gap junctions enabling synchronized contraction.

The heart acts as an endocrine gland, secreting ANP from atria and BNP from ventricles in response to volume and pressure overload, promoting vasodilation and reducing blood pressure.

Explore cardiac muscle ultrastructure, detailing the sarcomere with thick and thin filaments, titin, CapZ capping protein, troponin–tropomyosin regulation, and the calcium-release diad with t-tubules triggering contraction.

Explore the ionic basis of cardiac electrical signaling by analyzing chemical and electrical gradients, equilibrium potentials, and the resting membrane potential shaped by potassium leak channels and the Na/K pump.

Examine the ionic basis of cardiac action potential by tracing sodium-driven depolarization, calcium entry via L-type channels, potassium efflux, and how the Na+/K+ ATPase resets resting gradients for another beat.

Explain how pacemaker cells in the sinoatrial and AV nodes generate electrical signals that set heart rate through diastolic polarization, the funny current via HCN channels, and potassium currents.

Explore how cardiac action potentials in cardiomyocytes unfold through four phases, driven by Na_v1.5, Cav1.2, NCX, and delayed rectifier potassium channels, lasting ~300 ms to prevent tetanus.

Learn how cardiac electrical signals propagate to synchronize heart contractions, with intercalated disks and gap junctions enabling sodium and calcium currents between cells, described by Ohm's law.

Explore cardiac excitation-contraction coupling: an action potential activates L-type calcium channels, triggering calcium-induced calcium release from the sarcoplasmic reticulum, increasing intracellular calcium to drive cross-bridge cycling and contraction.

Calcium-induced calcium release and calcium sparks raise calcium, bind troponin, shift tropomyosin, exposing actin sites to enable cross-bridge cycling with myosin powered by ATP and Pi through power stroke.

Understand how the autonomic nervous system controls heart rate by modulating pacemaker cells: sympathetic beta-1 signaling raises cAMP and If, while parasympathetic acetylcholine lowers rate via Gi and IKach.

Explore how the autonomic nervous system regulates cardiac contractility, detailing sympathetic beta-1 receptor activation increasing calcium transients via cAMP-PKA, and parasympathetic and adenosine pathways causing negative inotropy.

Master the basics of the electrocardiogram, including electrode polarity, bipolar and unipolar leads, and the mean electrical axis. Understand the P, QRS, and T waves, and the isoelectric line.

Determine the mean electrical axis from r-wave peaks across leads, or from the most isoelectric lead, using the circle of axes and perpendiculars.

Explore cardiac cycle from atrial systole to ventricular systole and diastole, highlighting right and left heart pressures across pulmonary and systemic circulations, valve closures, and ecg with s1 and s2.

Cardiac output equals heart rate times stroke volume and ranges from 5 to 6 liters per minute. Preload, afterload, and contractility shape stroke volume and EDV/ESV balance.

Demonstrate how preload and sarcomere length raise active and passive tension in cardiac muscle, and explain the Frank-Starling mechanism linking venous return to increased stroke volume.

Examine how preload and afterload shape the cardiac force-velocity relationship, including isometric and isotonic contractions, the peak fmax and vmax influenced by myosin isoforms alpha and beta and contractility.

Explore the cardiac pressure-volume relationship, define end diastolic volume, and show how atrial systole, isovolumetric phases, afterload, and Frank-Starling shape stroke volume.