Cardiovascular System: Heart — Page-by-Page Comprehensive Study Notes

Page 1

• Topic: Cardiovascular System – Heart (intro/title slide by Sayed A. Baqeri).
• Purpose: Frame the heart as central component of cardiovascular system.

Page 2

• Learning objectives:
  • Identify and describe interior and exterior parts of the human heart.
  • Describe the path of blood through the cardiac circuits.
  • Describe the size, shape, and location of the heart.
  • Compare cardiac muscle to skeletal and smooth muscle.
  • Explain the cardiac conduction system.
  • Describe the process and purpose of an electrocardiogram (ECG).
  • Explain the cardiac cycle.
• Learning Objects (conceptual focus areas).

Page 3

• Learning objectives continuation:
  • Calculate cardiac output.
  • Describe effects of exercise on cardiac output and heart rate.
  • Name the brain centers that control heart rate and describe their function.
  • Identify other factors affecting heart rate.
  • Describe fetal heart development.

Page 4

• Group Discussion I topics:
  1) Describe the overall anatomy of the heart.
  2) Describe the overall blood circulation cycle through the heart.
  3) What are the coverings of the heart?
  4) What are the layers of the heart wall?
  5) How do the veins and arteries carrying blood from/to the heart differ?
  6) What are the veins emptying blood into the heart?
  7) What are the arteries taking blood away from the heart?

Page 5

• Content: Not provided in transcript. Note: no reader-facing content.

Page 6

• Heart anatomy basics:
  • Location: within the thoracic cavity, medially between the lungs in the mediastinum.
  • Orientation: the heart extends obliquely for about 12$-$14$\text{ cm} (about 5 inches) from the 2nd rib to the 5th intercostal space.
  • Encased in the pericardial cavity.
• Practical note: relationship to nearby structures (lungs, diaphragm, etc.).

Page 7

• Surface anatomy (anterior view sketch cues):
  • Superior vena cava, Pulmonary trunk, Aorta, Apex of the heart, Left lung, Parietal pleura (cut), Pericardium (cut), Diaphragm.

Page 8

• Content: Not provided in transcript.

Page 9

• Internal orientation and landmarks:
  • The inferior tip of the heart is the apex, located between the fourth and fifth ribs.
  • The right side of the heart is deflected anteriorly; the left side is deflected posteriorly.

Page 10

• Base of the heart:
  • The base is the broad, superior portion formed primarily by the left atrium and a smaller portion of the right atrium.

Page 11

• Chambers and circulation (overview):
  • Four chambers: two atria (receiving chambers) and two ventricles (pumping chambers).
  • Right and left atria receive blood; ventricles pump blood to the lungs (right) or to the rest of the body (left).
  • Function summary: atria push blood into ventricles; ventricles propel blood to lungs or body.

Page 12

• Right atrium internal anatomy:
  • Smooth-walled posterior portion; anterior portion has muscular ridges (pectinate muscles).
  • Crista terminalis (terminal crest) separates posterior and anterior regions.

Page 13

• Content: Not provided in transcript.

Page 14

• Anterior view of right atrium components (internal aspect):
  • Superior vena cava, Pectinate muscles, Crista terminalis, Interatrial septum, Fossa ovalis, Opening of inferior vena cava (IVC), Opening of coronary sinus, Interventricular sulcus, Ascending aorta.
  • Note: RA interior opened and folded in anatomy diagrams.

Page 15

• Fossa ovalis and foramen ovale:
  • The interatrial septum bears the shallow depression called the fossa ovalis, where an opening (foramen ovale) existed in the fetal heart.

Page 16

• Anterior view diagram cues (vascular layout):
  • Brachiocephalic trunk, Superior vena cava, Right pulmonary artery, Ascending aorta, Pulmonary trunk, Left common carotid artery, Left subclavian artery, Aortic arch, Ligamentum arteriosum, Left pulmonary artery, Left pulmonary veins, Right pulmonary veins, Right atrium, Right coronary artery, Anterior cardiac vein, Right ventricle, Right marginal artery, Small cardiac vein, Inferior vena cava, Auricle of left atrium, Circumflex artery, Left coronary artery, Great cardiac vein, Anterior interventricular artery, Apex.

Page 17

• Venous and pulmonary input:
  • Blood enters the right atrium via three sources: superior vena cava (blood from body regions above the diaphragm), inferior vena cava (blood from below the diaphragm), and coronary sinus (drains myocardium).
  • Four pulmonary veins enter the left atrium (blood from the lungs); posterior view highlights different venous inputs.

Page 18

• Ventricular anatomy and internal ridges:
  • Ventricles comprise most of the heart’s volume.
  • Right ventricle forms most of the heart’s anterior surface; left ventricle dominates the posteroinferior surface.
  • Internal ridges: trabeculae carneae (crossbars of flesh).
  • Papillary muscles project into the ventricular cavity and play a role in valve function.

Page 19

• Content: Not provided in transcript.

Page 20

• Related concepts and anatomy cues:
  • Papillary muscles, Mitral valve, Right ventricle, Aorta, Interventricular septum, Left atrium, Left ventricle (diagram prompts).

Page 21

• Cardiac circuits overview:
  • Pulmonary circuit: transports blood to and from the lungs for gas exchange (oxygenation of blood, CO2 removal).
  • Systemic circuit: transports oxygenated blood to the body and returns deoxygenated blood to the heart.
  • Pulmonary circuit is short, low-pressure; systemic circuit is long, high-pressure, high-friction.

Page 22

• Major aortic and coronary landmarks (anterior view):
  • Left subclavian artery, Left common carotid artery, Brachiocephalic trunk, Ascending aorta, Aortic arch, Ligamentum arteriosum, Pulmonary trunk, Right atrium, Right coronary artery, Anterior interventricular artery, Left ventricle, Great cardiac vein, Anterior interventricular sulcus, (left coronary artery branches).

Page 23

• Systemic circuit details:
  • Transports oxygenated blood to body tissues; returns deoxygenated blood and CO2 to the heart.
  • High-pressure, high-friction circulation.
  • After systemic circulation, blood returns to the pulmonary circuit for reoxygenation.

Page 24

• Blood ejection pathways:
  • Right ventricle pumps deoxygenated blood into the pulmonary trunk → left and right pulmonary arteries → lungs (pulmonary circuit).
  • Left ventricle pumps oxygenated blood into the aorta → body (systemic circuit).

Page 25

• Diagrammatic recap of major vessels and chambers (anterior view).

Page 26

• Pulmonary inputs and systemic inputs recap:
  • Pulmonary veins bring oxygenated blood into the left atrium, which then pumps to the left ventricle.
  • Superior and inferior vena cavae return deoxygenated blood to the right atrium.
  • This is part of the pulmonary circuit (lungs) and systemic circuit (body).

Page 27

• Pericardial membranes:
  • Pericardium consists of two sublayers: fibrous pericardium and serous pericardium.

Page 28

• Details of serous pericardium:
  • Parietal pericardium (fused to fibrous pericardium).
  • Visceral pericardium or epicardium (fused to the heart wall, part of heart wall).
  • Pericardial cavity between visceral and parietal layers, filled with lubricating serous fluid.

Page 29

• Layers of the heart wall:
  • Epicardium (visceral pericardium): outer layer of the heart wall.
  • Myocardium: thick, middle layer of cardiac muscle responsible for pumping.
  • Endocardium: innermost lining of chambers and valves; continuous with endothelial lining of blood vessels.

Page 30

• Internal structure recap:
  • Four chambers: two atria, two ventricles.
  • Septa: interatrial septum, interventricular septum, and atrioventricular septum (separates atria from ventricles).

Page 31

• Credit/illustration note for chambers and vessels (Gray’s Anatomy reference).

Page 32

• Veins vs arteries rule:
  • Always: veins bring blood into the heart; arteries take it away.
  • General rule: veins carry deoxygenated blood; arteries carry oxygenated blood.
  • Exception: the vessels connected to the lungs (pulmonary circuit) carry opposite oxygenation status.

Page 33

• Reinforcement of chamber inputs:
  • SVC/IVC bring deoxygenated blood to the right atrium.
  • Pulmonary veins bring oxygenated blood from the lungs to the left atrium.

Page 34

• Pulmonary trunk and aorta:
  • Pulmonary trunk leads to pulmonary arteries (deoxygenated blood to lungs).
  • Aorta carries oxygenated blood to the systemic circulation.

Page 35

• Ventricular wall thickness:
  • Myocardium of the left ventricle is significantly thicker than that of the right ventricle.
  • Both ventricles pump the same overall amount of blood, but the left ventricle must generate greater pressure to overcome systemic resistance in the systemic circuit.

Page 36

• Group Discussion II topics:
  1) Types of heart valves and sub-types.
  2) Left and right pathway of blood through the heart.
  3) Coronary circulation.
  4) Coronary arteries: what they are and what they do.
  5) Difference between cardiac veins and the coronary sinus.

Page 37

• Heart valves overview:
  • Valves ensure one-way flow of blood.
  • Two types: atrioventricular (AV) valves between atria and ventricles; semilunar valves between ventricles and major arteries.

Page 38

• Content: Not provided in transcript.

Page 39

• AV valves details:
  • Right AV valve = tricuspid valve (three cusps).
  • Left AV valve = mitral (bicuspid) valve (two cusps).

Page 40

• Structural cross-section cues (cardiac skeleton) and valve anatomy:
  • Pulmonary valve, aortic valve (semilunar valves).
  • Mitral (left AV) and Tricuspid (right AV) valves.
  • Myocardium and plan of cutaway visuals.

Page 41

• Semilunar valves:
  • Openings between ventricles and the pulmonary trunk (pulmonary semilunar valve) and the aorta (aortic semilunar valve).

Page 42

• Details of the AV valves:
  • Tricuspid valve has three cusps.
  • Mitral valve has two cusps; its name derives from bishop’s mitre appearance.

Page 43

• Atrioventricular valve support structures:
  • Chordae tendineae connect valve cusps to papillary muscles.
  • Papillary muscles anchor to ventricular walls.
  • Function: chordae tendineae prevent valve flaps from everting into atria during ventricular contraction.

Page 44

• Diagrammatic relationships:
  • Right atrium with tricuspid valve; left atrium with mitral valve; papillary muscles and chordae tendineae illustrated.

Page 45

• Valve opening/closing sequence schematic (AV valves): 1) Blood returning to the heart fills atria; AV valves open. 2) As ventricles fill, AV valve cusps hang into ventricles. 3) Atria contract, forcing additional blood into ventricles.
  • Descriptions accompany diagrams of cusp alignment, chordae tendineae tension, and papillary muscles.

Page 46

• AV valve behavior:
  • Both AV valves open simultaneously due to atrial pressure; as ventricles fill, the valve flaps hang downward.
  • Chordae tendineae prevent valves from eversion into the atria.

Page 47

• Semilunar valves behavior:
  • Open simultaneously as ventricles contract and intraventricular pressure rises, forcing cusps open.
  • This contraction also closes the AV valves from the inside, preventing backflow into atria.

Page 48

• Semilunar valve mechanics (continued):
  • When ventricles relax, backflow from arteries closes semilunar valves.

Page 49

• Diagrammatic note: In same-sets of valves open/close in synchrony; valves of one set operate together.

Page 50

• Valve disorders:
  • Incompetent/valvular disease: valves do not function properly.
  • Prolapsed valve: a cusp is pushed backward by blood force.
  • Stenosis: valve becomes rigid and may calcify over time.

Page 51

• Double pump concept (diagram-driven):
  • Right side handles systemic venous return through vena cavae and coronary sinus; right AV valve (tricuspid) and right ventricle pump to pulmonary circulation via pulmonary trunk and arteries.
  • Left side handles oxygenated blood from lungs via four pulmonary veins into left atrium; left AV valve (mitral) and left ventricle pump to body via aorta.

Page 52

• Pathway of blood through the heart (summary):
  • Right side: SVC/IVC/Coronary sinus → Right atrium → Tricuspid valve → Right ventricle → Pulmonary semilunar valve → Pulmonary trunk → Pulmonary arteries → Lungs.
  • Left side: Four pulmonary veins → Left atrium → Mitral valve → Left ventricle → Aortic semilunar valve → Aorta → Systemic circulation.

Page 53

• Image credit and pericardial context (anatomical labels).

Page 54

• Coronary circulation overview:
  • A small circulation that supplies blood to cardiac muscle and heart components.
  • Not continuous; it cycles, peaking when the heart muscle is relaxed and nearly ceasing during contraction.
  • Two branches: coronary arteries and coronary veins.

Page 55

• Left coronary artery details:
  • Left coronary artery divides into two major branches:
  • Anterior interventricular artery (Left Anterior Descending, LAD): follows the anterior interventricular sulcus; supplies interventricular septum and anterior walls of both ventricles.
  • Circumflex artery: supplies left atrium and posterior walls of the left ventricle.

Page 56

• Diagrammatic mapping of major coronary arteries (anterior view).

Page 57

• Right coronary artery branches:
  • Right marginal artery: supplies lateral right side of heart.
  • Posterior interventricular artery: runs to heart apex; supplies posterior ventricular walls; anastomoses with the left anterior descending near the apex.

Page 58

• Coronary arteries visual reference (image).

Page 59

• Coronary veins recap:
  • Great cardiac vein follows the anterior interventricular sulcus; drains areas supplied by the LAD.
  • Middle cardiac vein drains areas supplied by the posterior interventricular artery.
  • Small cardiac vein runs along the heart’s right inferior margin.
  • All drain into the coronary sinus (drains into the right atrium).
  • Anterior cardiac vein drains the anterior surface of the right ventricle directly into the right atrium.

Page 60

• Diagrammatic corollary of major cardiac veins and coronary sinus.

Page 61

• Coronary arteries – credit and attribution (Blausen Medical Communications, CC BY 3.0).

Page 62

• Disorders of coronary circulation:
  • Atherosclerosis: hardening and plaque buildup in arteries (lipids, cholesterol, connective tissue, white blood cells, smooth muscle cells).
  • Ischemia: restricted blood flow causing hypoxia.
  • Myocardial infarction (heart attack): death of cardiac cells due to ischemia.

Page 63

• Cardiac muscle cell characteristics (compared to skeletal):
  • Cardiac muscle cells are shorter, striated, with a single central nucleus (sometimes multiple nuclei).
  • They branch freely.

Page 64

• Intercellular connections:
  • Intercalated discs join adjacent cardiomyocytes, enabling synchronized contraction (functional syncytium).
  • Desmosomes: prevent cells from pulling apart during contraction.
  • Gap junctions: allow ions to pass between cells, enabling electrical coupling across the myocardium.

Page 65

• Cardiac muscle cell structure (visual cues):
  • Short, branched, striated cells with intercalated discs, gap junctions, desmosomes.
  • Sarcolemma, nucleus, mitochondria, T-tubules, sarcoplasmic reticulum (no triads in cardiac muscle like skeletal muscle).

Page 66

• Mitochondrial content and fatigue resistance:
  • Abundant mitochondria account for about $35\%$ of the volume of cardiac cells (compared with $3-8\%$ in skeletal muscle fibers).
  • High ATP production confers fatigue resistance.

Page 67

• Cardiac muscle cell cross-section anatomy (desmosomes, gap junctions, etc.).

Page 68

• Group Discussion III prompts:
  1) Sequence of excitation in cardiac muscle; locations of nodes and bundles.
  2) Recognizing electrical wave patterns for different nodes.
  3) Definitions: arrhythmias, tachycardia, bradycardia.
  4) Steps of action potential in heart.
  5) Electrocardiography: what it is and why it’s important.
  6) Overall mechanical events of the heart.

Page 69

• Conduction system overview:
  • Cardiac muscle contracts even without nervous input (intrinsic rhythm).
  • Components (direction of signal): SA node → AV node → AV bundle (Bundle of His) → Purkinje/ subendocardial network.
  • Total time from SA initiation to ventricular depolarization ≈ $225\text{ ms}$.

Page 70

• Stepwise conduction path (visualized):
  1) SA node in right atrium; pacemaker.
  2) Internodal pathway to AV node; brief pause to allow atrial contraction.
  3) AV node delays impulse (≈100 ms).
  4) AV bundle connects atria to ventricles through interventricular septum.
  5) Bundle branches conduct impulses to apex.
  6) Subendocardial conducting network (Purkinje fibers) depolarizes contractile cells in ventricles.
• Pathway schematic includes: SA node → AV node → AV bundle → bundle branches → Purkinje network.

Page 71

• SA node details:
  • Location: superior/posterior walls of right atrium, inferior to SVC.
  • Inherent rate: ~$75\text{ beats/min}$; pacemaker of the heart; initiates sinus rhythm.

Page 72

• AV node details:
  • Location: inferior portion of right atrium within the AV septum.
  • Cell geometry causes delay; signals take ~$100\text{ ms}$ to pass through the node.
  • Inherent rate ~$50\text{ beats/min}$ without SA node input.

Page 73

• AV bundle and bundle branches:
  • AV bundle (Bundle of His) proceeds through the interventricular septum and electrically links atria to ventricles.
  • Left and right bundle branches conduct impulses toward the apex.

Page 74

• Subendocardial conducting network (Purkinje fibers):
  • Long strands of barrel-shaped cells with few myofibrils.
  • Penetrate apex and spread upward through ventricular walls.
  • Because stimulation begins at the apex, contraction starts at the apex and proceeds to the base, aiding effective ejection.

Page 75

• Conduction system sequence (labelled diagram prompts):
  • Start with SA node, then AV node, AV bundle, bundle branches, Purkinje fibers.

Page 76

• Pacemaker cell rates in the absence of other inputs:
  • SA node: ~$75\text{ bpm}$.
  • Without SA node input, AV node ~$50\text{ bpm}$.
  • Without AV node input, AV bundle/subendocardial network ~$30\text{ bpm}$.

Page 77

• Autonomic innervation basics:
  • Cardioaccelerator regions (sympathetic): stimulate SA and AV nodes, plus atria and ventricles.

Page 78

• Vagus nerve and parasympathetic influence:
  • Vagus nerve decreases heart rate (cardioinhibitory influence).
  • Key components: Dorsal motor nucleus of vagus, cardioinhibitory center, cardioacceleratory center, sympathetic trunk, sympathetic cardiac nerves, SA node, AV node.

Page 79

• Supplemental autonomic anatomy (illustrative):
  • Stellate ganglion, right/left sympathetic pathways, cervical/thoracic ganglia (C6, T1).

Page 80

• Content: Not provided in transcript.

Page 81

• Content: Not provided in transcript.

Page 82

• Redundant depiction of vagus nerve schematic and sympathetic pathways (paralleling Page 78).

Page 83

• Autonomic innervation summary:
  • Cardioinhibitory centers decrease heart activity via parasympathetic stimulation of the vagus nerve to SA and AV nodes.
  • At rest, both centers are active; vagal tone typically predominates.
  • Without regulation, SA node could drive ~$100\text{ bpm}$; resting heart rate is typically $60-100\text{ bpm}$.

Page 84

• Cardiac rhythm disorders:
  • Arrhythmias: irregular heart rhythms, can involve uncoordinated atrial/ventricular contractions.
  • Bradycardia: resting rate < $60\text{ bpm}$; athletes often have lower resting HR.
  • Tachycardia: resting rate > $100\text{ bpm}$.
  • Pediatric resting HRs can be higher than adult norms.

Page 85

• Action potentials in cardiac contractile cells – overview of phases:
  • Rapid depolarization, plateau, repolarization.
  • Long refractory periods enable effective pumping and prevent tetanus.

Page 86

• Depolarization details (phase 0):
  • Fast Na+ channels open; Na+ influx causes rapid depolarization; channels inactivate quickly.
  • Timeframe: short depolarization (ms-scale).
  • Contraction tension begins to develop during this phase.
  • Plateau phase maintains depolarization due to Ca2+ influx through slow Ca2+ channels; few K+ channels open.
  • Plateau duration: ~$175\text{ ms}$.

Page 87

• Na+ influx and the initiation of action potential:
  • Opening of a few fast voltage-gated Na+ channels allows extracellular Na+ entry, initiating the rising phase; Na+ channels quickly inactivate.

Page 88

• Phase details (continued):
  • Phase 0 depolarization duration ~3–5 ms.

Page 89

• Plateau phase details:
  • Prolonged plateau due to Ca2+ influx and limited K+ efflux; keeps cell depolarized and allows sustained contraction.
  • Plateau lasts ~$175\text{ ms}$.

Page 90

• Calcium-driven plateau:
  • Slow Ca2+ channels open; Ca2+ enters; few K+ channels open; plateau prolongs.
  • Calcium release maintains contraction; contraction continues as long as Ca2+ is entering.

Page 91

• Plateau consequences:
  • Plateau sustains contraction to ensure emptying of ventricles into the aorta and pulmonary trunk.

Page 92

• Repolarization mechanics (phase 3):
  • Ca2+ channels inactivate; K+ channels open; K+ efflux restores resting potential.
  • Ca2+ is pumped back into the sarcoplasmic reticulum and extracellular space.

Page 93

• Repolarization timing:
  • Repolarization lasts ~$75\text{ ms}$; complete return to resting potential.
  • Entire cycle length: roughly $250-300\text{ ms}$.

Page 94

• Absolute and relative refractory periods:
  • Absolute refractory period ≈ $200\text{ ms}$.
  • Relative refractory period ≈ $50\text{ ms}$.
  • Longer refractory prevents premature contractions and tetany during pumping.

Page 95

• Comparison with skeletal muscle AP/contraction:
  • Cardiac contractile AP lasts ~$200\text{ ms}$ (skeletal ~1-2 ms).
  • Cardiac contraction lasts ~$250-300\text{ ms}$ (skeletal ~15-100 ms).
  • Benefit: longer AP and contraction prevent tetanus and support sustained ejection of blood.

Page 96

• Skeletal vs cardiac contractile cell metrics (summary):
  • AP duration: skeletal ~1–2 ms vs cardiac ~200 ms.
  • Contraction duration: skeletal ~15–100 ms vs cardiac ~250–300 ms.

Page 97

• Electrocardiography (ECG) basics – waves and intervals (schematic):
  • Standard ECG shows P wave, QRS complex, and T wave.
  • These reflect atrial depolarization, ventricular depolarization, and ventricular repolarization respectively, along with associated intervals.

Page 98

• 12-lead ECG basics:
  • Electrodes form bipolar leads (between arms/around body) and unipolar leads (multiple sites).
  • Combined 12 leads provide a comprehensive view of electrical activity.

Page 99

• ECG as a comprehensive electrical record:
  • P, QRS, T waves; each point corresponds to activity at a particular heart region.

Page 100

• P wave and PR interval:
  • P wave lasts ~0.08 s; atrial depolarization from SA node leads to atrial contraction ~0.1 s after P wave onset.
  • PR interval: time from the start of atrial excitation to the start of ventricular excitation.

Page 101

• Diagrammatic interpretation of ECG waves (P, QRS, T interplay):
  • Atrial depolarization (P wave) triggers atrial systole.
  • After atrial depolarization, AV node delay occurs; QRS reflects ventricular depolarization.
  • Ventricular repolarization occurs during the T wave.

Page 102

• QRS complex details:
  • Large QRS complex represents ventricular depolarization and atrial repolarization (hidden within the complex).
  • Ventricles require a stronger electrical signal due to larger mass; contraction begins as the R wave peaks.

Page 103

• Ventricular depolarization and atrial repolarization:
  • Depolarization begins at the apex and spreads upward; atrial repolarization occurs during this interval but is masked by the dominant ventricular activity.

Page 104

• T wave and QT interval:
  • T wave represents ventricular repolarization.
  • QT interval spans from the start of ventricular depolarization to the end of ventricular repolarization.

Page 105

• Ventricular events continued:
  • Ventricular repolarization begins at the apex, producing the T wave.
  • QRS complex and T wave timing relationships are critical for diagnosing conduction abnormalities.

Page 106

• ST segment, PR segment, and TP segment definitions:
  • ST segment: period of complete ventricular depolarization.
  • PR segment: delay between atrial repolarization and ventricular depolarization (AV node delay).
  • TP segment: period of complete depolarization of the heart; no electrical activity measured.

Page 107

• ECG main features (visual reference):
  • Diagrammatic labeling (author credit).

Page 108

• Additional ECG labeling cues (schematic).

Page 109

• Cardiac cycle overview:
  • Definition: period from atrial contraction start to ventricular relaxation end.
  • Systole: contraction phase during which blood is pumped into circulation.
  • Diastole: relaxation phase during which chambers fill with blood.
  • Both atria and ventricles undergo systole and diastole; atria and ventricles cannot be in systole simultaneously.

Page 110

• Cardiac cycle phases overview:
  • Begins with atrial systole, progresses to ventricular systole, then atrial diastole, then ventricular diastole, then repeats.
  • Three major steps: 1) Ventricular filling, 2) Ventricular systole, 3) Isovolumic relaxation.

Page 111

• Cardiac cycle – Ventricular filling:
  • Both atria and ventricles in diastole; blood passively flows into atria; AV valves open; ventricles begin filling.
  • P wave triggers atrial contraction to push remaining blood into ventricles; ventricles start depolarizing (QRS).

Page 112

• Cardiac cycle – Ventricular systole (Phase A, isovolumetric):
  • Atria in diastole; ventricles depolarize; ventricles begin systole.
  • AV valves closed; insufficient pressure to open semilunar valves → isovolumetric contraction.

Page 113

• Cardiac cycle – Ventricular systole (Phase B, ejection):
  • Continued contraction increases pressure, opens SL valves; blood ejected from ventricles.
  • End-systolic volume (ESV) remains in ventricles after ejection.

Page 114

• Cardiac cycle – Isovolumic relaxation:
  • Atria and ventricles in diastole; ventricles repolarize and relax; SL valves closed due to backpressure; AV valves closed.
  • As atrial pressure rises, AV valves open and cycle restarts.

Page 115

• Relationship between cardiac cycle and ECG (phase-to-EKG mapping):
  • Initially both chambers in diastole; P wave corresponds to atrial depolarization followed by atrial systole.

Page 116

• Continued ECG-cycle relationship:
  • Atrial systole extends until QRS; ventricles depolarize and contract; T wave marks ventricular repolarization and onset of ventricular relaxation.

Page 117

• Cardiac cycle phase mapping (Vigorous diagram):
  • Phase notated as 1 (Atrial systole), 2A/2B (isovolumic contraction/early systole), 3 (ejection), etc. (Wiggers diagram integration).

Page 118

• Cardiac cycle – Volume and pressure snapshots (Wiggers diagram):
  • Visual data: ventricular volume changes from around 130 mL (EDV) down to ~ESV during ejection; isovolumic phases show no volume change.
  • Atrial and ventricular pressures plotted to show valve opening/closing moments alongside ECG.

Page 119

• Heart sounds (S1/S2):
  • S1: closure of AV valves during ventricular contraction; described as a "lub".
  • S2: closure of semilunar valves during ventricular diastole; described as a "dub".
  • Silence between S1 and S2 indicates relaxation.
  • Sequence: Mitral valve closes before the tricuspid; aortic valve closes before the pulmonary valve.

Page 120

• Heart sounds – auscultation details:
  • Each valve can be heard separately at different auscultation positions.

Page 121

• Cardiac Output (CO):
  • Definition: amount of blood pumped by each ventricle in one minute.
  • Formula: $CO = HR imes SV$ where $HR$ is heart rate (beats per minute) and $SV$ is stroke volume (volume per beat).
  • Normal value: $CO ext{ ≈ } 5.25 ext{ L/min}$.
• CO can be influenced by multiple factors (to be elaborated below).

Page 122

• Factors affecting heart rate and stroke volume:
  • Heart rate (HR): Autonomic innervation, hormones, fitness level, age.
  • Stroke volume (SV): Heart size, fitness, gender, contractility, duration of contraction, preload (EDV), afterload (systemic resistance).
• Key SV relation: $SV = EDV - ESV$ and $CO = HR imes SV$.

Page 123

• Questions to consider – ECG and cardiac cycle correlation (concept-check prompts):
  • Examples include locating phases of atrial systole, ventricular systole, AV and SL valve timings on the ECG, and identifying what happens when SL or AV valves are open/closed during various phases.

Page 124

• Further questions for self-review (advanced comprehension):

  • What might cause abnormalities in P wave, T wave, or QRS complex on ECG?
  • If SL valves are open, what is the status of the ventricles? If AV valves are open? If AV valves are closed? If SL valves are closed?
  • Identify the cardiac cycle phase corresponding to when SL valves are open or AV valves are open.
  • Review of how to map these states to phases like ventricular filling, isovolumic contraction, ejection, and isovolumic relaxation.

• End of content summary and exam-oriented prompts.