Chapter_19_Cardiovascular_System_

Page 2

General Function

• Cardiovascular System: Comprises the heart and blood vessels.

• Primary Functions:

  • Transports blood throughout the body.

  • Delivers oxygen (O2) and nutrients; removes carbon dioxide (CO2) and wastes.

• Adequate Perfusion:

  • Definition: Delivery of blood per time per gram of tissue (mL/min/g).

  • Importance: Maintains cell health.

  • Requires continuous pumping by the heart and healthy vessels.

Page 3

Overview of Components 1

• Blood Vessels:

  • Arteries: Carry blood away from the heart (most carry oxygenated blood).

  • Veins: Carry blood back to the heart (most carry deoxygenated blood).

  • Capillaries: Sites of gas exchange between blood and air in lungs or blood and body cells.

Page 4

The Cardiovascular System

• Figure 19.1 (image reference).

Page 5

Overview of Components 2

• Two Sides of the Heart:

  • Right Side: Receives deoxygenated blood, pumps it to lungs.

  • Left Side: Receives oxygenated blood, pumps it to the body.

• Heart Chambers:

  • Atria: Superior chambers that receive blood and send it to ventricles.

  • Ventricles: Inferior chambers that pump blood away.

Page 6

Overview of Components 3

• Great Vessels:

  • Superior and Inferior Vena Cava: Drain deoxygenated blood to right atrium.

  • Pulmonary Trunk: Transports blood from right ventricle; splits into pulmonary arteries.

  • Pulmonary Veins: Drain oxygenated blood into left atrium.

  • Aorta: Transports blood from left ventricle.

Page 7

Overview of Components 4

• Heart Valves:

  • Ensure one-way blood flow within the heart.

  • Types:

    • Atrioventricular (AV) Valves:

      • Between atrium and ventricle of each side.

      • Right AV (Tricuspid) and Left AV (Bicuspid or Mitral).

    • Semilunar Valves:

      • At boundary of ventricle and arterial trunk.

      • Pulmonary Semilunar Valve: Between right ventricle and pulmonary trunk.

      • Aortic Semilunar Valve: Between left ventricle and aorta.

Page 8

Pulmonary and Systemic Circulation

• Pulmonary Circulation:

  • Carries deoxygenated blood from right side of heart to lungs.

  • At lungs, blood picks up oxygen and releases carbon dioxide, returns to left side of heart.

• Systemic Circulation:

  • Carries oxygenated blood from left side of heart to body.

  • At systemic cells (e.g., skin, muscles), blood exchanges gases, nutrients, wastes, returns to right side of heart.

• Basic Pattern: Right heart → lungs → left heart → systemic tissues → right heart.

Page 9

Two Sides of the Heart

• Visual representation of the two sides of the heart.

Page 10

Clinical View: Congestive Heart Failure

• Definition: Impaired ability of the heart to pump blood.

• Symptoms:

  • Edema (Swelling):

    • Systemic Edema: Occurs if right ventricle is impaired; blood remains in systemic circulation, fluid enters interstitial space.

    • Pulmonary Edema: Occurs if left ventricle is impaired; blood remains in pulmonary circulation, swelling & fluid in lungs, causing difficulty breathing and impaired gas exchange.

Page 11

Location and Position of the Heart

• Enclosure: Heart is enclosed in pericardium within thoracic cavity.

• Position:

  • Posterior to sternum, to the left of body midline, between lungs in mediastinum.

  • Slightly rotated (right side more anterior).

• Anatomical Features:

  • Base: Postero-superior surface.

  • Apex: Inferior, conical end, projects slightly anteroinferiorly toward left side of body.

Page 12

Heart Position Within Thoracic Cavity

• Figure 19.4a (image reference).

Page 13

The Pericardium 1

• Structure: Heart is enclosed in three layers (the pericardium):

  • Fibrous Pericardium: Outermost covering, dense irregular connective tissue; anchors heart, prevents overfilling.

  • Parietal Layer of Serous Pericardium: Simple squamous epithelium and areolar connective tissue; attaches to fibrous pericardium.

  • Visceral Layer of Serous Pericardium: Simple squamous epithelium and areolar connective tissue attatched directly to the heart.

• Connection: Two serous layers are continuous and separated by the pericardial cavity.

Page 14

The Pericardium 2

• Fluid: Pericardial cavity contains serous fluid that acts as a lubricant.

• Structure: Fibrous pericardium and parietal layer together form the pericardial sac.

Page 15

Layers of the Heart Wall

• Three Layers:

  • Epicardium: Outermost layer; simple squamous epithelium and areolar connective tissue.

  • Myocardium: Middle and thickest layer; composed of cardiac muscle tissue; contracts to pump blood.

  • Endocardium: Covers internal surface of heart and external surface of valves; simple squamous epithelium and areolar connective tissue; continuous with lining of blood vessels.

Page 16

Layers of the Heart Wall 1

• Variations in Thickness:

  • Ventricles (pumping chambers) have thicker walls than atria.

  • Left ventricle has thicker wall than right ventricle to generate higher pressure for systemic circulation, while the right ventricle pumps to nearby lungs.

Page 17

Pericardium

• Figure 19.5 (image reference).

Page 18

External Anatomy and Features of the Heart: Anterior View

• Figure 19.6a (image reference).

Page 19

Internal Anatomy of the Heart

• Internal representation of the heart.

Page 20

Heart Chambers 1

• Separation of Chambers:

  • Interatrial Septum: Separates left atrium from right atrium.

  • Interventricular Septum: Separates left ventricle from right ventricle.

• Right Atrium:

  • Contains pectinate muscles (ridges) and fossa ovalis (oval depression on interatrial septum, fetal remnant).

  • Enters from coronary sinus, superior vena cava, inferior vena cava; exits to right ventricle through right AV valve.

Page 21

Heart Chambers 2

• Right Ventricle:

  • Contains trabeculae carneae (irregular muscular ridges) and papillary muscles (cone-shaped projections).

  • Papillary muscles anchor chordae tendineae.

  • Exits to pulmonary trunk through pulmonary semilunar valve.

Page 22

Heart Chambers 3

• Left Atrium:

  • Contains pectinate muscles in its auricle.

  • Enters from pulmonary veins.

  • Exits to left ventricle through left AV valve.

• Left Ventricle:

  • Contains trabeculae carneae on internal wall surface; two papillary muscles anchor chordae tendineae.

  • Exits to aorta through aortic semilunar valve.

Page 23

Heart Valves

• Function: Ensure one-way blood flow.

• Types:

  • Atrioventricular Valves:

    • Prevent backflow into atria.

    • Right AV (Tricuspid) valve and Left AV (Mitral/Bicuspid) valve.

    • Close when ventricles contract, forcing blood upward.

  • Papillary Muscles and Chordae Tendineae: Prevent inversion into atria.

Page 24

Heart Valves 2

• Semilunar Valves:

  • Prevent backflow into ventricles.

  • Open during ventricular contraction; close during relaxation (arterial pressure > ventricular pressure).

  • Each has three cusps.

  • Pulmonary Semilunar Valve: Between right ventricle and pulmonary trunk.

  • Aortic Semilunar Valve: Between left ventricle and aorta.

Page 25

Superficial Features of the Heart 1

• Anterior View:

  • Prominent right atrium and right ventricle.

  • Notable right auricle.

  • Left auricle and portions of left ventricle visible.

  • Great Vessels: Pulmonary trunk, ascending aorta, aortic arch, descending aorta.

Page 26

Heart Valves: Mechanism of Action

• Mechanisms by which heart valves ensure proper blood flow (img reference).

Page 27

Clinical View: Pericarditis

• Definition: Inflammation of the pericardium, caused by infections.

• Symptoms:

  • Increased capillary permeability, leading to fluid accumulation in pericardial cavity.

  • Can restrict heart movement and fill chambers, resulting in cardiac tamponade.

  • Sound: Friction rub heard as pericardial layers rub against each other.

Page 28

Clinical View: Cardiomegaly and Hypertrophic Cardiomyopathy

• Cardiomegaly: Enlargement of heart due to various causes (most often high blood pressure or coronary heart disease).

• Effects: Enlargement leads to reduced contractility, possibly resulting in congestive heart failure.

• Hypertrophic Cardiomyopathy: Thickening of heart walls, narrowing openings for blood, reducing output; confirmed by ultrasound.

Page 29

Clinical View: Heart Sounds and Heart Murmurs 1

• Normal Heart Sounds: S1 (closing of AV valves) and S2 (closing of semilunar valves); S3 and S4 are clinically useful sounds.

• Heart Murmur: Abnormal sound from turbulence during blood flow.

• Types: Valvular insufficiency and valvular stenosis.

Page 30

Clinical View: Heart Sounds and Heart Murmurs 2

• Valvular Insufficiency: Leaking valves due to incompletely closing cusps.

• Valvular Stenosis: Scarred valve cusps that restrict blood flow, leading to reduced chamber output.

Page 31

Coronary Vessels: Blood Supply Within the Heart Wall 1

• Coronary Circulation: Delivers blood to heart wall.

• Coronary Arteries: Supply oxygenated blood to heart.

• Coronary Veins: Return deoxygenated blood towards right atrium.

Page 32

Coronary Arteries

• Figure 19.11a (image reference).

Page 33

Clinical View: Coronary Heart Disease, Angina Pectoris, and Myocardial Infarction

• Coronary Heart Disease: Plaque buildup in coronary arteries (atherosclerosis) reduces blood flow.

• Coronary Spasm: Sudden narrowing of vessels.

• Angina Pectoris: Heart pain during exertion, treated with vasodilators.

• Myocardial Infarction: Heart attack; sudden occlusion of coronary artery; symptoms include chest pain, weakness, and shortness of breath.

Page 34

Microscopic Structure of Cardiac Muscle 1

• Composition: Cardiac muscle tissue; cells are short, branched, with one or two nuclei.

• Connective Tissue: Supported by areolar connective tissue called endomysium.

• Features: Sarcolemma (plasma membrane with T-tubules), sarcoplasmic reticulum surrounds myofilament bundles, creating striated appearance under the microscope.

• Optimal Length: Greater overlap of filaments occurs when the heart is stretched by blood filling the chamber, enabling stronger contractions.

Page 35

Microscopic Structure of Cardiac Muscle 2

• Intercellular Structures: Sarcolemma folded at connections increases stability and communication.

• Connections: Intercalated discs contain desmosomes (mechanical connections) and gap junctions (ionic connections for functional syncytium).

Page 36

Microscopic Structure of Cardiac Muscle 3

• Metabolism: High energy demand; extensive blood supply; numerous mitochondria, myoglobin, and creatine kinase.

• Metabolic Flexibility: Uses varied fuel molecules (fatty acids, glucose, etc.).

• Dependency: Relies mostly on aerobic metabolism; susceptible to ischemia can lead to cell death.

Page 37

The Heart’s Conduction System 1

• Definition: Initiates and conducts electrical events ensuring proper timing of contractions; influenced by the autonomic nervous system.

Page 38

Electrical Events at the SA Node: Initiation of the Action Potential 1

• SA Node Cells: Exhibit autorhythmicity.

• Process:

  • Threshold reached via slow voltage-gated Na+ channels; membrane potential rises.

  • Depolarization caused by fast voltage-gated Ca2+ channels opening.

  • Repolarization: closure of Ca2+ channels and opening of K+ channels restores resting potential.

Page 39

Conduction System of the Heart: Spread of the Action Potential 1

• Flow and Delay: Action potential spreads from SA node to atria and AV node; delay at AV node allows ventricles to fill.

• Pathway: SA node → AV node → AV bundle → Purkinje fibers; action potentials spread through ventricles for simultaneous contraction.

Page 40

Conduction System of the Heart: Spread of the Action Potential 2

• Special Features: Purkinje fibers are larger in diameter for rapid action potential distribution and ensure concurrent contraction, optimally pulling on chordae tendineae to maintain valve function during contraction.

Page 41

Electrical and Mechanical Events of Cardiac Muscle Cells 1

• Electrical Events:

  • Depolarization: Fast voltage-gated Na+ channels open; membrane potential increases rapidly.

  • Plateau: K+ and slow Ca2+ channels open, maintaining depolarization while stimulating further Ca2+ release from sarcoplasmic reticulum.

Page 42

[Empty Page]

Page 43

The Heart’s Conduction System 2

• Components:

  • SA Node: Pacemaker, located in right atrium.

  • AV Node: Located in floor of right atrium.

  • AV Bundle (Bundle of His): Extends from AV node.

  • Purkinje Fibers: Extend into ventricles, transmitting impulses.

Page 44

Conduction System

• Figure 19.13a (image reference).

Page 45

Innervation of the Heart 1

• Medulla Oblongata: Cardiac center containing cardioacceleratory and cardioinhibitory centers; receives signals from baroreceptors and chemoreceptors.

• Function: Modifies cardiac activity via sympathetic and parasympathetic pathways, adjusting heart rate and force of contraction.

Page 46

Innervation of the Heart 2

• Parasympathetic Innervation: Decreases heart rate (vagus nerves).

• Sympathetic Innervation: Increases heart rate and contraction force (T1-T5 spinal segments).

Page 47

Physiologic Processes Associated with Heart Contraction

• Figure 19.14a (image reference).

Page 48

SA Nodal Cells at Rest

• Function: Initiate heartbeat via spontaneous depolarization.

• Membrane Characteristics: Resting membrane potential (RMP) at -60mV, many membrane proteins present.

Page 49

[Empty Page]

Page 50

[Empty Page]

Page 51

[Empty Page]

Page 52

Bradycardia

• Definition: Heart beats slowly due to failure in conduction of electrical impulses.

Page 53

Ventricular Tachycardia

• Definition: Abnormal electrical signals in ventricle, up to 250 beats per minute.

• Concern: Regular rhythm, but atria contribute insufficiently to ventricular filling.

Page 54

Clinical View: Ectopic Pacemaker

• Definition: Pacemaker activity from cells other than SA node, can occur in AV node or muscle cells.

• Implications: Default AV node acts as pacemaker if SA node fails; fewer than 40 beats/min generally unsustainable for life.

Page 55

Cardiac Muscle Cells at Rest 1

• Characteristics:

  • Contains Na+/K+ and Ca2+ pumps, leakage channels; RMP of -90mV.

  • Specific voltage-gated channels present.

Page 56

Electrical and Mechanical Events of Cardiac Muscle Cells 2

• Repolarization: Voltage-gated Ca2+ channels close; membrane potential returns to -90mV.

Page 57

Electrical Events at the Sarcolemma of a Cardiac Muscle Cell

• Figure 19.19 (image reference).

Page 58

Electrical and Mechanical Events of Cardiac Muscle Cells 3

• Mechanical Events: Ca2+ entry triggers contraction via crossbridge cycling; contraction-relaxation sequence follows elevation and decline of calcium levels.

Page 59

Repolarization and the Refractory Period

• Refractory Period: Cardiac muscle cannot exhibit tetany; prolonged, around 250ms making sustained contraction impossible.

Page 60

Electrical and Mechanical Events in Skeletal Muscle Cells

• Figure 19.20a,b (image reference).

Page 61

Electrical and Mechanical Events in Cardiac Muscle Cells

• Figure 19.20c,d (image reference).

Page 62

Electrocardiogram (ECG) 1

• Definition: Diagnostic tool detecting electrical signals from cardiac muscle cells through skin electrodes.

• Waves:

  • P Wave: Atrial depolarization.

  • QRS Complex: Ventricular depolarization, concurrent atrial repolarization.

  • T Wave: Ventricular repolarization.

Page 63

Electrocardiogram (ECG) 2

• Segments:

  • P-Q Segment: Atrial plateau phase (contraction).

  • S-T Segment: Ventricular plateau phase (contraction).

Page 64

The Electrocardiogram 1

• Figure 19.21a (image reference).

Page 65

The Electrocardiogram 2

• Figure 19.21b (image reference).

Page 66

Electrocardiogram (ECG) 3

• Electrical Events:

  • Atrial activities recorded in different waves (P-Q-S-T) indicating depolarizations and repolarizations during the cycle.

Page 67

Electrical Events of the Heart and an ECG

• Figure 19.22 (image reference).

Page 68

Electrocardiogram (ECG) 4

• Intervals:

  • P-R Interval: Duration from atrial depolarization to ventricular depolarization, indicates conduction via the heart.

  • Q-T Interval: Reflects duration of ventricular action potentials which can vary with heart rate; importance in monitoring for arrhythmias.

Page 69

Clinical View: Cardiac Arrhythmia 1

• Definition: Any abnormality in heart's electrical activity.

• Heart Blocks:

  • First-degree: PR prolongation.

  • Second-degree: Some atrial action potentials fail to reach ventricles.

  • Third-degree: Complete failure of all action potentials reaching ventricles.

Page 70

Clinical View: Cardiac Arrhythmia 2

• Premature Ventricular Contractions: Caused by stress or stimulants; not harmful unless frequent.

• Atrial Fibrillation: Irregular atrial activity.

• Ventricular Fibrillation: Chaotic ventricular activity, life-threatening; requires defibrillation.

Page 71

Overview of the Cardiac Cycle 1

• Definition: Cardiac cycle refers to events from the start of one heartbeat to the next, includes systole (contraction) and diastole (relaxation).

• Pressure Dynamics: Contraction raises pressure, relaxation lowers it; blood moves down a pressure gradient.

Page 72

Overview of the Cardiac Cycle 2

• Ventricular Activities: Critical for blood ejection;

  • Ventricular contraction raises pressure, closing AV valves and opening semilunar valves to push blood into arteries.

  • Ventricular relaxation lowers pressure, closing semilunar valves, leading to AV valves opening for filling.

Page 73

Events of the Cardiac Cycle 1

• Resting Phase: Four chambers at rest, blood passively filling ventricles; AV valves open due to higher atrial pressure.

Page 74

Events of the Cardiac Cycle 2

• Atrial Contraction: Starts excitation from SA node; atria contract, filling ventricles to end-diastolic volume (EDV).

• Isovolumic Contraction: Ventricles contract, pushing AV valves closed while maintaining fixed blood volume within.

Page 75

Events of the Cardiac Cycle 3

• Ventricular Ejection: Ventricles contract enough to exceed arterial pressures, forcing semilunar valves open.

• Volume Calculations: Stroke volume is the amount ejected; end-systolic volume (ESV) remains post-contraction.

Page 76

Events of the Cardiac Cycle 4

• Isovolumic Relaxation: Ventricles relax; pressures fall below arterial pressures causing semilunar valves to close without blood movement.

Page 77

Events of the Cardiac Cycle 5

• Atrial Relaxation: All heart chambers relaxed; AV valves open, allowing blood to flow into ventricles.

Page 78

Phases of the Cardiac Cycle 1

• Figure 19.23a-c (image reference).

Page 79

Phases of the Cardiac Cycle 2

• Figure 19.23d-f (image reference).

Page 80

Events of the Cardiac Cycle 6

• Ventricular Balance: Equal volumes pumped by both sides; left side must work harder due to distance, maintaining ejection volumes.

Page 81

Introduction to Cardiac Output 1

• Definition: Amount of blood pumped by one ventricle in a minute; indicated in liters.

• Calculation: Cardiac Output (CO) = Heart Rate (HR) × Stroke Volume (SV).

Page 82

Introduction to Cardiac Output 2

• Resting Output: Must match tissue needs; smaller hearts compensate with higher rates, larger hearts with stronger strokes.

Page 83

Variables That Influence Heart Rate 1

• Chronotropic Agents: Alter heart rate through SA and AV node activity, often via the autonomic system or hormones.

• Positive Agents: Increase rate through sympathetic stimuli; norepinephrine and epinephrine involved.

Page 84

Variables That Influence Heart Rate 2

• Positive Agents (contd.):

  • Thyroid Hormone: Increases β1-adrenergic receptors.

  • Caffeine: Inhibits breakdown of cAMP.

  • Nicotine: Increases norepinephrine release.

  • Cocaine: Inhibits norepinephrine reuptake.

Page 85

Variables That Influence Heart Rate 3

• Negative Agents: Decrease heart rate; parasympathetic activity (ACh release slows nodal firing).

• Beta-Blockers: Medications that block EPI and NE effects.

Page 86

Variables That Influence Heart Rate 4

• Autonomic Reflexes: Baroreceptor and chemoreceptor signals to the cardiac center adjust output as needed.

• Atrial Reflex: Decreases heart strain from overfilling via increased atrial pressure signaling the heart to increase rate.

Page 87

Variables That Influence Stroke Volume 1

• Stroke Volume: Amount of blood ejected per heartbeat influenced by venous return and inotropic agents.

• Venous Return: Volume of blood returned, defining preload and ventricular filling effect.

Page 88

Clinical View: Bradycardia and Tachycardia

• Bradycardia: Persistent low heart rate (below 60 bpm); can be normal in athletes but abnormal due to conditions like hypothyroidism.

• Tachycardia: Persistently high heart rate (over 100 bpm); occurs in various medical conditions.