Cardiovascular System: The Heart Chapter 19 Lecture Notes

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Cardiovascular System The HeartChapter 19
Lecture Notes

• to accompany
• Anatomy and Physiology From Science to Life
• textbook by
• Gail Jenkins, Christopher Kemnitz, Gerard Tortora

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Chapter Overview

• 19.1 Location Anatomy
• 19.2 Heart Chambers
• 19.3 Heart Valves
• 19.4 Heart Functions
• 19.5 Cardiac Conduction System
• 19.6 ECG
• 19.7 Cardiac Cycle
• 19.8 Cardiac Output

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Essential Terms

• cardiology
• study of the cardiovascular system
• apex of heart
• bottom point of heart formed by ventricles
• base of heart
• formed by atria, broad superior surface
• ventricles
• muscular chambers of the heart that eject blood
• atria
• collecting chambers of the heart that contract to
  fill the ventricles

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Introduction

• heart beats about 100,000 times every day or
  about 35 million beats per year
• left side pumps to systemic circuit
• right side pumps to pulmonary circuit

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Concept 19.1Location Heart Anatomy
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Heart Anatomy

• size 12cm long, 9cm wide at broadest part (5 x
  3.5)
• average mass 250g (8 oz) in females
• average mass 300g (10 oz) in males
• rests on diaphragm
• near midline of thoracic cavity
• 2/3 of to left of midline
• in mediastinum
• between lungs
• base is directed posteriorly and to right
• apex

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PERICARDIUM

• fibrous pericardium
• dense, irregular connective tissue
• functions
• protect and anchor
• serous pericardium
• 2. parietal pericardium
• fused to the fibrous pericardium
• 3. visceral pericardium
• also called epicardium
• pericardial cavity of the serous pericardium is
  filled with pericardial fluid

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Heart Wall

• epicardium
• visceral layer of serous pericardium
• myocardium
• cardiac muscle
• involuntary
• branched cells
• intercalated discs
• gap junctions
• Desmosomes
• endocardium
• continuous through out cardiovascular system

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Concept 19.2Heart Chambers
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Right Atrium (RA)

• receives blood from
• superior vena cava
• inferior vena cava
• coronary sinus
• posterior wall is smooth
• anterior wall is rough with pectinate muscles
  that extend into auricle
• divided from left atrium by thin partition called
  interatrial septum
• oval depression in septum called fossa ovalis
• remnant of foramen ovale
• blood leaves RA through tricuspid valve

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Figure 19.4a
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Figure 19.4b
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Figure 19.4c
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Right Ventricle (RV)

• receives blood from right atrium
• forms most of the anterior surface of heart
• contains trabeaculae carneae
• raised bundles of cardiac muscle
• cusps of tricuspid valve connected to chordae
  tendineae
• chordae tendineae connected to cone-shaped
  trabeaculae carneae called papillary muscles
• divided from left ventricle by interventricular
  septum
• blood ejected to pulmonary valve to pulmonary
  trunk en route to lungs for gas exchange

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Figure 19.3a
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Figure 19.3b
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Figure 19.3c
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Left Atrium (LA)

• receives blood from lungs
• through 4 pulmonary veins
• structurally similar to right atrium
• blood passes to left ventricle through the
  bicuspid (mitral) valve

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Left Ventricle (LV)

• receives blood from LA
• through bicuspid valve
• internal structures similar to RV
• trabeaculae carneae
• chordae tendineae
• papillary muscles
• interventricular septum
• blood ejected into aorta
• some aortic blood travels to coronary arteries
• remainder passes to arch of aorta
• fetal life blood passes from pulmonary trunk to
  aorta (bypassing lungs) through ductus arteriosus
  (closes shortly after birth)

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Figure 19.4a
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Figure 19.4b
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Figure 19.4c
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Figure 19.1a
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Figure 19.1b
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Myocardium

• atrial walls are thinnest
• right ventricle thinner than left ventricle
• pumps blood shorter distance
• left ventricle walls thickest
• right and left ventricles pump same volume of
  blood with each beat

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Figure 19.4a
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Figure 19.4b
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Figure 19.4c
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Concept 19.3Heart Valves
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Valves Of The Heart

• Ensure one way flow through the heart
• Atrioventricular Valves
• between the atria the ventricles
• right side - tricuspid value
• left - bicuspid or mitral valve
• chordae tendineae to papillary muscles
• Semilunar Valves
• at the beginning of the arteries that leave the
  heart
• 3 cusps per valve
• pulmonary semilunar valve
• aortic semilunar valve

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Concept 19.4Circulation
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Systemic and Pulmonary Circulation

• systemic circulation
• left side of the heart
• receives from lungs
• pumps to aorta body tissues
• oxygenated blood
• pulmonary circulation
• right side of the heart
• receives blood from the body tissues (veins)
• pumps to pulmonary trunk lungs
• deoxygenated blood

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Figure 19.6
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Coronary Circulation

• functional blood supply of the heart
• arteries arise from base of aorta and encircle
  heart in atrioventricular groove
• Left coronary artery
• runs toward left side of heart
• divides into anterior interventricular artery
• supplies blood to interventricular septum and
  anterior walls of both ventricles
• Right coronary artery
• runs toward right side of heart
• divides into marginal artery and posterior
  interventriculary artery
• Marginal artery serves lateral myocardium of
  right side
• Other serves heart apex and posterior ventricular
  walls

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Figure 19.7a
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Figure 19.7b
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Figure 19.7c
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Coronary Veins

• AKA coronary sinus
• great cardiac vein (anterior)
• middle cardiac vein (posterior)
• small cardiac vein
• anterior cardiac veins

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Figure 19.7a
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Figure 19.7b
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Figure 19.7c
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Concept 19.5Cardiac Conduction
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Anatomy of Cardiac Conduction System

• excitation begins at SA node (100/min_
• arrives at AV node located in interatrial septum,
  is slowed down (75/min)
• AP flows to AV bundle
• then enters right and left bundle branches
  traveling upward
• final AP arrives at Purkinje fibers contracting
  ventricular myocardium from apex up ejecting
  blood through semilunar valves

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Figure 19.8
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CONDUCTION SYSTEM

• Sequence of excitation
• sinoatrial (SA) node - spreads to both atria
• 90 - 100 action potentials per minute
• atrioventricular (AV) node
• 40 -50 action potentials per minute
• atrioventricular (AV) bundle (bundle of His)
• 20-40 action potentials per minute
• right left bundle branches
• in the interventricular septum
• Purkinje fibers
• conduction myofibers

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Figure 10.17a
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Figure 10.17b
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Figure 10.17c
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Concept 19.6ElectrocardiogramECG or EKG
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Electrocardiography

• recording of AP transmission through the cardiac
  conduction system
• electrodes placed on body surface
• arms and legs and six positions on chest
• graphed as series of up and down waves produced
  during each heartbeat
• instrument called electrocardiograph
• produces 12 different tracings

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ECG Waves

• P wave
• atrial depolarization
• QRS complex
• ventricular depolarization
• onset of ventricular contraction
• T wave
• ventricular repolarization
• just before ventricles start to relax
• atrial repolarization usually not visible
• masked by larger QRS complex

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Figure 19.9
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ECG Waves Heart Activity

• Systole
• contraction
• Diastole
• relaxation

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Figure 19.10
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Concept 19.7Cardiac Cycle
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CARDIAC CYCLE

• All events associated with one heartbeat
• two atria contract (atrial systole)
• while two ventricles relax (ventricular diastole)
• two ventricles contract (ventricular systole)
• while two atria relax (atrial diastole)

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Pressure Volume Changes

• Resting heart rate - about 75 beats/min.
• each beat approximately 0.8 seconds
• 0.4 seconds relaxation period
• greatest variation in timing is here
• 0.1 seconds atria contract
• 0.3 seconds atria relax ventricles contract

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Figure 19.11
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Atrial Systole

• SA node depolarization
• causes atrial systole forcing blood through AV
  valves into ventricles
• Ventricles fill
• EDV measure just prior to ventricle contraction
• approximately 130mL

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Ventricular Systole

• ventricles contract as atria relax
• pushes blood against AV valves forcing them shut
• all valves shut for an instant
• when pressure in ventricles exceed pressure in
  arteries both SL valves open and blood is ejected
  from ventricles
• resting body volume of blood ejected is about
  70mL (just over half of EDV)
• ESV is about 60mL

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Relaxation Period

• ventricular repolarization
• T wave in ECG
• causes ventricular diastole
• ventricles relax
• chamber pressure drops
• blood flows from pulmonary trunk and aorta back
  toward ventricles SL valves close
• isovolmetric relaxation
• all four valves closed
• when ventricular pressure less than atrial
  pressure AV valves open ventricle fill
• occurs without atrial systole
• another cardiac cycle begins at atrial
  depolarization (P wave)

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Heart Sounds

• Auscultation
• act of listening to heart sounds
• Sound of heart valves closing
• four sounds but only two loud enough to hear by
  stethoscope (S1 and S2)
• S1 lubb long, booming sound AV valves closing
• S2 dupp short, sharp sound SL valves closing
• S3 blood turbulence during ventricular filling
• S4 blood turbulence during atrial systole

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Figure 19.12a
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Figure 19.12b
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Concept 19.8Cardiac Output
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Cardiac Output

• Cardiac output equals stroke volume times heart
  rate
• CO SV x HR
• difference between resting and maximal cardiac
  output is called cardiac reserve
• Stroke volume equals the amount of blood in
  ventricle during diastole (EDV) minus the amount
  of blood in ventricle after it has contracted
  (ESV)
• SV EDV - ESV

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Regulation of Stroke Volume

• Preload
• degree of stretch of ventricles before
  contracting
• Frank-Starling law of the heart
• the greater the stretch - the greater the
  contraction (within limits)
• stretch is due to blood in the ventricles at the
  end of diastole (EDV)

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Regulation of Stroke Volume

• Contractility
• forcefulness of contraction of individual fibers
• increased contractility (positive inotropic)
• direct consequence of greater Ca2 influx
• Glucagon, thyroxine, epinephrine
• decrease contractility (negative inotropic)
• acidosis
• rising extracellular potassium
• calcium channel blockers
• Afterload
• pressure that must be exceeded before ejection
  begins
• pressure at semilunar valves of large arteries

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Control of Heart Rate

• cardiovascular center of medulla oblongata
• sensory inputs
• movement as monitored by proprioceptors increase
  input to cardiovascular center
• chemical changes in the blood, monitored by
  chemoreceptors
• blood pressure changes , monitored by
  baroreceptors

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Control of Heart Rate

• sympathetic effect
• cardiac accelerator nerves
• Release of NOR that bind to beta 1 receptors
• increases spontaneous firing of SA AV nodes
• increases Ca to contractile fibers
• parasympathetic effect
• vagus nerve
• Release of acetylecholine
• causes hyperpolarization (open K channels)
• slows spontaneous depolarization of intrinsic
  fibers
• PNS activation may be persistent in some grief
  and depression conditions

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Chemical Regulation of Heart Rate

• Hormonal effects
• EPI NOR, and thyroid hormones
• all increase heart activity
• Cations
• Na
• high levels block Ca2 inflow
• K
• high levels block AP generation
• Ca2
• high blood levels increase heart rate and
  activity
• low levels depress heart activity

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Other Factors

• Resting Heart rate influenced by
• age
• gender
• physical fitness
• bradycardia may be exhibited
• strong effective slow beats under 60bpm
• body temperature
• increased temperature increases rate
• decreased temperature decreases rate

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End Chapter 19