64
Oct-29-2013  A & P Fall-2013 Ch-20 The Heart Introduction to Anatomy and Physiology Chapter 20 Heart  1

A&P Ch-20 Oct-29-2013

Embed Size (px)

DESCRIPTION

Anatomy and Physiology Lecture

Citation preview

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    1/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    Introduction to Anatomy and Physiology

    Chapter 20Heart

    1

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    2/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    2

    Introduction to Cardiovascular System

    The Pulmonary Circuit Carries blood to and from gas exchange surfaces of lungs

    The Systemic Circuit

    Carries blood to and from the body

    Blood alternates between pulmonary circuit and systemic circuit

    Three Types of Blood Vessels1) Arteries : Carry blood away fromheart

    2) Veins : Carry blood toheart

    3) Capillaries : Networks betweenarteries andveins

    Also called exchange vessels

    Exchange materials between blood and tissues

    Materials include dissolved gases, nutrients, wastes

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    3/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    3

    Introduction to Cardiovascular System

    Figure 20

    1 An Overview of the Cardiovascular System.

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    4/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    4

    Anatomy of the Heart

    Figure 202a The Location of the Heart in the Thoracic Cavity

    Right atrium

    Collects blood fromsystemic circuit

    Right ventricle

    Pumps blood topulmonary circuit

    Left atrium

    Collects blood frompulmonary circuit

    Left ventricle

    Pumps blood tosystemic circuit

    Four Chambers of the Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    5/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    5

    Anatomy of the Heart

    Figure 20

    c2 The Location of the Heart in the Thoracic Cavity

    Parietal pericardium

    Visceral pericardium Pericardial cavity

    Pericardial sac

    The Pericardium

    Double lining of the pericardial cavity

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    6/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    6

    Anatomy of the Heart

    Figure 20

    3a The Superficial Anatomy of the Heart

    Atria

    Thin-walled

    Expandable outer auricle(atrial appendage)

    Sulci Coronary sulcus: divides

    atria and ventricles

    Anterior interventricularsulcusand posteriorinterventricular sulcus:

    separate left and rightventricles

    contain blood vessels ofcardiac muscle

    Superficial Anatomy of the Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    7/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    7

    Anatomy of the Heart

    Figure 204 The Heart Wall

    Epicardium(outer layer)

    Visceral pericardium

    Covers the heart

    Myocardium(middle layer)

    Muscular wall of the heart Concentric layers of cardiac

    muscle tissue

    Atrial myocardium wrapsaround great vessels

    Two divisions of ventricularmyocardium

    Endocardium(inner layer)

    Simple squamous epithelium

    The Heart Wall

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    8/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    8

    Anatomy of the Heart

    Figure 20

    5 Cardiac Muscle Cells

    Cardiac Muscle Tissue

    Small size

    Single, central nucleus

    Branching interconnections

    between cells

    Intercalated discs

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    9/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    9

    Anatomy of the Heart

    Figure 205 Cardiac Muscle Cells

    Interconnect cardiac muscle cells Secured by desmosomes

    Linked by gap junctions

    Convey force of contraction

    Propagate action potentials

    Intercalated discs

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    10/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    10

    Anatomy of the Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    11/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    11

    Anatomy of the Heart

    Internal Anatomy and Organization

    Interatrial septum: separates atria

    Interventricular septum: separates ventricles

    Atrioventricular (AV) valves

    Connect right atrium to right ventricle and left atrium to left

    ventricle

    The fibrous flaps that form bicuspid (2) and tricuspid (3) valves

    Permit blood flow in one direction: atria to ventricles

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    12/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    12

    Anatomy of the Heart

    The Right Atrium Superior vena cava

    Receives blood from head, neck, upper limbs, and chest

    Inferior vena cava

    Receives blood from trunk, viscera, and lower limbs

    Coronary sinus Cardiac veins return blood to coronary sinus

    Coronary sinus opens into right atrium

    Foramen ovale

    Before birth, is an opening through interatrial septum

    Connects the two atria Seals off at birth, forming fossa ovalis

    Pectinate muscles

    Contain prominent muscular ridges

    On anterior atrial wall and inner surfaces of right auricle

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    13/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    13

    Anatomy of the Heart

    Figure 20

    6a-b The Sectional Anatomy of the Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    14/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    14

    Anatomy of the Heart

    The Right Ventricle

    Free edges attach to chordae tendineaefrom papillarymusclesof ventricle

    Prevent valve from opening backward

    Right atrioventricular (AV) Valve

    Also called tricuspid valve Opening from right atrium to right ventricle

    Has three cusps

    Prevents backflow

    Trabeculae carneae

    Muscular ridges on internal surface of right (and left)ventricle

    Includes moderator band:

    ridge contains part of conducting system

    coordinates contractions of cardiac muscle cells

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    15/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    15

    Anatomy of the Heart

    The Pulmonary Circuit

    Conus arteriosus(superior end of right ventricle) leadsto pulmonary trunk

    Pulmonary trunk divides into left andright pulmonaryarteries

    Blood flows from right ventricle to pulmonary trunkthrough pulmonary valve

    Pulmonary valve has three semilunar cusps

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    16/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    16

    Anatomy of the Heart

    The Left Atrium

    Blood gathers into left andright pulmonary veins

    Pulmonary veins deliver to left atrium

    Blood from left atrium passes to left ventricle through leftatrioventricular (AV) valve

    A two-cuspedbicuspid valveor mitral valve

    The Left Ventricle Holds same volume as right ventricle

    Is larger; muscle is thicker and more powerful

    Similar internally to right ventricle but does nothave moderator band

    Systemic circulation

    Blood leaves left ventricle through aortic valveinto ascendingaorta

    Ascending aorta turns (aortic arch) and becomes descending

    aorta

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    17/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    17

    Anatomy of the Heart

    Structural Differencesbetween the Left and RightVentricles

    Right ventricle wall is thinner, develops less pressure than leftventricle

    Right ventricle is pouch-shaped, left ventricle is round

    Figure 207 Structural Differences between the Left and Right Ventricles

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    18/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    18

    Anatomy of the Heart

    The Heart Valves

    Two pairs of one-way valves prevent backflow during contraction Atrioventricular (AV) valves

    Between atria and ventricles

    Blood pressure closes valve cusps during ventricular contraction

    Papillary muscles tense chordae tendineae: prevent valves from swinging

    into atria Semilunar valves

    Pulmonary and aortic tricuspid valves

    Prevent backflow from pulmonary trunk and aorta into ventricles

    Have no muscular support

    Three cusps support like tripod

    Aortic Sinuses At base of ascending aorta

    Sacs that prevent valve cusps from sticking to aorta

    Origin of right and left coronary arteries

    h h

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    19/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    19

    Anatomy of the Heart

    Figure 208 Valves of the Heart

    OCh Th H

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    20/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    20

    Anatomy of the Heart

    Connective Tissues and the Cardiac (Fibrous) Skeleton Physically support cardiac muscle fibers

    Distribute forces of contraction

    Add strength and prevent overexpansion of heart

    Elastic fibers return heart to original shape after contraction

    The Cardiac (Fibrous) Skeleton

    Four bands around heart valves and bases of pulmonary trunkand aorta

    Stabilize valves

    Electrically insulate ventricular cells from atrial cells

    O tCh Th H t

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    21/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    21

    Anatomy of the Heart

    The Blood Supply to the Heart = Coronary Circulation

    Coronary arteriesand cardiac veins

    Supplies blood to muscle tissue of heart

    The Cardiac Veins

    Great cardiac vein Drains blood from area of

    anterior interventricular arteryinto coronary sinus

    Anterior cardiac veins

    Empties into right atrium Posterior cardiac vein,

    middle cardiac vein, andsmall cardiac vein

    Empty into great cardiac veinor coronary sinus

    The Coronary Arteries Left and right

    Originate at aortic sinuses

    High blood pressure, elasticrebound forces blood

    through coronary arteriesbetween contractions

    O t 29 2013Ch 20 Th H t

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    22/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    22

    Anatomy of the Heart

    2) Left Coronary Artery Supplies blood to

    Left ventricle

    Left atrium

    Interventricular septum

    Two main branches of leftcoronary artery Circumflex artery Anterior interventricular artery

    Arterial Anastomoses

    Interconnect anterior and posteriorinterventricular arteries

    Stabilize blood supply to cardiacmuscle

    1) Right Coronary Artery

    Supplies blood to

    Right atrium

    Portions of both ventricles

    Cells of sinoatrial (SA) andatrioventricular nodes

    Marginal arteries(surfaceof right ventricle)

    Posterior interventricularartery

    Oct 29 2013Ch 20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    23/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    23

    Anatomy of the Heart

    Figure 209a Coronary Circulation

    Oct 29 2013Ch 20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    24/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    24

    The Conducting System

    Heartbeat

    A single contraction of the heart

    The entire heart contracts in series

    First the atria

    Then the ventricles

    Two Types of Cardiac Muscle Cells Conducting system : Controls and coordinates heartbeat

    Contractile cells : Produce contractions that propel blood

    A system of specialized cardiac muscle cells

    Initiates and distributes electrical impulses that stimulatecontraction

    Automaticity

    Cardiac muscle tissue contracts automatically

    Oct 29 2013Ch 20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    25/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    25

    The Conducting System

    Figure 2011 An Overview of Cardiac Physiology

    The Cardiac Cycle Begins with action potential at

    SA node

    Transmitted throughconducting system

    Produces action potentials

    in cardiac muscle cells(contractile cells)

    Electrocardiogram (ECG)

    Electrical events in the

    cardiac cycle can be recordedon an electrocardiogram(ECG)

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    26/64

    Oct-29-2013

    A & P Fall-2013

    Ch-20 The Heart

    26

    The Conducting System

    Structures of the Conducting System

    Sinoatrial (SA) node - wall of right atrium

    Atrioventricular (AV) node - junction between atria and ventricles

    Conducting cells - throughout myocardium

    Conducting Cells

    Interconnect SA and AV nodes

    Distribute stimulus through myocardium

    In the atrium

    Internodal pathways

    In the ventricles

    AV bundle and the bundle branches

    Prepotential Also called pacemaker potential

    Resting potential of conducting cells

    Gradually depolarizes toward threshold

    SA node depolarizes first, establishing heart rate

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    27/64

    Oct 29 2013

    A & P Fall-2013

    Ch 20 The Heart

    27

    The Conducting System

    Figure 2012 The Conducting System of the Heart

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    28/64

    Oct 29 2013

    A & P Fall-2013

    Ch 20 The Heart

    28

    The Conducting System

    Figure 20

    13 Impulse Conduction through the Heart

    Heart Rate SA node generates

    80100 actionpotentials per minute

    Parasympathetic

    stimulation slowsheart rate

    AV node generates4060 actionpotentials per minute

    The Sinoatrial (SA) Node In posterior wall of right atrium

    Contains pacemaker cells

    Connected to AV node byinternodal pathways

    Begins atrial activation (Step 1)

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    29/64

    Oct 29 2013

    A & P Fall-2013

    Ch 20 The Heart

    29

    The Conducting System

    Figure 2013 Impulse Conduction through the Heart

    The Atrioventricular (AV) Node

    In floor of right atrium

    Receives impulse from SA node (Step 2)

    Delays impulse (Step 3)

    Atrial contraction begins

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    30/64

    9 3

    A & P Fall-201330

    The Conducting System

    Figure 20

    13 Impulse Conduction through the Heart

    The AV Bundle

    In the septum

    Carries impulse to left and right bundle branches

    Which conduct to Purkinje fibers (Step 4)

    And to the moderator band

    Which conducts to papillary muscles

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    31/64

    9 3

    A & P Fall-201331

    The Conducting System

    Figure 20

    13 Impulse Conduction through the Heart

    Purkinje Fibers Distribute impulse through ventricles (Step 5)

    Atrial contraction is completed

    Ventricular contraction begins

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    32/64

    9

    A & P Fall-201332

    The Conducting System

    Abnormal Pacemaker Function

    Bradycardia: abnormally slow heart rate

    Tachycardia: abnormally fast heart rate

    Ectopic pacemaker

    Abnormal cells

    Generate high rate of action potentials

    Bypass conducting system

    Disrupt ventricular contractions

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    33/64

    A & P Fall-201333

    The Conducting System

    A recording of electrical events in the heart

    Obtained by electrodes at specific body locations

    Abnormal patterns diagnose damage

    Electrocardiogram (ECG or EKG)

    Figure 2014b An Electrocardiogram: An ECG Printout

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    34/64

    A & P Fall-201334

    The Conducting System

    Features of an ECG

    P wave :Atria depolarize

    QRS complex :Ventricles depolarize

    T wave :Ventricles repolarize

    Time Intervals Between ECG Waves PR interval

    From start of atrial depolarization

    To start of QRS complex

    Q

    T interval From ventricular depolarization

    To ventricular repolarization

    Figure 2014a An Electrocardiogram: ElectrodePlacement for Recording a Standard ECG

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    35/64

    A & P Fall-201335

    The Conducting System

    Contractile Cells

    Purkinje fibers distribute the stimulus to the

    contractile cells, which make up most of themuscle cells in the heart

    Resting Potential

    Of a ventricular cell: about 90 mV

    Of an atrial cell: about

    80 mV

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    36/64

    A & P Fall-201336

    The Conducting System

    Figure 2015 The Action Potential in Skeletal and Cardiac Muscle

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    37/64

    A & P Fall-201337

    The Conducting System

    Figure 20

    15 The Action Potential in Skeletal and Cardiac Muscle

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    38/64

    A & P Fall-201338

    The Conducting System

    Refractory Period Absolute refractory period

    Long

    Cardiac muscle cells cannot respond

    Relative refractory period

    Short

    Response depends on degree of stimulus

    Timing of Refractory Periods

    Length of cardiac action potential in ventricular cell

    250

    300 msecs: 30 times longer than skeletal muscle fiber

    long refractory period prevents summation andtetany

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    39/64

    A & P Fall-201339

    The Conducting System

    The Role of Calcium Ions in Cardiac Contractions

    Contraction of a cardiac muscle cell is produced by anincrease in calcium ion concentration around myofibrils

    20% of calcium ions required for a contraction

    Calcium ions enter plasma membrane during plateau

    phase Arrival of extracellular Ca2+

    Triggers release of calcium ion reserves fromsarcoplasmic reticulum

    As slow calcium channelsclose

    Intracellular Ca2+is absorbed by the SR

    Or pumped out of cell

    Cardiac muscle tissue

    Very sensitive to extracellular Ca2+concentrations

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    40/64

    A & P Fall-201340

    The Conducting System

    The Energy for Cardiac Contractions

    Aerobic energy of heart

    From mitochondrial breakdown of fatty acids andglucose

    Oxygen from circulating hemoglobin

    Cardiac muscles store oxygen in myoglobin

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    41/64

    A & P Fall-201341

    The Cardiac Cycle

    Cardiac cycle = The period between the start of one

    heartbeat and the beginning of the next Includes both contraction and relaxation

    Phases of the Cardiac Cycle Within any one chamber

    Systole(contraction)

    Diastole(relaxation)

    Blood Pressure

    In any chamber

    Rises during systole

    Falls during diastole

    Blood flows from high to low pressure

    Controlled by timing of contractions

    Directed by one-way valves

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    42/64

    A & P Fall-201342

    The Cardiac Cycle

    Figure 20

    16 Phases of the Cardiac Cycle

    Oct-29-2013Ch-20 The Heart

    Th C di C l

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    43/64

    A & P Fall-201343

    The Cardiac Cycle

    Cardiac Cycle and Heart Rate

    At 75 beats per minute

    Cardiac cycle lasts about 800 msecs

    When heart rate increases

    All phases of cardiac cycle shorten, particularly diastole

    EightSteps in the Cardiac Cycle1. Atrial systole

    Atrial contraction begins

    Right and left AV valves are open

    2. Atria eject blood into ventricles

    Filling ventricles

    3. Atrial systole ends

    AV valves close

    Ventricles contain maximum blood volume

    Known as end-diastolic volume (EDV)

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    44/64

    A & P Fall-201344

    The Cardiac Cycle

    Figure 20

    17 Pressure and Volume Relationships in the Cardiac Cycle

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    45/64

    A & P Fall-201345

    The Cardiac Cycle

    Eight Steps in the Cardiac Cycle4. Ventricular systole

    Isovolumetric ventricular contraction

    Pressure in ventricles rises

    AV valves shut5. Ventricular ejection

    Semilunar valves open

    Blood flows into pulmonary and aortic trunks

    Stroke volume (SV) = 60% of end-diastolic volume

    6. Ventricular pressure falls Semilunar valves close

    Ventricles contain end-systolic volume (ESV), about 40% ofend-diastolic volume

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    46/64

    A & P Fall-201346

    The Cardiac Cycle

    Figure 2017 Pressure and Volume Relationships in the CardiacCycle

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    47/64

    A & P Fall-201347

    The Cardiac Cycle

    Eight Steps in the Cardiac Cycle7. Ventricular diastole

    Ventricular pressure is higher than atrial pressure

    All heart valves are closed

    Ventricles relax (isovolumetric relaxation)

    8. Atrial pressure is higher than ventricularpressure

    AV valves open

    Passive atrial filling

    Passive ventricular filling

    Cardiac cycle ends

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    48/64

    A & P Fall-201348

    The Cardiac Cycle

    Heart Sounds

    S1

    Loud sounds

    Produced by AV valves

    S2

    Loud sounds Produced by semilunar valves

    S3, S4

    Soft sounds

    Blood flow into ventricles and atrial contraction Heart Murmur

    Sounds produced by regurgitation through valves

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    49/64

    A & P Fall-201349

    The Cardiac Cycle

    Figure 2018 Heart Sounds

    Oct-29-2013Ch-20 The Heart

    C di d i

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    50/64

    A & P Fall-201350

    Cardiodynamics

    The movement and force generated by cardiac contractions

    End-diastolic volume (EDV)

    End-systolic volume (ESV)

    Stroke volume (SV)

    SV = EDV ESV

    Ejection fraction

    The percentage of EDV represented by SV Cardiac output (CO)

    The volume pumped by left ventricle in 1 minute

    Cardiac Output

    CO = HR X SV

    CO = cardiac output (mL/min)

    HR = heart rate (beats/min)

    SV = stroke volume (mL/beat)

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    51/64

    A & P Fall-201351

    Cardiodynamics

    Figure 2019 A Simple Model of Stroke Volume

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    52/64

    A & P Fall-201352

    Cardiodynamics

    Figure 2020 Factors Affecting Cardiac Output

    Cardiac output

    Adjusted by changes inheart rate or strokevolume

    Heart rate

    Adjusted by autonomicnervous system orhormones

    Stroke volume

    Adjusted by changingEDV or ESV

    Factors Affecting Cardiac Output

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    53/64

    A & P Fall-201353

    Cardiodynamics

    Factors Affecting the Heart Rate Autonomic innervation

    Cardiac plexuses: innervate heart

    Vagus nerves (X): carry parasympathetic preganglionic fibersto small ganglia in cardiac plexus

    Cardiac centers of medulla oblongata:

    cardioacceleratory centercontrols sympathetic

    neurons (increases heart rate)

    cardioinhibitory centercontrols parasympathetic

    neurons (slows heart rate)

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    54/64

    A & P Fall-201354

    Cardiodynamics

    Autonomic Innervation Cardiac reflexes

    Cardiac centers monitor:

    blood pressure (baroreceptors)

    arterial oxygen and carbon dioxide levels(chemoreceptors)

    Cardiac centers adjust cardiac activity

    Autonomic tone

    Dual innervation maintains resting tone byreleasing ACh and NE

    Fine adjustments meet needs of other systems

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    55/64

    A & P Fall-201355

    Cardiodynamics

    Figure 20

    21 Autonomic Innervation of the Heart

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    56/64

    A & P Fall-201356

    Cardiodynamics

    Effects on the SA Node

    Sympathetic andparasympathetic stimulation

    Greatest at SA node (heart rate)

    Membrane potential ofpacemaker cells

    Lower than other cardiac cells

    Rate of spontaneousdepolarization depends on

    Resting membrane potential

    Rate of depolarization

    ACh (parasympatheticstimulation)

    Slows the heart

    NE (sympathetic stimulation)

    Speeds the heart

    Atrial Reflex

    Also called Bainbridge reflex

    Adjusts heart rate in responseto venous return

    Stretch receptors in rightatrium

    Trigger increase in heart rate

    Through increasedsympathetic activity

    Increase heart rate (by sympatheticstimulation of SA node)

    Epinephrine (E)

    Norepinephrine (NE)

    Thyroid hormone

    Hormonal Effectson HR

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    57/64

    A & P Fall-201357

    Cardiodynamics

    Factors Affecting the Stroke Volume

    The EDV: amount of blood a ventricle contains at theend of diastole

    Filling time:

    duration of ventricular diastole

    Venous return:

    rate of blood flow during ventricular diastole

    Preload

    The degree of ventricular stretching during ventricular diastole Directly proportional to EDV

    Affects ability of muscle cells to produce tension

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    58/64

    A & P Fall-201358

    Cardiodynamics

    The EDV and Stroke Volume At rest

    EDV is low

    Myocardium stretches less

    Stroke volume is low

    With exercise

    EDV increases

    Myocardium stretches more

    Stroke volume increases

    The FrankStarling Principle

    As EDV increases, stroke volume increases

    Physical Limits Ventricular expansion is limited by

    Myocardial connective tissue

    The cardiac (fibrous) skeleton

    The pericardial sac

    Oct-29-2013Ch-20 The Heart

    C di d i

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    59/64

    A & P Fall-201359

    Cardiodynamics

    End-Systolic Volume (ESV) The amount of blood that remains in the

    ventricle at the end of ventricular systole isthe ESV

    Three Factors That Affect ESV Preload

    Ventricular stretching during diastole

    Contractility

    Force produced during contraction, at a given preload

    Afterload

    Tension the ventricle produces to open the semilunarvalve and eject blood

    Oct-29-2013Ch-20 The Heart

    C di d i

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    60/64

    A & P Fall-201360

    Cardiodynamics

    Contractility

    Is affected by

    Autonomic activity

    Hormones

    Effects of Autonomic Activity on Contractility

    Sympathetic stimulation

    NE released by postganglionic fibers of cardiacnerves

    Epinephrine and NE released by suprarenal(adrenal) medullae

    Causes ventricles to contract with more force

    Increases ejection fraction and decreases ESV

    Parasympathetic activity

    Acetylcholine released by vagus nerves

    Reduces force of cardiac contractions

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    61/64

    A & P Fall-201361

    Cardiodynamics

    Hormones

    Many hormones affect heart contraction

    Pharmaceutical drugs mimic hormone actions Stimulate or block beta receptors

    Affect calcium ions (e.g., calcium channel blockers)

    Afterload

    Is increased by any factor that restricts arterial blood flow

    As afterload increases, stroke volume decreases

    Oct-29-2013Ch-20 The Heart

    C di d i

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    62/64

    A & P Fall-201362

    Cardiodynamics

    Figure 20

    23 Factors Affecting Stroke Volume

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    63/64

    A & P Fall-201363

    Cardiodynamics

    Heart Rate Control Factors Autonomic nervous system

    Sympathetic andparasympathetic

    Circulating hormones

    Venous return and stretch receptors

    Stroke Volume Control Factors

    EDV

    Filling time

    Rate of venous return

    ESV

    Preload

    Contractility

    Afterload

    Oct-29-2013Ch-20 The Heart

  • 5/19/2018 A&P Ch-20 Oct-29-2013

    64/64

    Cardiodynamics

    Figure 2024 A Summary of the Factors Affecting Cardiac Output

    Cardiovascular regulation

    Ensures adequatecirculation to body tissues

    Cardiovascular centers Control heart and

    peripheral blood vessels

    Cardiovascular systemresponds to

    Changing activity patterns

    Circulatory emergencies

    The Heart and Cardiovascular System