Lecture 20, The Heart - Websupport1

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Anatomy & Physiology
SIXTH EDITION
Lecture 20, The Heart
Lecturer: Dr. Ebadi
Room P313
Phone: (718) 260-5285
E-Mail: [email protected]
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Frederic H. Martini
Fundamentals of
Learning Objectives
• Describe the organization of the cardiovascular
system.
• Describe the location and general features of the
heart, including the pericardium.
• Discuss the differences between nodal cells and
conducting cells and describe the components and
functions of the conducting system of the heart.
• Identify the electrical events associated with a
normal electrocardiogram.
Learning Objectives
• Explain the events of the cardiac cycle including
atrial and ventricular systole and diastole, and
relate the heart sounds to specific events in the
cycle.
• Define cardiac output, heart rate and stroke
volume and describe the factors that influence
these variables.
• Explain how adjustments in stroke volume and
cardiac output are coordinated at different levels
of activity.
The cardiovascular system is divided into two
circuits
• Pulmonary circuit
• Delivers blood from the right ventricle of the
heart to the lungs and from the lungs to the left
atrium of the heart
• System circuit
• Delivers blood from the left ventricle of the
heart to the rest of the body and collects blood
from the rest of the body and delivers it to the
right atrium of the heart.
An Overview of the Cardiovascular System
• Pulmonary circuit:
•
• System circuit
Anatomy of the Heart
The pericardia
• Visceral pericardium or epicardium
• Parietal pericardium
• Pericardial fluid
The Location of the Heart in the Thoracic Cavity
Superficial Anatomy of the Heart
• The heart consists of four chambers
• Two upper chamber called atria
• Two lower chambers called ventricles
• The two upper and two lower chambers are
separated by atrioventricular valve
The Superficial Anatomy of the Heart
The Heart Wall
• The heart wall is composed of three layers:
• Epicardium is primarily composed of Areolar
Tissue and epithelium
• Myocardium is primarily composed of cardiac
muscle tissue
• Endocardium is primarily composed of Areolar
Tissue and endothelium
The Heart Wall
Internal Anatomy and Organization
• Right Atrium
• Thin walled chambers that receive blood from superior
and inferior vena cava and pumps blood to the right
ventricle
• Left Atrium
• Thin walled chambers that receive blood from
pulmonary veins and pumps blood to left ventricle
• Right Ventricle
• Thick walled chamber that receives blood from right
atrium and pumps blood to pulmonary artery.
• Left Ventricle
• Thick walled chamber that receives blood from left
atrium and pumps blood to the Aorta.
Internal Anatomy and Organization
• The two ventricles are separated from the atria by
atrioventricular (AV) valves
• Tricuspid valve separates right atrium from right
ventricle
• Bicuspid valve separates left atrium from left ventricle
• Chordae tendineae
• Tendinous fibers attached to the cusps of AV valves
• It attaches the cusps of atrioventricular valves to
papillary muscles
• It prevents the AV valve from reversing into the atria as
papillary muscles contract
• Papillary muscle and trabeculae carneae
• Muscular projections on the inner wall of ventricles
Blood flow through the heart
• Right atria –receives blood from superior and
inferior vena cava and pumps it to the right
ventricle through the tricuspid valve
• Right ventricle –receives blood from right atrium
and pumps it toto the pulmonary artery through
the pulmonary semilunar valve
• Pulmonary artery -delivers the blood to the lungs
• At the lungs gas exchange occur
• Oxygen diffuses from the alveoli to the
capillary and carbon dioxide diffuses from
the capillary to the alveoli.
Blood flow through the heart
• Pulmonary Vein - after the gas exchange at the
lungs pulmonary veins collect the blood and
delivers them to the left atrium.
• Left atria – receives blood from pulmonary veins
and pumps it to the left ventricle through the
bicuspid valve
• Left ventricle- receives blood from the left atria
and pumps it to the aorta through the aortic
semilunar valve
Blood flow through the heart
• Aorta branches into smaller arteries and delivers
the blood to the cells throughout the body.
• Gas exchange occur between the cell and the
capillaries
• Oxygen diffuses from the capillaries to the
cell and carbon dioxide diffuses from the cell
to the capillaries.
• After the gas exchange the blood is delivered
back to the heart by superior and inferior vena
cava.
The Sectional Anatomy of the Heart
Structural Differences in heart chambers and valves
• Compared to the right ventricle the left ventricle
is:
• More muscular and has thicker wall
• Develops higher pressure during contraction
• Produces about 6 times more force during contraction
• Round in cross section
• Functions of valves
• AV valves prevent backflow of blood from the ventricles
to the atria
• Semilunar valves prevent backflow of blood from the
pulmonary trunk and aorta to the ventricles.
Structural Differences between the Left and
Right Ventricles
Valves of the Heart
Connective Tissues
• Connective tissue fibers of the heart
• Provide physical support and elasticity
• Distribute the force of contraction
• Prevent overexpansion
Blood Supply to the Heart
• Coronary arteries are the first blood vessels to
branch from the aorta
• Coronary arteries supply blood to the heart and
coronary veins collect the blood from the heart
• Arteries include the right and left coronary
arteries, marginal arteries, anterior and
posterior interventricular arteries, and the
circumflex artery
• Veins include the great cardiac vein, anterior
and posterior cardiac veins, the middle cardiac
vein, and the small cardiac vein
Coronary Circulation
Coronary Circulation
The Heartbeat
Cardiac Physiology
• Two classes of cardiac muscle cells
• Specialized muscle cells of the conducting
system
• Contractile cells
An Overview of Cardiac Physiology
The Conducting System
• The conducting system includes:
• Sinoatrial (SA) node - Pacemaker cells are
located in the SA node
• Atrioventricular (AV) node
• AV bundle,
• bundle branches, and
• Purkinje fibers
Animation: Heart flythrough (see tutorial)
Impulse Conduction through the heart
• SA node begins the action potential
• Stimulus spreads to the AV node
• Impulse is delayed at AV node
• Impulse then travels through ventricular
conducting cells
• Then distributed by Purkinje fibers
Impulse Conduction through the Heart
Animation: Cardiac Activity (see tutorial)
The electrocardiogram (ECG)
• ECG is a recording of the electrical events
occurring during the cardiac cycle
• The P wave of ECG indicates the depolarization of the
atriums
• The QRS complex of ECG indicates the depolarization of
the ventricles
• The T wave of ECG indicates ventricular repolarization
• Analysis of ECG can reveal
• Condition of conducting system
• Effect of altered ion concentration
• Size of ventricles
• Position of the heart
An Electrocardiogram
Contractile Cells
• Resting membrane potential of approximately –
90mV
• Action potential
• Rapid depolarization
• A plateau phase unique to cardiac muscle
• Calcium channels remain open longer than
the sodium channels
• Repolarization
• Refractory period follows the action potential
The Action Potential in Skeletal and Cardiac
Muscle
The cardiac cycle
• The period between the start of one heartbeat
and the beginning of the next
• During a cardiac cycle
• Each heart chamber goes through systole and
diastole
• Correct pressure relationships are dependent
on careful timing of contractions
Animation: Intrinsic Conduction System (see tutorial)
Pressure and Volume Relationships in the
Cardiac Cycle
• See the video
that is posted
to the
blackboard to
understand
this graph
Heart sounds
• Auscultation – listening to heart sound via
stethoscope
• Four heart sounds
• S1 – “lubb” caused by the closing of the AV
valves
• S2 – “dupp” caused by the closing of the
semilunar valves
• S3 – a faint sound associated with blood
flowing into the ventricles
• S4 – another faint sound associated with atrial
contraction
Heart Sounds
Cardiodynamics
Stroke Volume and Cardiac Output
• Stroke volume - is the volume of blood ejected
with each ventricle contraction
• Cardiac output – is the amount of blood pumped
by each ventricle in one minute
• Cardiac output equals heart rate times stroke
volume
Medulla Oblongata centers affect autonomic
innervation
• Cardioacceleratory center activates sympathetic
neurons
• Cardioinhibitory center controls parasympathetic
neurons
• Medulla Oblongata centers receives input from
higher centers, monitoring blood pressure and
dissolved gas concentrations
Autonomic Innervation of the Heart
Autonomic Innervation of the Heart
Factors Affecting Stroke Volume
Factors Affecting Stroke Volume
Autonomic Activity
• Heart is innervated by sympathetic and
parasympathetic nerves.
• Sympathetic stimulation
• Positive inotropic effect
• Releases NE
• Parasympathetic stimulation
• Negative inotropic effect
• Releases ACh
Summary: Regulation of Heart Rate and Stroke
Volume
• Sympathetic stimulation increases heart rate
• Parasympathetic stimulation decreases heart rate
• Circulating hormones, specifically E, NE, and T3,
accelerate heart rate
• Increased venous return increases heart rate
• EDV is determined by available filling time and rate of
venous return
• ESV is determined by preload, degree of contractility, and
afterload
A Summary of the Factors Affecting Cardiac
Output
You should now be familiar with:
• The organization of the cardiovascular system.
• The location and general features of the heart,
including the pericardium.
• The differences between nodal cells and
conducting cells as well as the components and
functions of the conducting system of the heart.
• The electrical events associated with a normal
electrocardiogram.
You should now be familiar with:
• The events of the cardiac cycle including atrial
and ventricular systole and diastole, and the
heart sounds related to specific events in the
cycle.
• Cardiac output, heart rate and stroke volume and
the factors that influence these variables.
• How adjustments in stroke volume and cardiac
output are coordinated at different levels of
activity.
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