Download Heart, Pt. 2

Anatomy & Physiology
SIXTH EDITION
Chapter 20, part 3
The Heart
PowerPoint® Lecture Slide Presentation prepared by
Dr. Kathleen A. Ireland, Biology Instructor, Seabury Hall, Maui, Hawaii
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Frederic H. Martini
Fundamentals of
Contractile Cells
• Resting membrane potential of approximately –
90mV
• Action potential
• Rapid depolarization
• A plateau phase unique to cardiac muscle
• Repolarization
• Refractory period follows the action potential
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Calcium Ion and Cardiac contraction
• Cardiac action potentials cause an increase in
Ca2+ around myofibrils
• Ca2+ enters the cell membranes during the
plateau phase
• Additional Ca2+ is released from reserves in the
sarcoplasmic reticulum
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Figure 20.15 The Action Potential in Skeletal
and Cardiac Muscle
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Figure 20.15
Figure 20.15 The Action Potential in Skeletal
and Cardiac Muscle
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Figure 20.15
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
PLAY
Animation: Intrinsic Conduction System
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Figure 20.16 Phases of the Cardiac Cycle
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Figure 20.16
Figure 20.16 Phases of the Cardiac Cycle
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Figure 20.16
Pressure and volume changes: atrial systole
• rising atrial pressure pushes blood into the
ventricle
• atrial systole
• the end-diastolic volume (EDV) of blood is in the
ventricles
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Pressure and volume changes: ventricular systole
• Isovolumetric contraction of the ventricles:
ventricles are contracting but there is no blood
flow
• Ventricular pressure increases forcing blood
through the semilunar valves
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Pressure and volume changes: ventricular
diastole
• The period of isovolumetric relaxation when all
heart valves are closed
• Atrial pressure forces the AV valves open
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Figure 20.17 Pressure and Volume Relationships
in the Cardiac Cycle
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Figure 20.17
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
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Figure 20.18 Heart Sounds
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Figure 20.18a, b
SECTION 20-4
Cardiodynamics
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Stroke Volume and Cardiac Output
• Cardiac output – the amount of blood pumped by
each ventricle in one minute
• Cardiac output equals heart rate times stroke
volume
CO
HR
Cardiac output
Heart rate
(ml/min)
=
(beats/min)
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SV
X
Stroke
volume
(ml/beat)
Figure 20.19 A Simple Model of Stroke Volume
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Figure 20.19a-d
Factors Affecting Heart Rate
• Autonomic innervation
• Cardiac reflexes
• Tone
• SA node
• Hormones
• Epinephrine (E), norepinephrine(NE), and
thyroid hormone (T3)
• Venous return
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Figure 20.20 Factors Affecting Cardiac Output
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Figure 20.20
Medulla Oblongata centers affect autonomic
innervation
• Cardioacceleratory center activates sympathetic
neurons
• Cardioinhibitory center controls parasympathetic
neurons
• Receives input from higher centers, monitoring
blood pressure and dissolved gas concentrations
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Figure 20.21 Autonomic Innervation of the Heart
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Figure 20.21
Figure 20.21 Autonomic Innervation of the Heart
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Figure 20.21
Basic heart rate established by pacemaker cells
• SA node establishes baseline
• Modified by ANS
• Atrial reflex
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Figure 20.22 Pacemaker Function
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Figure 20.22
Figure 20.22 Pacemaker Function
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Figure 20.22
Factors Affecting stoke volume
• EDV
• Frank-Starling principle
• ESV
• Preload
• Contractility
• Afterload
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Figure 20.23 Factors Affecting Stroke Volume
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Figure 20.23
Figure 20.23 Factors Affecting Stroke Volume
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Figure 20.23
Autonomic Activity
• Sympathetic stimulation
• Positive inotropic effect
• Releases NE
• Parasympathetic stimulation
• Negative inotropic effect
• Releases ACh
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Exercise and Cardiac Output
• Heavy exercise can increase output by 300-500
percent
• Trained athletes may increase cardiac output
by 700 percent
• Cardiac reserve
• The difference between resting and maximal
cardiac output
PLAY
Animation: Cardiac cycle
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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
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Figure 20.24 A Summary of the Factors
Affecting Cardiac Output
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Figure 20.24
SECTION 20-5
The Heart and the Cardiovascular System
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The heart is part of the cardiovascular system
• The goal of the cardiovascular system is to
maintain adequate blood flow to all body tissues
• The heart works in conjunction with
cardiovascular centers and peripheral blood
vessels to achieve this goal
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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.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
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.
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings