Transcript Chapter 20: The Heart - Westerville City School District

Unit
4
Fluids and Transport
Fundamentals of
Anatomy & Physiology
Frederic H. Martini
PowerPoint® Lecture Slides prepared by
Professor Albia Dugger, Miami–Dade College, Miami, FL
Professor Robert R. Speed, Ph.D., Wallace Community College, Dothan, AL
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings
Chapter 20: The Heart
How are the cardiovascular
system and heart
organized?
Organization of the
Cardiovascular System
PLAY
The Heart: Anatomy
Figure 20–1
The Pulmonary Circuit
 Carries blood to and from gas
exchange surfaces of lungs
The Systemic Circuit
 Carries blood to and from the body
Alternating Circuits
 Blood alternates between pulmonary
circuit and systemic circuit
3 Types of Blood Vessels
 Arteries:
 carry blood away from heart
 Veins:
 carry blood to heart
 Capillaries:
 networks between arteries and veins
Capillaries
 Also called exchange vessels
 Exchange materials between blood
and tissues
 Dissolved gases, nutrients, wastes
4 Chambers of the Heart
 2 for each circuit:
 left and right:
 ventricles and atria
4 Chambers of the Heart
 Right atrium:
 collects blood from systemic circuit
 Right ventricle:
 pumps blood to pulmonary circuit
4 Chambers of the Heart
 Left atrium:
 collects blood from pulmonary circuit
 Left ventricle:
 pumps blood to systemic circuit
Where is the heart located
and what are its general
features?
Anatomy of the Heart
 Located directly behind sternum
PLAY
InterActive Physiology: Cardiovascular
System: Anatomy Review: The Heart
Figure 20–2a
Anatomy of the Heart
 Great veins and arteries at the base
 Pointed tip is apex
Figure 20–2c
Relation to Thoracic Cavity
Figure 20–2b
Relation to Thoracic Cavity
 Surrounded by pericardial sac
 Between 2 pleural cavities
 In the mediastinum
What is the structure and
function of the
pericardium?
The Pericardium
 Double lining of the pericardial cavity
Figure 20–2c
2 Layers of Pericardium
1. Parietal pericardium:
 outer layer
 forms inner layer of pericardial sac
2. Visceral pericardium:
 inner layer of pericardium
Structures of Pericardium
 Pericardial cavity:
 Is between parietal and visceral layers
 contains pericardial fluid
 Pericardial sac:
 fibrous tissue
 surrounds and stabilizes heart
Pericarditis
 An infection of the pericardium
Superficial Anatomy of the
Heart
 4 cardiac
chambers
Figure 20–3
Atria
 Thin-walled
 Expandable outer auricle
Sulci
 Coronary sulcus:
 divides atria and ventricles
 Anterior and posterior interventricular
sulci:
 separate left and right ventricles
 contain blood vessels of cardiac muscle
What are the layers
of the heart wall?
The Heart Wall
Figure 20–4
3 Layers of the Heart Wall
 Epicardium:
 outer layer
 Myocardium:
 middle layer
 Endocardium:
 inner layer
Epicardium
 Visceral pericardium
 Covers the heart
Myocardium
 Muscular wall of the heart
 Concentric layers of cardiac muscle
tissue
Cardiac Muscle Cells
Figure 20–5
Cardiac Muscle Cells
 Intercalated discs:





interconnect cardiac muscle cells
secured by desmosomes
linked by gap junctions
convey force of contraction
propagate action potentials
Characteristics of
Cardiac Muscle Cells
1. Small size
2. Single, central nucleus
3. Branching interconnections between
cells
4. Intercalated discs
Cardiac Cells vs. Skeletal Fibers
Table 20-1
What is the path of blood
flow through the heart, and
what are the major blood
vessels, chambers, and
heart valves?
Internal Anatomy
PLAY
3D Panorama of the Heart
Figure 20–6a
Atrioventricular (AV) Valves
 Connect right atrium to right ventricle
and left atrium to left ventricle
 Permit blood flow in 1 direction:
 atria to ventricles
PLAY
The Heart: Valves
Septa
 Interatrial septum:
 separates atria
 Interventricular septum:
 separates ventricles
The Vena Cava
 Delivers systemic circulation to right
atrium
 Superior vena cava:
 receives blood from head, neck, upper
limbs, and chest
 Inferior vena cava:
 receives blood from trunk, and viscera,
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 2 atria
 Seals off at birth, forming fossa ovalis
Pectinate Muscles
 Contain prominent muscular ridges
 On anterior atrial wall
 And inner surfaces of right auricle
Cusps
 Fibrous flaps that form bicuspid (2)
and tricuspid (3) valves
 Free edges attach to chordae
tendineae from papillary muscles of
ventricle
 Prevent valve from opening backward
Right Atrioventricular (AV)
Valve
 Also called tricuspid valve
 Opening from right atrium to right
ventricle
 Has 3 cusps
 Prevents backflow
PLAY
The Heart: Blood Flow
Trabeculae Carneae
 Muscular ridges on internal surface of
right ventricle
 Includes moderator band:
 ridge contains part of conducting system
 coordinates contractions of cardiac
muscle cells
The Pulmonary Circuit
 Conus arteriosus (superior right
ventricle) leads to pulmonary trunk
 Pulmonary trunk divides into left and
right pulmonary arteries
 Blood flows from right ventricle to
pulmonary trunk through pulmonary
valve
 Pulmonary valve has 3 semilunar
cusps
Return from Pulmonary Circuit
 Blood gathers into left and right
pulmonary veins
 Pulmonary veins deliver to left atrium
 Blood from left atrium passes to left
ventricle through left atrioventricular
(AV) valve
 2-cusp bicuspid valve or 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 not have moderator band
The Left Ventricle
 Systemic circulation:
 blood leaves left ventricle through aortic
valve into ascending aorta
 ascending aorta turns (aortic arch) and
becomes descending aorta
Left and Right Ventricles
 Have significant
structural differences
Figure 20–7
Structure of Left
and Right Ventricles
 Right ventricle wall is thinner,
develops less pressure than left
ventricle
 Right ventricle is pouch-shaped, left
ventricle is round
The Heart Valves
 One-way valves
prevent backflow
during contraction
Figure 20–8
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
Regurgitation
 Failure of valves
 Causes backflow of blood into atria
Semilunar Valves
 Pulmonary and aortic tricuspid valves
 Prevent backflow from pulmonary
trunk and aorta into ventricles
 Have no muscular support
 3 cusps support like tripod
Aortic Sinuses
 At base of ascending aorta
 Prevent valve cusps from sticking to
aorta
 Origin of right and left coronary
arteries
Carditis
 An inflammation of the heart
 Can result in valvular heart disease
(VHD):
 e.g., rheumatic fever
KEY CONCEPT (1 of 3)
 The heart has 4 chambers:
 2 for pulmonary circuit:
 right atrium and right ventricle
 2 for systemic circuit:
 left atrium and left ventricle
KEY CONCEPT (2 of 3)
 Left ventricle has a greater workload
 Is much more massive than right
ventricle, but the two chambers pump
equal amounts of blood
KEY CONCEPT (3 of 3)
 AV valves prevent backflow from
ventricles into atria
 Semilunar valves prevent backflow
from aortic and pulmonary trunks into
ventricles
Connective Tissue
Fibers of the Heart
1. Physically support cardiac muscle
fibers
2. Distribute forces of contraction
3. Add strength and prevent
overexpansion of heart
4. Elastic fibers return heart to original
shape after contraction
The Fibrous Skeleton
 4 bands around heart valves and
bases of pulmonary trunk and aorta
 Stabilize valves
 Electrically insulate ventricular cells
from atrial cells
How is the heart
supplied with blood?
Blood Supply to the Heart
 Coronary circulation
Figure 20–9
Coronary Circulation
 Coronary arteries and cardiac veins
 Supplies blood to muscle tissue of
heart
Coronary Arteries
 Left and right
 Originate at aortic sinuses
 High blood pressure, elastic rebound
force blood through coronary arteries
between contractions
Right Coronary Artery
 Supplies blood to:
 right atrium
 portions of both ventricles
 cells of sinoatrial (SA) and
atrioventricular nodes
 marginal arteries (surface of right
ventricle)
 posterior interventricular artery
Left Coronary Artery
 Supplies blood to:
 left ventricle
 left atrium
 interventricular septum
Cardiac Veins (1 of 3)
 Great cardiac vein:
 drains blood from area of anterior
interventricular artery into coronary
sinus
Cardiac Veins (2 of 3)
 Anterior cardiac vein:
 empties into right atrium
Cardiac Veins (3 of 3)
 Posterior cardiac vein, middle cardiac
vein, and small cardiac vein:
 empty into great cardiac vein or
coronary sinus
The Cardiac Cycle
Figure 20–11
The Heartbeat
 A single contraction of the heart
 The entire heart contracts in series:
 first the atria
 then the ventricles
2 Types of Cardiac Muscle Cells
 Conducting system:
 controls and coordinates heartbeat
 Contractile cells:
 produce contractions
The Cardiac Cycle
 Begins with action potential at SA
node
 transmitted through conducting system
 produces action potentials in cardiac
muscle cells (contractile cells)
PLAY
InterActive Physiology: Cardiovascular
System: Cardiac Action Potential
Electrocardiogram (ECG)
 Electrical events in the cardiac cycle
can be recorded on an
electrocardiogram (ECG)
What is the difference
between nodal cells and
conducting cells; what are
the components and
functions of the conducting
system of the heart?
The Conducting System
Figure 20–12
The Conducting System
 A system of specialized cardiac
muscle cells:
 initiates and distributes electrical
impulses that stimulate contraction
 Automaticity:
 cardiac muscle tissue contracts
automatically
Structures of the
Conducting System
 Sinoatrial (SA) node
 Atrioventricular (AV) node
 Conducting cells
Conducting Cells
 Interconnect SA and AV nodes
 Distribute stimulus through
myocardium
 In the atrium:
 internodal pathways
 In the ventricles:
 AV bundle and bundle branches
Prepotential
 Also called pacemaker potential
 Resting potential of conducting cells:
 gradually depolarizes toward threshold
 SA node depolarizes first, establishing
heart rate
Heart Rate
 SA node generates 80–100 action
potentials per minute
 Parasympathetic stimulation slows
heart rate
 AV node generates 40–60 action
potentials per minute
Impulse Conduction
through the Heart
Figure 20–13
The Sinoatrial (SA) Node
 In posterior wall of right atrium
 Contains pacemaker cells
 Connected to AV node by internodal
pathways
 Begins atrial activation (Step 1)
The Atrioventricular (AV) Node
 In floor of right atrium
 Receives impulse from SA node (Step
2)
 Delays impulse (Step 3)
 Atrial contraction begins
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
4. The Purkinje Fibers
 Distribute impulse through ventricles
(Step 5)
 Atrial contraction is completed
 Ventricular contraction begins
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
What electrical events
are associated with a
normal electrocardiogram?
The Electrocardiogram
Figure 20–14b
Electrocardiogram (ECG or
EKG)
 A recording of electrical events in the
heart
 Obtained by electrodes at specific
body locations
 Abnormal patterns diagnose damage
Features of an ECG
 P wave:
 atria depolarize
 QRS complex:
 ventricles depolarize
 T wave:
 ventricles repolarize
Cardiac Arrhythmias
 Abnormal patterns of cardiac
electrical activity
KEY CONCEPT (1 of 3)
 Heart rate is normally established by
cells of SA node
 Rate can be modified by autonomic
activity, hormones, and other factors
KEY CONCEPT (2 of 3)
 From the SA node, stimulus is
conducted to AV node, AV bundle,
bundle branches, and Purkinje fibers
before reaching ventricular muscle
cells
KEY CONCEPT (3 of 3)
 Electrical events associated with the
heartbeat can be monitored in an
electrocardiogram (ECG)
Contractile Cells
 Purkinje fibers distribute the stimulus
to the contractile cells, which make
up most of the muscle cells in the
heart
What events take
place during an action
potential in cardiac
muscle?
Action Potentials in
Skeletal and Cardiac Muscle
Figure 20–15
Resting Potential
 Of a ventricular cell:
 about —90 mV
 Of an atrial cell:
 about —80 mV
3 Steps of
Cardiac Action Potential
1. Rapid depolarization:
 voltage-regulated sodium channels (fast
channels) open
3 Steps of
Cardiac Action Potential
2. As sodium channels close:
 voltage-regulated calcium channels
(slow channels) open
 balance Na+ ions pumped out
 hold membrane at 0 mV plateau
3 Steps of
Cardiac Action Potential
3. Repolarization:




plateau continues
slow calcium channels close
slow potassium channels open
rapid repolarization restores resting
potential
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
and tetany
What is the importance
of calcium ions to
the contractile process?
Calcium and Contraction
 Contraction of a cardiac muscle cell is
produced by an increase in calcium
ion concentration around myofibrils
2 Steps of Calcium
Ion Concentration
1. 20% of calcium ions required for a
contraction:
 calcium ions enter cell membrane during
plateau phase
2 Steps of Calcium
Ion Concentration
2. Arrival of extracellular Ca2+:
 triggers release of calcium ion reserves
from sarcoplasmic reticulum
Intracellular and
Extracellular Calcium
 As slow calcium channels close:
 intracellular Ca2+ is absorbed by the SR
 or pumped out of cell
 Cardiac muscle tissue:
 very sensitive to extracellular Ca2+
concentrations
What events take place
during the cardiac cycle,
including atrial and
ventricular systole and
diastole?
The Cardiac Cycle
 The period between the start of 1
heartbeat and the beginning of the
next
 Includes both contraction and
relaxation
PLAY
InterActive Physiology: Cardiovascular
System: The Cardiac Cycle
2 Phases of the Cardiac Cycle
 Within any 1 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
Phases of the Cardiac Cycle
Figure 20–16
4 Phases of the Cardiac Cycle
1.
2.
3.
4.
Atrial systole
Atrial diastole
Ventricular systole
Ventricular diastole
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
Pressure and Volume
in the Cardiac Cycle
 8 steps in the cardiac cycle
Figure 20–17
8 Steps in the Cardiac Cycle
1. Atrial systole:
 atrial contraction begins
 right and left AV valves are open
8 Steps in the Cardiac Cycle
2. Atria eject blood into ventricles:
 filling ventricles
8 Steps in the Cardiac Cycle
3. Atrial systole ends:
 AV valves close
 ventricles contain maximum volume
 end-diastolic volume (EDV)
8 Steps in the Cardiac Cycle
4. Ventricular systole:
 isovolemic ventricular contraction
 pressure in ventricles rises
 AV valves shut
8 Steps in the Cardiac Cycle
5. Ventricular ejection:
 semilunar valves open
 blood flows into pulmonary and aortic
trunks
 Stroke volume (SV) = 60% of enddiastolic volume
8 Steps in the Cardiac Cycle
6. Ventricular pressure falls:
 semilunar valves close
 ventricles contain end-systolic volume
(ESV), about 40% of end-diastolic
volume
8 Steps in the Cardiac Cycle
7. Ventricular diastole:
 ventricular pressure is higher than atrial
pressure
 all heart valves are closed
 ventricles relax (isovolumetric
relaxation)
8 Steps in the Cardiac Cycle
8. Atrial pressure is higher than
ventricular pressure:




AV valves open
passive atrial filling
passive ventricular filling
cardiac cycle ends
PLAY
The Heart: Cardiac Cycle
Heart Failure
 Lack of adequate blood flow to
peripheral tissues and organs due to
ventricular damage
How do heart sounds
relate to specific events
in the cardiac cycle?
Heart Sounds
Figure 20–18b
4 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
Positioning the Stethoscope
 To detect sounds
of each valve
Figure 20–18a
Heart Murmur
 Sounds produced by regurgitation
through valves
What is cardiac output,
and what factors influence
it?
Cardiodynamics
 The movement and force generated
by cardiac contractions
PLAY
InterActive Physiology: Cardiovascular
System: Cardiac Output
Important Cardiodynamics
Terms
 End-diastolic volume (EDV)
 End-systolic volume (ESV)
 Stroke volume (SV):
SV = EDV — ESV
Important Cardiodynamics
Terms
 Ejection fraction:
 the percentage of EDV represented by
SV
 Cardiac output (CO):
 the volume pumped by each ventricle in
1 minute
Stroke Volume
 Volume (ml) of blood ejected per beat
Figure 20–19
Cardiac Output
 Cardiac output (CO) ml/min =
 Heart rate (HR) beats/min 
 Stroke volume (SV) ml/beat
Adjusting to Conditions
 Cardiac output:
 adjusted by changes in heart rate or
stroke volume
 Heart rate:
 adjusted by autonomic nervous system
or hormones
 Stroke volume:
 adjusted by changing EDV or ESV
What variables
influence heart rate?
Autonomic Innervation
Figure 20–21 (Navigator)
Autonomic Innervation (1 of 4)
 Cardiac plexuses:
 innervate heart
 Vagus nerves (X):
 carry parasympathetic preganglionic
fibers to small ganglia in cardiac plexus
Autonomic Innervation (2 of 4)
 Cardiac centers of medulla oblongata:
 cardioacceleratory center:
 controls sympathetic neurons (increase
heart rate)
 cardioinhibitory center:
 controls parasympathetic neurons (slow
heart rate)
Autonomic Innervation (3 of 4)
 Cardiac reflexes:
 Cardiac centers monitor:
 baroreceptors (blood pressure)
 chemoreceptors (arterial oxygen and
carbon dioxide levels)
 Cardiac centers adjust cardiac activity
Autonomic Innervation (4 of 4)
 Autonomic tone:
 dual innervation maintains resting tone
by releasing Ach and NE
 fine adjustments meet needs of other
systems
Autonomic Pacemaker
Regulation
Figure 20–22
Autonomic Pacemaker
Regulation (1 of 3)
 Sympathetic and parasympathetic
stimulation:
 greatest at SA node (heart rate)
 Membrane potential of pacemaker
cells:
 lower than other cardiac cells
Autonomic Pacemaker
Regulation (2 of 3)
 Rate of spontaneous depolarization
depends on:
 resting membrane potential
 rate of depolarization
Autonomic Pacemaker
Regulation (3 of 3)
 ACh (parasympathetic stimulation):
 slows the heart
 NE (sympathetic stimulation):
 speeds the heart
Atrial Reflex
 Also called Bainbridge reflex
 Adjusts heart rate in response to
venous return
 Stretch receptors in right atrium:
 trigger increase in heart rate
 through increased sympathetic activity
Hormonal Effects on Heart Rate
 Increase heart rate (by sympathetic
stimulation of SA node):
 epinephrine (E)
 norepinephrine (NE)
 thyroid hormone
What variables influence
stroke volume?
Hormones and Contractility
 Many hormones affect heart
contraction
 Pharmaceutical drugs mimic hormone
actions:
 stimulate or block beta receptors
 affect calcium ions e.g., calcium channel
blockers
How are adjustments in
stroke volume and cardiac
output coordinated at
different levels of activity?
Factors Affecting Heart
Rate and Stroke Volume
Figure 20–24
Heart Rate Control Factors
1. Autonomic nervous system:
 sympathetic and parasympathetic
2. Circulating hormones
3. Venous return and stretch receptors
KEY CONCEPT (1 of 2)
 Cardiac output:
 the amount of blood pumped by the left
ventricle each minute
 adjusted by the ANS in response to:
 circulating hormones
 changes in blood volume
 alterations in venous return
KEY CONCEPT (2 of 2)
 Most healthy people can increase
cardiac output by 300–500%
The Heart and
Cardiovascular System
 Cardiovascular regulation:
 ensures adequate circulation to body
tissues
 Cardiovascular centers:
 control heart and peripheral blood
vessels
The Heart and
Cardiovascular System
 Cardiovascular system responds to:
 changing activity patterns
 circulatory emergencies
SUMMARY (1 of 7)
 Organization of cardiovascular
system:
 pulmonary and systemic circuits
 3 types of blood vessels:
 arteries, veins, and capillaries
SUMMARY (2 of 7)
 4 chambers of the heart:
 left and right atria
 left and right ventricles
SUMMARY (3 of 7)
 Pericardium, mediastinum, and
pericardial sac
 Coronary sulcus and superficial
anatomy of the heart
 Structures and cells of the heart wall
SUMMARY (4 of 7)
 Internal anatomy and structures of
the heart:
 septa, muscles, and blood vessels
 Valves of the heart and direction of
blood flow
 Connective tissues of the heart
SUMMARY (5 of 7)
 Coronary blood supply
 Contractile cells and the conducting
system:
 pacemaker calls, nodes, bundles, and
Purkinje fibers
SUMMARY (6 of 7)
 Electrocardiogram and its wave forms
 Refractory period of cardiac cells
 Cardiac cycle:
 atrial and ventricular
 systole and diastole
SUMMARY (7 of 7)
 Cardiodynamics:
 stroke volume and cardiac output
 Control of cardiac output