Download cardiac muscle cells

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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Introduction to Cardiovascular System
 Three Types of Blood Vessels
 Arteries
 Carry blood away from heart
 Veins
 Carry blood to heart
 Capillaries
 Networks between arteries and veins
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Introduction to Cardiovascular System
 Capillaries
 Also called exchange vessels
 Exchange materials between blood and
tissues
 Materials include dissolved gases, nutrients,
wastes
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Introduction to Cardiovascular System
Figure 20–1 An Overview of the Cardiovascular System.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Introduction to Cardiovascular System
 Four Chambers of the Heart
 Right atrium
 Collects blood from systemic circuit
 Right ventricle
 Pumps blood to pulmonary circuit
 Left atrium
 Collects blood from pulmonary circuit
 Left ventricle
 Pumps blood to systemic circuit
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
 The Pericardium
 Double lining of the pericardial cavity
 Parietal pericardium
 Outer layer
 Forms inner layer of pericardial sac
 Visceral pericardium
 Inner layer of pericardium
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Figure 20–2c
Anatomy of the Heart
 The Pericardium
 Pericardial cavity
 Is between parietal and visceral layers
 Contains pericardial fluid
 Pericardial sac
 Fibrous tissue
 Surrounds and stabilizes heart
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Pericarditis
 An infection of the pericardium
 An inflammation of the sac that envelops the
heart (pericarditis) causes pain that worsens
when the person lies down and decreases
when the person sits up and leans forward.
Exertion does not increase the pain, but
inhaling deeply does. Pain increased by
inhaling deeply can also be caused by an
inflammation of the membranes covering the
lungs (pleurisy).
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
Figure 20–2b The Location of the Heart in the Thoracic Cavity
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
Figure 20–c2 The Location of the Heart in the Thoracic Cavity
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
Figure 20–3c The Superficial Anatomy of the Heart
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
 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 wraps around great vessels
 Two divisions of ventricular myocardium
 Endocardium (inner layer)
 Simple squamous epithelium
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
Figure 20–4 The Heart Wall
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Carditis
 An inflammation of the heart
 Can result in valvular heart disease (VHD):
(heart disease caused by stenosis of the
cardiac valves and obstructed blood flow
or caused by degeneration and blood
regurgitation)
 e.g., rheumatic fever
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
 Cardiac Muscle Tissue
 Intercalated discs
 Interconnect cardiac muscle cells
 Secured by desmosomes
 Linked by gap junctions
 Convey force of contraction
 Propagate action potentials
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
Figure 20–5 Cardiac Muscle Cells
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
Figure 20–5 Cardiac Muscle Cells
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
 The Cardiac (Fibrous) Skeleton
 Four bands around heart valves and bases of
pulmonary trunk and aorta
 Stabilize valves
 Electrically insulate ventricular cells from atrial
cells
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
 The Blood Supply to the Heart = Coronary
Circulation
 Coronary arteries and cardiac veins
 Supplies blood to muscle tissue of heart
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
 The Coronary Arteries
 Left and right
 Originate at aortic sinuses
 High blood pressure, elastic rebound forces
blood through coronary arteries between
contractions
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
 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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Anatomy of the Heart
 Left Coronary Artery
 Supplies blood to
 Left ventricle
 Left atrium
 Interventricular septum
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
 Heartbeat
 A single contraction of the heart
 The entire heart contracts in series
 First the atria
 Then the ventricles
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
 Two Types of Cardiac Muscle Cells
 Conducting system
 Controls and coordinates heartbeat
 Contractile cells
 Produce contractions that propel blood
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
 The Cardiac Cycle
 Begins with action potential at SA node
 Transmitted through conducting system
 Produces action potentials in cardiac muscle cells (contractile
cells)
 Electrocardiogram (ECG)
 Electrical events in the cardiac cycle can be recorded on an
electrocardiogram (ECG)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
Figure 20–11 An Overview of Cardiac Physiology
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
 A system of specialized cardiac muscle
cells
 Initiates and distributes electrical impulses
that stimulate contraction
 Automaticity
 Cardiac muscle tissue contracts automatically
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
 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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
 Prepotential
 Also called pacemaker potential
 Resting potential of conducting cells
 Gradually depolarizes toward threshold
 SA node depolarizes first, establishing heart
rate
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
Figure 20–12 The Conducting System of the Heart
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
 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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
Figure 20–13 Impulse Conduction through the Heart
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
Figure 20–13 Impulse Conduction through the Heart
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
Figure 20–13 Impulse Conduction through the Heart
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
Figure 20–13 Impulse Conduction through the Heart
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
Figure 20–13 Impulse Conduction through the Heart
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
 Electrocardiogram (ECG or EKG)
 A recording of electrical events in the heart
 Obtained by electrodes at specific body
locations
 Abnormal patterns diagnose damage
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
 Features of an ECG
 P wave
 Atria depolarize
 QRS complex
 Ventricles depolarize
 T wave
 Ventricles repolarize
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
 Time Intervals Between ECG Waves
 P–R interval
 From start of atrial depolarization
 To start of QRS complex
 Q–T interval
 From ventricular depolarization
 To ventricular repolarization
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
Figure 20–14a An Electrocardiogram: Electrode Placement for
Recording a Standard ECG
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
Figure 20–14b An Electrocardiogram: An ECG Printout
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
 Contractile Cells
 Purkinje fibers distribute the stimulus to the
contractile cells, which make up most of the
muscle cells in the heart
 Resting Potential
 Of a ventricular cell: about –90 mV
 Of an atrial cell: about –80 mV
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
Figure 20–15 The Action Potential in Skeletal and Cardiac Muscle
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
 The Role of Calcium Ions in Cardiac
Contractions
 Contraction of a cardiac muscle cell is
produced by an increase in calcium ion
concentration around myofibrils
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
 The Role of Calcium Ions in Cardiac
Contractions
 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 from sarcoplasmic
reticulum
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Conducting System
 The Role of Calcium Ions in Cardiac
Contractions
 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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Cardiac Cycle
 Cardiac cycle = The period between the
start of one heartbeat and the beginning of
the next
 Includes both contraction and relaxation
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Cardiac Cycle
 Phases of the Cardiac Cycle
 Within any one chamber
 Systole (contraction)
 Diastole (relaxation)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Cardiac Cycle
Figure 20–16 Phases of the Cardiac Cycle
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Cardiac Cycle
 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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Cardiac Cycle
Eight Steps in the Cardiac Cycle
1. 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)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Cardiac Cycle
Figure
20–17
Pressure
andasVolume
Relationships
in the Cardiac Cycle
Copyright © 2009
Pearson Education,
Inc., publishing
Pearson Benjamin
Cummings
The Cardiac Cycle
Eight Steps in the Cardiac Cycle
4. Ventricular systole

Isovolumetric ventricular contraction

Pressure in ventricles rises

AV valves shut
5. Ventricular ejection

Semilunar valves open

Blood flows into pulmonary and aortic trunks

Stroke volume (SV) = 60% of end-diastolic volume
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Cardiac Cycle
Eight Steps in the Cardiac Cycle
6. Ventricular pressure falls

Semilunar valves close

Ventricles contain end-systolic volume (ESV), about 40%
of end-diastolic volume
7. Ventricular diastole

Ventricular pressure is higher than atrial pressure

All heart valves are closed

Ventricles relax (isovolumetric relaxation)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Cardiac Cycle
Eight 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
The Heart: Cardiac Cycle
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Cardiac Cycle
 Heart Murmur
 Sounds produced by regurgitation through
valves
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Regurgitation
 Failure of valves
 Causes backflow of blood into atria
 Tricuspid regurgitation (tricuspid
incompetence, tricuspid insufficiency) is
leakage of blood backward through the
tricuspid valve each time the right ventricle
contracts.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
 Tricuspid regurgitation usually results when the
right ventricle enlarges and resistance to blood
flow from the right ventricle to the lungs is
increased. Resistance may be increased by a
severe, long-standing lung disorder, such as
emphysema or pulmonary hypertension, or by
narrowing of the pulmonary valve (pulmonary
stenosis). To compensate, the right ventricle
enlarges and thickens so that it can pump
harder, and the valve opening stretches.
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Cardiac Cycle
Figure 20–18 Heart Sounds
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiodynamics
Figure 20–19 A Simple Model of Stroke Volume
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiodynamics
 Cardiac Output
 CO = HR X SV
 CO = cardiac output (mL/min)
 HR = heart rate (beats/min)
 SV = stroke volume (mL/beat)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiodynamics
 Factors Affecting Cardiac Output
 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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiodynamics
Figure 20–20 Factors Affecting Cardiac Output
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiodynamics
Figure 20–24 A Summary of the Factors Affecting Cardiac Output
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiodynamics
 Factors Affecting the Heart Rate
 Autonomic innervation
 Cardiac plexuses: innervate heart
 Vagus nerves (X): carry parasympathetic preganglionic fibers
to small ganglia in cardiac plexus
 Cardiac centers of medulla oblongata:
– cardioacceleratory center controls sympathetic
neurons (increases heart rate)
– cardioinhibitory center controls parasympathetic
neurons (slows heart rate)
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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 by
releasing ACh and NE
 Fine adjustments meet needs of other systems
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiodynamics
Figure 20–21 Autonomic Innervation of the Heart
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiodynamics
 Effects on the SA Node
 Sympathetic and parasympathetic stimulation
 Greatest at SA node (heart rate)
 Membrane potential of pacemaker cells
 Lower than other cardiac cells
 Rate of spontaneous depolarization depends on
 Resting membrane potential
 Rate of depolarization
 ACh (parasympathetic stimulation)
 Slows the heart
 NE (sympathetic stimulation)
 Speeds the heart
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiodynamics
 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
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiodynamics
 Hormonal Effects on Heart Rate
 Increase heart rate (by sympathetic
stimulation of SA node)
 Epinephrine (E)
 Norepinephrine (NE)
 Thyroid hormone
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiodynamics
Figure 20–23 Factors Affecting Stroke Volume
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Cardiodynamics
 The Heart and Cardiovascular System
 Cardiovascular regulation
 Ensures adequate circulation to body tissues
 Cardiovascular centers
 Control heart and peripheral blood vessels
 Cardiovascular system responds to
 Changing activity patterns
 Circulatory emergencies
Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings