Cardiovascular System
Function: to pump blood to all parts of the body
Location of the Heart in the Thoracic Cavity
-> Mediastinum (“midway”) – central compartment of the thoracic
cavity
2. Aortic Valve – controls the blood flow from the left
ventricle to the aorta
3. Atrio-Ventricular Valve
 Tricuspid Valve – right Atrio-Ventricular Valve
 Bicuspid Valve or Mitral Valve – left AtrioVentricular Valve
1. Heart – anatomical pump; pressure gradient;
2. Blood vessels - passageways
 Arteries – largest
 Veins
 Capillaries – smallest
3. Blood – transport medium (oxygen, carbon dioxide, nutrients,
wastes, electrolytes, and hormones)
Circulations – forms a figure 8
Pulmonary circulation – heart and lungs
Systemic circulation – heart and organ systems
Anatomy of the heart
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Atria
 Upper chambers
 RECEIVES blood
Ventricle
 Lower chamber
 More muscle fibers; pumps blood from the heart
Pulmonary arteries – carry blood away from the ventricles
Pulmonary veins – return blood from tissues to the atria
Valves – controls the blood flow from atrium to ventricle and
prevents backflow
1. Pulmonary Valve – controls the blood flow from the
right ventricle to the pulmonary arteries
Organization of Cardiac Muscles
Cardiac walls – composed of spirally arranged cardiac muscle
fibers:
1. Endocardium (thin inner) – unique type of epithelial tissue
that lines the chambers of the heart
2. Myocardium (thick middle layer) – cardiac muscles that
consists of interlacing bundles -> intercalated disc)
3. Epicardium (thin external layer) – covers the heart
4. Pericardium (outermost later)
 Protects the heart against infection
 Provides lubrication
 Fixes the heart to mediastinum
2 layers of pericardium
 Serous layer
 Fibrous layer
2 Types of membrane junctions are present within intercalated disc
Intercalated disc – composed of cell adhesion molecules that
connects cardiac muscle to another by fusion:
1. Gap junctions - connect and facilitate communication
between the two muscle cells (electrical signals)
2. Desmosomes – to hold together the two muscles
Pericarditis - pericardial sac inflammation
 Effect: painful friction between two pericardial layers
 Cause: viral or bacterial infection
Electrical Activity of the Heart
Autorhythmicity (or automaticity) - the heart rhythmically
contracts because of action potentials that it generates by itself
2 specialized types of cardiac muscle cells
Electrical activity -> Mechanical activity
1. Contractile cells (99%) “working cells”
 Do mechanical work of pumping
 these cells normally do not initiate their action
potentials
 atria, ventricles, valves
2. Autorhythmic cells
 Non-contractile cardiac cells specialized for initiating
and conducting the action potentials responsible for
contraction of the working cells
 Receive electrical signal that initiates action potential
for contraction
a. Sinoatrial node (SA node)
 PACEMAKER of the heart
 Start of the initial electrical activity
 Interatrial pathway (Bachmann’s) - spreads
throughout both atria
 a group of autorhythmic cells that are located
between vena cava and the right atrium
b. Atrioventricular node (AV)
 Located at the base of the right atrium near
the septum above between the atria and
ventricles
 Internodal pathways - action potential spread
from the atria to the ventricles
c. Bundle of His (atrioventricular bundle)
 Divides to form the bundle branches that
curves around the ventricular chambers
d. Purkinje fibers (looks like small twigs of a tree
branch)
 Small terminal fibers that extend from the
bundle of His
 Spread throughout the ventricular myocardium
Pacemaker Potential in Autorhythmic Cells
Pacemaker activity - cardiac autorhythmic cells do not have a
resting potential
D: Lowest Point
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K+ : close channels
Na+ : open channels
Action Potential in Cardiac Contractile Cells
Occurs at the ventricular to contract cardiac muscles
E: Pacemaker potential (slow depolarization)
 K+ : closed channels
 Na+ : opened channels, leak or funny channels (influx)
 T-type Ca2+ [Tiny channels] : open channels (influx)
A: Threshold (fast depolarization)
 L-type Ca2+ channels [Large channels] open channels
(influx)
 Na+ : close channels
B: Peak of the Pacemaker potential
 Ca2+: close channels
 K+: open channels
C: Repolarization
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K+ : goes outside the cell
4: Resting potential
 K+ : open channels (goes outside the cells)
0: Depolarization
 Na+ : open channels (influx)
1: Repolarization
 Na+ : close channels (influx)
 K+ : open channels (fast efflux)
2: Slow entry of Ca2+
 K+ : open channels (slow efflux)
 L-type Ca2+ : open channels (influx)
3: Repolarization
 K+ : open channels (goes outside the cells)
 L-type Ca2+ : close channels (influx)
Autorhythmic and Contractile Cells
Actin and Myosin – responsible for contraction
Electrocardiogram (ECG)
 Biomedical device that records the electrical activity present in
body fluids from the cardiac impulse that reaches the body
surface,
 Indirect recording of the actual electrical activity of the heart.
 Representing the overall spread of activity throughout the
heart during depolarization and repolarization
P wave rate 60-100 bpm with 10% variation – Normal = 75
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Sinus Bradicardycardia: Rate < 60 bpm slow heartbeat
Sinus Tachychardia: Rate > 100 bpm fast heartbeat
Results from:
- Pain/Anxiety
- Volume depletion
- Pericarditis
- Chronotropic drugs (dopamine)
Abnormalities in Heart Rhythm
Arrhythmia – Any variation from the normal rhythm and sequence
of excitation of the heart
ECG Waves
3 distinct wave-forms:
1. P wave – ATRIAL depolarization
 Filling of blood in the atria
 PR segment (AV nodal delay) – opening the valve
2. QRS wave – VENTRICULAR depolarization
 Blood is pumped out of the atrium
 ST SEGMENT– contraction of ventricles;
emptying
3. T wave – VENTRICULAR repolarization
 K+ goes out repolarizing the cell
 TP segment – relaxing and filling
Hearth Rhythm and Heart Rate
Normal sinus rhythm – heart rhythm
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Formula: 1500/(small x big boxes)
Other method: 60/0.2 x big box
Atrial fibrillation has irregular distance while atrial flutter has
equal distance
Thromboembolism – blood clot; clogging of vessels
Cardio version – small plates with lower voltage input compared
to defibrillator
Mechanical Events of the Cardiac Cycle
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Heart Murmurs
Contraction
Relaxation
Resultant changes in blood flow through the heart
Cardiac cycle alternate periods
Systole – contraction and emptying
Diastole – relaxation and filling
Stages of Cardiac Cycle
1. Filling phase – ventricles fill during diastole and atrial
systole
2. Isovolumetric contraction – ventricles contract, building up
pressure ready to pump blood into the aorta/pulmonary
trunk
3. Outflow phase (ventricular systole) – the ventricles
continue to contract, pushing blood into the aorta and the
pulmonary trunk
4. Isovolumetric relaxation (ventricular diastole) – the
ventricles relax, ready to re-fill with blood in the next filling
phase
Laminar (layer) flow
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normal flow of the blood in which layers of the fluid slide
smoothly over one another
does not produce an audible sound
Turbulent flow
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a turbulent sound/murmurs can be heart from the heart
Cardiac Output (CO)
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the volume of blood pumped by each ventricle per minute
depends on heart rate (HR) and stroke volume (SV)
Cardiac Output = Average HR x Average SV
Determined by stroke volume
Cardiac Reserve
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Difference between the cardiac output at rest and the
max volume of blood the heart can pump per minute
Stroke Volume = EDV - ESV
Influence:
1. Intrinsic control related to the extent of venous return
2. Extrinsic control related to the extent of sympathetic
stimulation of the heart
Ejection Fraction = SV/EDV
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Healthy heart – EF= 50% - 70%
Heart during strenuous exercise – EF = 90%
Failing heart – EF= 30% or less
Heart failure (HF) – the inability of CO to keep pace with the
body’s demands for supplies and removal of wastes
Heart Diseases associated with Coronary circulation (Coronary
Artery Disease)
1. Vascular Spasm
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Abnormal spastic constriction that transiently narrows
the coronary vessels
Vasoconstriction of blood vessel because of damaged
blood vessel to prevent the leakage of blood
2. Atherosclerosis
3. Thromboembolism
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formation in a blood vessel of a clot (thrombus) that
breaks loose and is carried by the blood stream to
plug another vessel
embolus – piece of clot
thrombus – blood clot