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THE CARDIOVASCULAR
SYSTEM: HEART
Lab and Lecture Notes
LAB MATERIAL
Location
 Thoracic cavity between two lungs
 ~2/3 to left of midline
 surrounded by pericardium:
 Fibrous pericardium Inelastic and anchors heart in place
 Inside is serous pericardium- double layer
around heart
 Parietal layer fused to fibrous pericardium
 Inner visceral layer adheres tightly to heart
 Filled with pericardial fluid- reduces friction during
beat.
Figure 15.1
Heart Wall
 Epicardium- outer layer
 Myocardium- cardiac muscle
 Two separate networks via gap junctions in
intercalated discs- atrial & ventricular
 Networks- contract as a unit
 Endocardium- Squamous epithelium
 lines inside of myocardium
Figure 15.2a
Figure 15.2b
Figure 15.2c
Chambers
 4 chambers
 2 upper chambers= Atria
 Between is interatrial septum
 Contains fossa ovalis- remnant of foramen ovalis
 2 lower chambers = ventricles
 Between is interventricular septum
 Wall thickness depends on work load
 Atria thinnest
 Right ventricle pumps to lungs & thinner than left
Great Vessels Of Heart- Right
 Superior & inferior Vena Cavae
 Delivers deoxygenated blood to R. atrium
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from body
 Coronary sinus drains heart muscle veins
R. Atrium Tricuspid Valve R. Ventricle
pumps through Pulmonary Trunk
R & L pulmonary arteries
 lungs
Great Vessels Of Heart-Left
 Pulmonary Veins from lungs
 oxygenated blood
 L. atriumBicusid (Mitral) Valve Left
ventricle
 ascending aorta body
 Between pulmonary trunk & aortic arch is
ligamentum arteriosum
 fetal ductus arteriosum remnant
Figure 15.3a
Figure 15.3b
Figure 15.3c
Valves
 Designed to prevent back flow in response
to pressure changes
 Atrioventricular (AV) valves
 Between atria and ventricles
 Right = tricuspid valve (3 cusps)
 Left = bicuspid or mitral valve
 Semilunar valves near origin of aorta &
pulmonary trunk
 Aortic & pulmonary valves respectively
Figure 15.4ab
Figure 15.4c
Figure 15.4d
Figure 15.5a
Figure 15.5b
Blood Supply Of Heart
 Blood flow through vessels in myocardium =
coronary circulation
 L. & Right coronary arteries
 branch from aorta
 branch to carry blood throughout muscle
 Deoxygenated blood collected by Coronary
Sinus (posterior)
 Empties into R. Atrium
LECTURE MATERIAL
Conduction System
 1% of cardiac muscle generate action
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potentials= Pacemaker & Conduction system
Normally begins at sinoatrial (SA) node
Atria & atria contract
AV node -slows
AV bundle (Bundle of His)
bundle branches Purkinje fibers
 apex and up- then ventricles contract
Pacemaker
 Depolarize spontaneously
 sinoatrial node ~100times /min
 also AV node ~40-60 times/min
 in ventricle ~20-35 /min
 Fastest one run runs the heart = pacemaker
 Normally the sinoatrial node
Figure 15.6
Electrocardiogram
 Recording of currents from cardiac
conduction on skin = electrocardiogram
(EKG or ECG)
 P wave= atrial depolarization
 Contraction begins right after peak
 Repolarization is masked in QRS
 QRS complex= Ventricular depolarization
 Contraction of ventricle
 T-wave = ventricular repolarization
 Just after ventricles relax
Figure 15.7
Cardiac Cycle
 after T-wave ventricular diastole
 Ventricular pressure drops below atrial & AV valves
open  ventricular filling occurs
 After P-wave atrial systole
 Finishes filling ventricle (`25%)
 After QRS ventricular systole
 Pressure pushes AV valves closed
 Pushes semilunar valves open and ejection occurs
 Ejection until ventricle relaxes enough for arterial
pressure to close semilunar valves
Action Potential
 Review muscle
 Heart has addition of External Ca2+
 creates a plateau
 prolonged depolarized period.
 Can not go into tetanus.
Figure 15.8
Flow Terms
 Cardiac Output (CO) = liters/min pumped
 Heart Rate (HR) = beats/minute (bpm)
 Stroke volume (SV) = volume/beat

CO = HR x SV
Controls- Stroke Volume
(S.V.)
 Degree of stretch = Frank-Starling law
 Increase diastolic Volume increases strength of
contraction increased S.V.
 Increased venous return  increased S.V.
 increased sympathetic activity
 High back pressure in artery  decreased S.V.
 Slows semilunar valve opening
Controls- Heart Rate
 Pacemaker adjusted by nerves
 Cardiovascular center in Medulla
 parasympathetic- ACh slows
 Via vagus nerve
 Sympathetic - norepinephrine speeds
 Sensory input for control:
 baroreceptors (aortic arch & carotid sinus)- B.P.
 Chemoreceptors- O2, CO2, pH
Other Controls
 Hormones:
 Epinephrine & norepinephrine increase H.R.
 Thyroid hormones stimulate H.R.
 Called tachycardia
 Ions
 Increased Na+ or K+ decrease H.R. &
contraction force
 Increased Ca2+ increases H.R. & contraction
force
Figure 15.9
Exercise
 Aerobic exercise (longer than 20 min)
strengthens cardiovascular system
 Well trained athlete doubles maximum
C.O.
 Resting C.O. about the same but resting H.R.
decreased
Figure 15.10