Upload
gillian-perkins
View
217
Download
1
Tags:
Embed Size (px)
Citation preview
THE CARDIOVASCULAR SYSTEM: HEART
CHAPTER 15
LOCATION
Thoracic cavity between two lungs~2/3 to left of midlinesurrounded by pericardium:Fibrous pericardium- Inelastic and anchors heart in placeInside is serous pericardium-
double layer around heartParietal layer fused to fibrous pericardiumInner visceral layer adheres tightly to heartFilled with pericardial fluid- reduces friction during beat.
FIGURE 15.1
HEART WALL
Epicardium- outer layerMyocardium- cardiac muscle Two separate networks via gap junctions in intercalated discs- atrial & ventricular
Networks- contract as a unitEndocardium- Squamous epitheliumlines inside of myocardium
FIGURE 15.2A
FIGURE 15.2B
FIGURE 15.2C
CHAMBERS
4 chambers2 upper chambers= AtriaBetween is interatrial septumContains fossa ovalis- remnant of foramen ovalis
2 lower chambers = ventriclesBetween is interventricular septum
Wall thickness depends on work load
Atria thinnestRight ventricle pumps to lungs & thinner than left
GREAT VESSELS OF HEART- RIGHT
Superior & inferior Vena CavaeDelivers deoxygenated blood to R. atrium from body
Coronary sinus drains heart muscle veinsR. Atrium R. Ventriclepumps through Pulmonary TrunkR & L pulmonary arteries lungs
GREAT VESSELS OF HEART-LEFT
Pulmonary Veins from lungsoxygenated bloodL. atrium Left ventricleascending aorta bodyBetween pulmonary trunk & aortic
arch is ligamentum arteriosumfetal 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) valvesBetween atria and ventriclesRight = tricuspid valve (3 cusps)Left = bicuspid or mitral valveSemilunar 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 HEARTBlood flow through vessels in
myocardium = coronary circulationL. & Right coronary arteries branch from aortabranch to carry blood throughout muscleDeoxygenated blood collected by
Coronary Sinus (posterior)Empties into R. Atrium
CONDUCTION SYSTEM
1% of cardiac muscle generate action potentials= Pacemaker & Conduction system
Normally begins at sinoatrial (SA) node Atria & atria contractAV node -slowsAV bundle (Bundle of His) bundle branches Purkinje fibers apex and up- then ventricles
contract
PACEMAKER
Depolarize spontaneouslysinoatrial node ~100times /minalso AV node ~40-60 times/minin ventricle ~20-35 /minFastest 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 depolarizationContraction begins right after peakRepolarization is masked in QRSQRS complex= Ventricular
depolarizationContraction of ventricleT-wave = ventricular repolarizationJust after ventricles relax
FIGURE 15.7
CARDIAC CYCLE
after T-wave ventricular diastoleVentricular pressure drops below atrial & AV valves open ventricular filling occurs
After P-wave atrial systoleFinishes filling ventricle (`25%)
After QRS ventricular systolePressure pushes AV valves closedPushes semilunar valves open and ejection occurs
Ejection until ventricle relaxes enough for arterial pressure to close semilunar valves
ACTION POTENTIAL
Review muscleHeart 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 nervesCardiovascular center in Medulla
parasympathetic- ACh slowsVia vagus nerve
Sympathetic - norepinephrine speedsSensory 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 tachycardiaIonsIncreased 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