The Cardiovascular system: Heart 19 Chapter 11 Pages 356-397

Chapter 11 Wordbytes Angio-, vascul- = vessel Auri- = ear Brady- = slow Cardio-, coron- = heart -emia = in the blood Endo- = within Epi = on top of Hemangi-= blood vessel Ische- = to obstruct Myo- = muscle Papill- = nipple Phleb- = vein Peri = around Pulmon- = lung Sphygm- = pulse Tend- = tendon Thromb- = blood clot Ventr- =underside

Size, Location, Orientation About the size of a fist; weighs less than a pound Found in thoracic cavity between two lungs = mediastinum (medial cavity of thorax) ~2/3 to left of midline Surrounded by pericardium: Fibrous pericardium- Inelastic; protects 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.

Homeostatic Imbalance p.683 Pericarditis  inflammation of pericardium Creates a creaking sound heard by a stethoscope Can compress fluid and limit heart’s ability to pump blood

p. 682 Figure 15.1

3 Heart Wall Layers: p. 684 1. Epicardium- outer layer (contains fat) 2. Myocardium- cardiac muscle = bulk of heart; what contracts Two separate networks via gap junctions in intercalated discs- atrial & ventricular Networks- contract as a unit 3. Endocardium- Squamous epithelium Lines inside of myocardium

Figure 15.2a

Figure 15.2b

Figure 15.2c

4 Chambers of Heart 2 superior chambers= atria (receiving chambers) Contains auricles small, wrinkled, protruding appendages 2 Parts: 1.smooth-walled posterior 2.anterior = ridged by bundles of muscles Between is interatrial septum Contains fossa ovalis- remnant of foramen ovalis (opening in fetal heart)

Blood enters right atria via 3 veins: Superior vena cava (from body regions superior to diaphragm) Inferior vena cava (from body areas below diaphragm) Coronary sinus (collects blood from myocardium)

4 pulmonary veins enter the left atrium Transport blood from the lungs back to the heart

2 inferior chambers = ventricles (discharging chambers = pumps) Make up most of the mass of the heart Between is interventricular septum Right ventricle pumps blood into the pulmonary trunk (to lungs for gas exchange) Left ventricle pumps blood into the aorta = largest artery in the body Wall thickness depends on work load Atria thinnest Right ventricle pumps to lungs & thinner than left

Great Vessels Of Heart- Right p. 687 Superior & inferior Vena Cavae Delivers deoxygenated blood to R. atrium from body Coronary sinus drains heart muscle veins R. Atrium  R. Ventricle pumps through Pulmonary Trunk R & L pulmonary arteries  lungs

Great Vessels –Left p. 687-8 Pulmonary Veins from lungs oxygenated blood L. atrium Left ventricle ascending aorta body Between pulmonary trunk & aortic arch is ligamentum arteriosum fetal ductus arteriosum remnant

p. 685 - 687 Figure 15.3a

p. 685 - 687 Figure 15.3b

p. 685 - 687 Figure 15.3c

Blood Supply Of Heart Blood flow through vessels in myocardium = coronary circulation L. & R. coronary arteries branch from aorta branch to carry blood throughout muscle Deoxygenated blood collected by Coronary Sinus (posterior) Empties into R. Atrium

Figure 15.5a

p. 688 Figure 15.5b

Valves p.690 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 Chordae tendineae – “heart strings” = anchor cusps to muscles Semilunar valves near origin of aorta & pulmonary trunk Aortic & pulmonary (semilunar) valves respectively

p. 691 Figure 15.4ab

p. 691 Figure 15.4c

p. 691 Figure 15.4d

Properties of Cardiac Muscle Striated Contracts by sliding Short, fat, branched, interconnected Contains 1 or 2 centrally located nuclei Large mitochondria = high resistance to fatigue

Conduction System 1% of cardiac muscle generate action potentials= Pacemaker & Conduction system Normally begins at sinoatrial (SA) node Atria contracts 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 Epinephrine & norepinephrine increase H.R. 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