Ch 22B - Kelli Teager PDF

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Kelli Teager...

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the heart: coronary circulation & conduction system the coronary circulation overview - the heart does not use the blood within its chambers for its own needs - coronary circulation: - coronary arteries - coronary veins coronary arteries - the right & left coronary arteries travel within the coronary sulcus & supply heart wall w/ oxygen & nutrients - branch off ascending aorta just superior to aortic semilunar valve right coronary artery - right coronary artery branches into: - right marginal artery: supplies the right border of the heart - posterior interventricular artery: supplies posterior surfaces of the left & right ventricles left coronary artery - left coronary artery branches into: - anterior interventricular artery (left anterior descending artery): anterior surface of ventricles, interventricular septum - circumflex artery: left atrium & ventricle coronary veins - venous return of blood from the heart wall occurs through 3 major veins: 1. great cardiac vein 2. middle cardiac vein 3. small cardiac vein - major cardiac veins drain into coronary sinus, which drains into the right atrium 1. great cardiac vein: runs alongside anterior interventricular artery 2. middle cardiac vein: runs alongside posterior interventricular artery 3. small cardiac vein: travels close to the right marginal artery

ch 22B

effects of atherosclerosis - coronary artery disease: atherosclerosis of the coronary arteries - fatty plaque formation decreases blood supply to the myocardium - results in diminished heart function - may cause angina pectoris (chest pain) - risk factors - high BP, smoking, high cholesterol levels, diabetes, inactivity & family history - treatment - medication, changes in diet & exercise myocardial infarction (MI)/“heart attack” - death of cardiac muscle cells & the resulting failure of the heart to deliver enough blood to the rest of the body - usually follow occlusion of coronary arteries - non-contracting scar tissue may start to form - may be sudden onset b/c of the buildup of plaque (lipids) on the lining of the arteries (atherosclerosis) is asymptomatic - lifestyle changes can reduce the risk of heart disease - exercise - diet: decrease fat & cholesterol intake & increase fruit & vegetable consumption - don’t smoke - treatment to heart disease pateints - clot dissolving enzymes - coronary artery bypass surgery - angioplasty, laser surgery to open constricted coronary arteries how the heart beats cardiac conduction system - heart exhibits autorythmicity - it initiates its own heartbeats - the conducting system consists of specialized cells that start & propagate electrical impulses to myocardial (contractile) cells cardiac conduction system: SA node - electrical impulses begins at the sinoatrial (SA) node (pacemaker) - septs the normal rate of contraction, about every 0.85 s

cardiac conduction system: AV node - to left atrium & atrioventricular (AV) node on the floor of right atrium

cardiac conduction system: ventricles - impulse -> atrioventricular (AV) bundle (bundle of His), extending into interventricular septum -> left & right bundles (bundle branches) -> purkinje fibers (begin at the heart apex) -> impulse spreads from the apex to all of the ventricular myocardium

cardiac conduction system: electrocardiogram - electrocardiogram (ECG/EKG) is a graph printout of electrical activity across the cardiac conduction system - P wave - atrial depolarization - QRS complex - ventricular depolarization - atrial depolarization - T wave - ventricular repolarization cardiac conduction system: pacemakers - if the cardiac conduction system doesn’t function correctly, an artificial pacemaker can be implanted next to the heart - provides a regular electrical signal to trigger the beat

trying it all together: the cardiac cycle - a cardiac cycle is the time from the start of one heartbeat to the start of the next - the cardiac cycle induces both contraction & relaxation phases - contraction of a chamber is called systole - generates pressure to move blood - relaxation of a chamber is called diastole - allows chamber to fil with blood prior to the next contraction - lasts about .85 sec - 3 stages: - stage 1: both semilunar valves are closed (“dub”), both cuspid valves are open - atria contract - ventricles relax & receive blood from the atria - if the heart beats about 70 times/min, systole of the atria lasts about .15 sec - stage 2: both cuspid valves close (“lub”) semilunar valves open - ventricles contract - blood is pushed out of the ventricles - systole of the ventricles lasts about .3 sec - stage 3: both semilunar valves close, both cuspid valves open, all chambers fil with blood - when the atria contract, the ventricles are in diastole - when the ventricles contract, the atria are in diastole - then diastole of both atria & both ventricles occurs at the same time — lasts about .40 sec summary

blood flow through the heart

development of the heart - foramen ovale - opening btw the 2 atria - allows some blood to bypass lungs before birth - flap closes over the opening & grows to the adjoining tissue at birth - ductus arteriosus - artery btwn right pulmonary artery & aortic arch - serves as a bypass for blood from lungs to systemic circulation - at birth, a muscular layer of the artery goes into permanent spastic contraction & all of the tissue is replaced w/ CT...