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Transcript
Circulatory System: the Heart. The heart Chapter 19 pgs 715-743 History • Aristotle thought the heart was the seat of emotion • Not until Vesalius’ dissections did Western science correct its mistakes • Eastern scientists had it right all along Confucius say western science needs some work - I am right and a genius. Plato was my teacher and Medieval Scholars love me. Snap! - No, you are dead and wrong. I am the dissection King of the Sixteenth Century. Booyah! Overview • Cardiovascular system = heart and vessels, not blood • Arteries = away from heart • Veins = toward heart • Capillaries = small vessels that connect arteries and veins Two major divisions • Pulmonary circuit takes blood to lungs for gas exchange • Systemic circuit takes oxygen rich blood to the organs • Right side of heart gets O2 poor blood – Pulmonary artery takes it away from heart to lungs – Pulmonary veins bring it back O2 rich • Left side of heart serves systemic system – Aorta takes O2 rich blood out to organs – Superior vena cava brings it back from head, neck, upper limbs – Inferior vena cava brings it back from organs below diaphragm. Where is your heart? • 2/3s of it lies to the left of the median plane • Adult heart 9 cm wide at base, 13 cm long, 6 cm deep • Weighs 300 g (10 oz) Pericardium • Double walled sac enclosing heart • In the pericardial cavity is pericardial fluid that allows the heart to beat without friction • Pericarditis is the pain when the membranes are dry Heart wall 3 layers • Epicardium – outer layer – Fatty • Myocardium – Thickest layer – Cardiac muscle that pulls against a fibrous skeleton of fibers – Focuses the movement of electricity • Endocardium – Smooth inner lining Chambers • Superiorly; Right and Left atria receive returning blood – Have an easier workload • Inferiorly; Right and Left ventricles eject blood Valves • Ensure one way flow • Made of flaps called cusps • Open & Close as a result of pressure changes • When ventricles relax valves are open • Full ventricles contract pressure pushes valves shut Coronary Circulation • Getting blood to your heart • ~3 bil beats over an 80 year life • Needs 5% of bodies O2 – Coronary artery delivers this • Myocardial Infarction: fat deposits blocking arteries leading to necrosis of tissue – Anastomoses: our bodies defense • Two arteries covering the same area Cardiac Surgery Incision and Cannulation A Cannula is a flexible tube The collar bones, angle and tip of the breast bone (sternum) guide the surgeon in making the incision Cardiac Surgery Incision and Cannulation The sternum is opened with a saw (sternotomy) Cardiac Surgery Incision and Cannulation During this operation, the tissues were covered with towels soaked in anti-septic solution. The breast bone is spread with a retractor. Plastic tubes are placed into the major artery (aorta) Cardiac Surgery Incision and Cannulation and receiving chamber of the heart (right atrium) Cardiac Surgery Incision and Cannulation These tubes are connected to the heart lung bypass machine (pump) which supports the patient's life while the heart is stopped during the surgery. The surgeon is assisted by a large team while performing the surgery Cardiac Surgery Incision and Cannulation At the end of the surgery, the plastic tubes are removed after the heart lung bypass machine is turned off. The sternum is closed with heavy gauge wires and the chest is closed in layers of sutures Aerobic vs. Anaerobic • AAerobic activity = increases heartrate to at least 65% of it's maximum for an extended period of time. – • Best for cardiovascular strength, endurance and fat burning Anaerobic activity = activity done in intense, short bursts (weight lifting, sprinting, calisthenics, etc.) – fuel used during anaerobic activity is glucose and glycogens (sugars that are stored in our bodies). – Best for strength training and body sculpting. • Aerobic activity should be the predominant exercise for good general health. Cardiac Muscle and The Cardiac Conduction System • Cardiocytes: short, thick branched cells – Sarcoplasmic reticulum is less developed, but T-Tubules are more developed, lots of mitochondria – Do very little mitosis • Intercalated discs join cells end to end – Gap junctions allow ions to flow between cells, keeping electrical current Cardiac conduction system • We’re myogenic: the signal for the heart to beat comes from within the heart itself • Our brain can modify the heartbeat, but not create it. Disembodied hearts can beat for hours. • Sinoatrial (SA) node = the pacemaker • Atrioventricular node = sends signals to the ventricles Electrical & Contractile activity • Contraction = systole • Relaxation = diastole – These can apply to parts, or just ventricles • Sinus rhythm = normal beat – Can have ectopic focus (alternate source of beat, instead of SA node) called nodal rhythm • Arrhythmia = abnormal rhythm Physiology of the SA node • The nerves of the SA node are always slowly moving toward an action potential • So as soon as the heart beats its already starting toward another beat • ~75 beats per minute • Cardiac muscle has a sustained contraction, and a longer refratcory period – This prevents tetanus: Continual contraction Electrocardiogram(ECG/EKG) • Composite reading of many action potentials • P wave: atria contract • QRS complex: AV node fires, ventricles start to contract • T wave: ventricles repolarizing Cardiac cycle Now, can you… • Describe the relationship of the heart to other thoracic structures? • Identify the chambers and valves • Trace the flow of blood through the heart chambers • Contrast cardiac vs. skeletal muscle • Describe the physiological properties of cardiac muscle • Describe the heart’s electrical conduction system