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Anatomy and Physiology

Anatomy and Physiology. Chapter 20: The Heart. Introduction . Heart beat 100,000X / day ( moves 8000L) Muscle is never at rest Pulmonary circuit goes to heart from lungs Systemic circuit goes to heart from body Arteries (afferent) – away from the heart Veins (efferent) – toward the heart

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Anatomy and Physiology

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  1. Anatomy and Physiology Chapter 20: The Heart

  2. Introduction • Heart beat 100,000X / day ( moves 8000L) • Muscle is never at rest • Pulmonary circuit goes to heart from lungs • Systemic circuit goes to heart from body • Arteries (afferent) – away from the heart • Veins (efferent) – toward the heart • Capillaries – exchange vessels

  3. 20.1 Anatomy of the Heart • Tilts to left of sternum • Between intercostal spaces 3 and 5 • Associated with lots of fatty tissue • Pericardial sac – protects and lubricates (fluid) • Myocardium = heart muscle • Coronary arteries = supply blood to heart muscle itself ( these are “bypassed”)

  4. Chambers and vessels • Superior vena cava – blood from head/neck/limbs to RA • Right Atrium – receives blood from body • Right ventricle – pump * / to lungs • Left Atrium– from lungs • Left ventricle – pump * / to body through; thicker more muscular side… to whole body • Aorta • Inferior vena cava – receives blood from the trunk to RA • * RV and LV pump at same time, same amount

  5. Chambers, vessels and valves • RA and RV separated by tricuspid valve • Cusps anchored to chordae tendineae that tug flaps down to prevent backflow • LA receives blood through mitral valve • LV is associated with semilunar valve

  6. 20.2 Generation of Action Potentials • Muscle cells in conducting system coordinate beat • Contractile cells contract to propel blood • Electrocardiograph (ECG, EKG) shows electrical events of heart beat • App called cardiograph

  7. Sinoatrial (SA) node in RA • Spontaneous depolarization without neural or hormonal • 80 – 100 action potentials per minute • Pacemaker cells • Atrioventricular (AV) node between A and V • 50 msec from SA to AV • Delay at AV node so atria finish contracting before ventricles • Conducting cells with internodal pathways do not have stable resting potential; drift toward threshold • Purkinje fibers • Rapid conduction of action potentials ventricular myocardium

  8. Energy • Heart muscles have lots of mitochondria that break down both fatty acids and glucose (stored as glycogen) • Have heme units (part of hemoglobin) stored as myoglobin so they can have access to lots of O2 – very aerobic • Calcium ions are very important to the conduction of action potentials in the cardiac muscle cells

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