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Cardiovascular System 2

Explore the three circuits of the cardiovascular system - systemic, pulmonary, and coronary - and learn about the heart's conducting system, electrocardiogram, cardiac arrhythmias, cardiac cycle, heart sounds, and regulation of the heart. Discover the effects of aging on heart function.

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Cardiovascular System 2

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  1. Cardiovascular System 2

  2. Circuits of the Blood There are 3 circuits: • Systemic Circulation • From the left ventricle to the aorta and on to the body • Back to the heart via the superior and inferior vena cava to the right atrium • Pulmonary Circulation • From right ventricle to the pulmonary trunk, on to the pulmonary (left and right) arteries and to the lungs • Back to the heart via the (left and right) pulmonary veins • Cardiac/Coronary Circulation • Supply needs of the heart itself • Arteries go to the heart branching off of the aorta • Valveless veins return to directly to the right atrium

  3. Systemic and PulmonaryCirculation

  4. Heart Skeleton • Consists of plate of fibrous connective tissue between atria and ventricles • Fibrous rings around valves to support • Serves as electrical insulation between atria and ventricles • Provides site for muscle attachment

  5. Conducting System of Heart

  6. Electrical Properties • Resting membrane potential (RMP) present • Action potentials • Rapid depolarization followed by rapid, partial early repolarization. Prolonged period of slow repolarization which is plateau phase and a rapid final repolarization phase • Voltage-gated channels

  7. Action Potentials inSkeletal and Cardiac Muscle

  8. SA Node Action Potential

  9. Refractory Period • Absolute: Cardiac muscle cell completely insensitive to further stimulation • Relative: Cell exhibits reduced sensitivity to additional stimulation • Long refractory period prevents tetanic contractions

  10. Electrocardiogram • Action potentials through myocardium during cardiac cycle produces electric currents than can be measured • Pattern • P wave • Atria depolarization • QRS complex • Ventricle depolarization • Atria repolarization • T wave: • Ventricle repolarization

  11. Cardiac Arrhythmias • Tachycardia: Heart rate in excess of 100bpm • Bradycardia: Heart rate less than 60 bpm • Sinus arrhythmia: Heart rate varies 5% during respiratory cycle and up to 30% during deep respiration • Premature atrial contractions: Occasional shortened intervals between one contraction and succeeding, frequently occurs in healthy people

  12. Alterations in Electrocardiogram

  13. Cardiac Cycle • Heart is two pumps that work together, right and left half • Repetitive contraction (systole) and relaxation (diastole) of heart chambers • Blood moves through circulatory system from areas of higher to lower pressure. • Contraction of heart produces the pressure

  14. Cardiac Cycle

  15. Events during Cardiac Cycle

  16. Heart Sounds • First heart sound or “lubb” • Atrioventricular valves and surrounding fluid vibrations as valves close at beginning of ventricular systole • Second heart sound or “dupp” • Results from closure of aortic and pulmonary semilunar valves at beginning of ventricular diastole, lasts longer • Third heart sound (occasional) • Caused by turbulent blood flow into ventricles and detected near end of first one-third of diastole

  17. Location of Heart Valves

  18. Mean Arterial Pressure (MAP) • Average blood pressure in aorta • MAP=CO x PR • CO is amount of blood pumped by heart per minute • CO=SV x HR • SV: Stroke volume of blood pumped during each heart beat • HR: Heart rate or number of times heart beats per minute • Cardiac reserve: Difference between CO at rest and maximum CO • PR is total resistance against which blood must be pumped

  19. Factors Affecting MAP

  20. Regulation of the Heart • Intrinsic regulation: Results from normal functional characteristics, not on neural or hormonal regulation • Starling’s law of the heart • Extrinsic regulation: Involves neural and hormonal control • Parasympathetic stimulation • Supplied by vagus nerve, decreases heart rate, acetylcholine secreted • Sympathetic stimulation • Supplied by cardiac nerves, increases heart rate and force of contraction, epinephrine and norepinephrine released

  21. Heart Homeostasis • Effect of blood pressure • Baroreceptors monitor blood pressure • Effect of pH, carbon dioxide, oxygen • Chemoreceptors monitor • Effect of extracellular ion concentration • Increase or decrease in extracellular K+ decreases heart rate • Effect of body temperature • Heart rate increases when body temperature increases, heart rate decreases when body temperature decreases

  22. Baroreceptor and ChemoreceptorReflexes

  23. Effects of Aging on the Heart • Gradual changes in heart function, minor under resting condition, more significant during exercise • Hypertrophy of left ventricle • Maximum heart rate decreases • Increased tendency for valves to function abnormally and arrhythmias to occur • Increased oxygen consumption required to pump same amount of blood

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