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THE HEART

THE CIRCULATORY SYSTEM:. THE HEART. THE HEART. THE HEART. THE HEART. THE HEART. THE HEART. THE HEART. HEART LOCATION & ANATOMY. left lung. right lung. pericardium. apex of heart. diaphragm. MEDIASTINUM. PERICARDIAL LAYERS. pericardial cavity. FIBROUS PERICARDIUM.

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THE HEART

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  1. THE CIRCULATORY SYSTEM: THE HEART THE HEART THE HEART THE HEART THE HEART THE HEART THE HEART

  2. HEART LOCATION & ANATOMY left lung right lung pericardium apex of heart diaphragm MEDIASTINUM

  3. PERICARDIAL LAYERS pericardial cavity FIBROUS PERICARDIUM SEROUS PERICARDIUM (parietal layer) SEROUS PERICARDIUM visceral layer (epicardium) myocardium endocardium heart chamber

  4. HEART MUSCLE • Three Layers • Endocardium • Myocardium • Epicardium cardiac muscle bundles

  5. HEART CHAMBERS Left atrium Right atrium ANTERIOR Left ventricle Right ventricle Interventricular septum INTERIOR

  6. HEART CHAMBERS: ATRIA fossa ovalis (L) pulmonary veins pectinate muscles bicuspid valve tricuspid valve

  7. HEART CHAMBERS: VENTRICLES aorta aortic semilunar valve pulmonary semilunar valve chordae tendineae trabeculae carneae papillary muscles

  8. PULMONARY AND SYSTEMIC CIRCULATION

  9. CIRCULATION THROUGH THE HEART Vena cavae (R) ATRIUM (R) VENTRICLE Pulmonary trunk Pulmonary arteries LUNGS Pulmonary veins (L) ATRIUM Aorta (L) VENTRICLE

  10. CORONARY CIRCULATION (L) coronary artery circumflex artery (R) coronary artery marginal artery posterior interventricular artery anterior interventricular artery

  11. CORONARY CIRCULATION great cardiac vein anterior cardiac veins coronary sinus middle cardiac vein small cardiac vein

  12. CORONARY CIRCULATION SUMMARY Aorta (R)Coronary artery (L)Coronary artery Posterior interventricular artery Anterior interventricular artery Circumflex artery Marginal artery Walls of (R) atrium & (R) ventricle Walls of (L) atrium & (L) ventricle Ventricular walls Ventricular walls Cardiac veins Coronary sinus (R)atrium

  13. CARDIAC HISTOLOGY • Cardiac Muscle Cells • Striated • 1 to 2 nuclei • Numerous, large mitochondria • Intercalated discs

  14. CARDIAC CONDUCTION SYSTEM • Nodal System • Autorhythmic Cells • 1% of cardiac cells • Initiate and conduct and impulse • Unstable resting membrane potential • Continuously depolarize • Trigger contractions of heart muscle

  15. CARDIAC CONDUCTION SYSTEM • Nodal System • Sinoatrial (SA) Node • Mass of autorhythmic cells • Near SVC entrance • Depolarizes 70 to 80 times a minute (100 if no neural control) • Depolarization spreads through atria • Atria contract

  16. CARDIAC CONDUCTION SYSTEM • Nodal System • Atrioventricular (AV) Node • Autorhythmic cells • Above tricuspid valve in interatrial septum • Passes impulse on to AV bundle (Bundle of His) • Bundle of His (AV Bundle) • Conducts impulse to right and left bundle branches

  17. CARDIAC CONDUCTION SYSTEM • Nodal System • Bundle Branches • Right and left branches • Branch into purkinje fibers • Purkinje Fibers • Enter myocardium of ventricle walls and papillary muscles • Carry impulse to ventricles • Ventricular contraction

  18. CARDIAC CONDUCTION SYSTEM SUMMARY Sinoatrial Node AV Node AV Bundle Bundle Branches Purkinje Fibers

  19. EXTRINSIC INNERVATION • Autonomic Nervous System • Can slow or accelerate heart • Cannot initiate a contraction • Cardiac centers in medulla • Stimulation by sympathetic neurons • Increase heart rate • Increase force of contraction • Inhibition by parasympathetic neurons • Via Vagus nerve • Decrease heart rate • Decrease force of contraction

  20. CARDIAC CYCLE • Interval from end of one contraction to the following contraction • 0.8 sec. • Consists of Two Phases: • Systole phase • Diastole phase

  21. CARDIAC CYCLE semilunar valves (closed) • Systole Phase • Contraction phase • Blood ejected • Atrial Systole (0.1 sec.) • Following passive filling with blood • AV valves open, semilunar valves closed • Ventricles fill with blood LA bicuspid (open) RA LV tricuspid (open) RV

  22. CARDIAC CYCLE semilunar valves (open) • Systole Phase (cont.) • Ventricular Systole (0.3 sec.) • AV and semilunar valves closed until pressure opens semilunar valves • Blood pushed into pulmonary trunk • 120 mm Hg pressure • Atria in diastole LA bicuspid (closed) RA LV tricuspid (closed) RV

  23. CARDIAC CYCLE semilunar valves (closed) • Diastole Phase • Relaxation phase • Ventricular Diastole • Follows ventricular systole • AV valves reopen and filling begins • 80 mm Hg pressure LA bicuspid (open) RA LV tricuspid (open) RV

  24. ELECTRICAL EVENTS: ECG QRS complex P wave: atrial depolarization QRS complex: ventricular depolarization T wave: ventricular repolarization

  25. ECG READINGS 2nd Degree Heart Block (more P waves) Normal SA Node Dysfunction no P waves Ventricular Fibrillation

  26. HEART SOUNDS • Lub-dub • AV valves closing for ventricular systole • Semilunar valves closing • Pause • Quiescent period (0.4 sec.) • Ventricles and atria in diastole simultaneously

  27. CARDIAC OUTPUT • Amount of blood pumped out by each ventricle in 1 minute • Sympathetic stimulation needed if CO more than 14 liters/min. is needed • Starling’s Law • The greater the volume of blood returned to the heart by the veins, the greater the volume of blood the heart will pump

  28. HEART RATE REGULATION: Nervous System • Cardiac Inhibitory Center • Medulla • Parasympathetic • Vagus nerve • Continually slows heart to maintain average of 70 beats/min. • Cardiac Accelerator Center • Medulla • Sympathetic • Increases heart rate and force of contraction when needed

  29. OTHER REGULATORS • Hormonal Regulation • Accelerators • Epinephrine, norepinephrine • Thyroxine, T3 • Body Temperature • Increase temp. = increase heart rate • Decrease temp.= decrease heart rate • Baroreceptors • Carotid sinus and aortic arch • Stretch  impulses to inhibitory center vagus nerve  decreased heart rate • Bainbridge (Atrial) Baroreceptors • Measure intraatrial pressure • Stimulate accelerator center • Increased heart rate and force of contraction

  30. DISORDERS • Tachycardia • Abnormally high heart rate (over 100) • Bradycardia • Abnormally low heart rate (under 60) • Myocardial Infarction • Death of myocardium • Replaced with scar tissue • Arrhythmia • Uncoordinated pattern of heart contractions • Fibrillation • Rapid and out of phase contractions • Angina Pectoris • Pain caused by deficiency in blood delivery to the myocardium

  31. DISORDERS • Pericarditis • Inflammation of the pericardium • Can result in cardiac tamponade • Congestive Heart Failure • Inadequate pumping of the heart • Blood back-up in lungs or body • Excessive fluid in tissues • Atherosclerosis • Formation of fatty plaque on artery walls • Decrease in vessel elasticity and possible blockage • Ischemic Heart Disease • Inadequate blood supply to cardiac muscle • Temporary or chronic • Heart Murmur • Defective valve allowing back flow of blood • Hissing sound from turbulence

  32. THE CIRCULATORY SYSTEM: VESSELS BLOOD

  33. BLOOD VESSELS: ARTERIES • Arteries • Carry blood away from heart • high in oxygen • Branch into arterioles • Three groups: • Elastic Arteries • Largest • Elastic fibers in tunica media • Expand and recoil (pulse) • Examples: • Aorta, pulmonary trunk, common iliac arteries

  34. BLOOD VESSELS: ARTERIES • Three groups (cont.) • Muscular arteries • Medium size • Carry blood from elastic arteries to arterioles • Active in vasoconstriction • Examples: • Femoral, brachial, axillary arteries • Arterioles • Smallest arteries • Carry blood to capillaries • Regulate blood flow to capillaries

  35. BLOOD VESSELS: VEINS • Carry blood from body back to heart • Low in oxygen • Venulesempty into veins Valve (open) • May contain valves Valve (closed)

  36. OTHER VESSELS • Capillaries • Smallest vessels • Connect arterioles to venules • Exchange of nutrients, gases with tissue cells • Sinusoids • Vessels in place of capillaries • In liver, spleen, bone marrow • Anastomoses • Connections between vessels such as arteries and veins without a capillary bed in between

  37. STRUCTURE OF BLOOD VESSELS • Arteries and Veins • Three tunics • Tunica interna (intima) • Tunica media • Tunica externa (adventitia) tunica interna • Vasa vasorum tunica media tunica externa ARTERY VEIN

  38. STRUCTURE OF BLOOD VESSELS • Capillaries • Thin walls • Pre-capillary sphincters ARTERIOLE smooth muscle cell endothelium CAPILLARY

  39. CAPILLARY STRUCTURE Pre-capillary sphincters TERMINAL ARTERIOLE POSTCAPILLARY VENULE CAPILLARIES

  40. BLOOD PRESSURE • Pressure exerted on vessel walls • mm Hg pressure in systemic arteries • Measured with sphygmomanometer • Pressure in cuff compresses artery until no pulse heard • Systolic pressure: taken at first pulse as pressure in cuff released (ave. 120) = pressure while heart ventricles contracting • Diastolic pressure: taken when cuff released to point where sound no longer audible (ave. 80) = pressure when ventricles not contracting • Pulse pressure = systolic - diastolic (measure of stress exerted on small arteries)

  41. INFLUENCES ON B.P. • Blood Pressure varies directly with the following: • Cardiac Output • Stroke volume X heart rate • Normal is 5.5 liters/min. • Peripheral Resistance • Opposition to blood flow •  with blood viscosity •  with length of vessel •  with  in vessel diameter (has the greatest influence on B.P.)

  42. INFLUENCES ON B.P. • Blood Pressure varies directly with the following: • Blood Volume • Mainly regulated by kidneys •  in blood volume =  in B.P. •  in blood vol. =  decrease in B.P.

  43. REGULATION OF B.P. • By nervous system, kidneys and chemical controls • Nervous Regulation: • Sympathetic nerve fibers • Vasoconstriction of blood vessels •  diameter,  resistance  B.P. • Vasomotor center in medulla • Controls cardiac output • Controls degree of vessel constriction

  44. REGULATION OF B.P. • Nervous Regulation (cont.) • Baroreceptors • Pressure sensitive mechanoreceptors • In aortic arch, carotid sinuses, large elastic arteries of head and thorax • Stretching impulses to vasomotor center • Vasomotor center inhibited  dilation of vessels, decreased heart rate and output  decreased B.P. • Chemoreceptors • Monitor O2, CO2 levels and pH of blood • In carotid and aortic bodies • Send impulses to vasomotor center if O2 or pH drop or CO2 rises • Vasoconstriction  B.P.

  45. CHEMICAL REGULATION OF B.P. • Epinephrine and Norepinephrine • Vasoconstriction •  cardiac output • ANF (Atrial Natriuretic Factor) • Release of more sodium and water in urine •  blood volume  B.P. • ADH (Antidiuretic Hormone) • Stimulates kidneys to reabsorb water •  blood volume  B.P. • Renin • Released from kidneys in response to low B.P. • Stimulates angiotensin/aldosterone system • Kidneys reabsorb sodium and water  blood volume and B.P.

  46. RENIN / ANGIOTENSIN / ALDOSTERONE SYSTEM

  47. CHEMICAL REGULATION OF B.P. • Other Chemical Controls: • Endothelin • Nitric oxide • Inflammatory chemicals (histamine) • Alcohol (inhibits ADH release and depresses the vasomotor center)

  48. RENAL REGULATION OF B.P. • Kidneys may alter B.P. directly • Increased B.P. more blood filtered by kidneys • More urine produced and released •  blood volume  B.P. • Kidneys may alter B.P. indirectly • Renin/angiotensin system activated with  B.P. • Vasoconstriction, water reabsorption due to aldosterone release •  blood volume  B.P.

  49. DISORDERS • Hypotension • Low B.P. (systolic below 100 mm Hg) • Aging, poor nutrition, anemia, hypothyroidism, Addision’s disease, low blood protein levels or circulatory shock

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