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CARDIOVASCULAR PHYSIOLOGY

CARDIOVASCULAR PHYSIOLOGY

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CARDIOVASCULAR PHYSIOLOGY

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  1. CARDIOVASCULAR PHYSIOLOGY Dr. Poland Room 3-007, Sanger Hall Phone: 828-9557 E-mail: poland@hsc.vcu.edu

  2. HEART (PUMP) AUTOREGULATION CARDIOVASCULAR SYSTEM NEURAL REGULATION HORMONAL VESSELS (DISTRIBUTION SYSTEM) RENAL-BODY FLUID CONTROL SYSTEM

  3. PULMONARY CIRCULATION 1. LOW RESISTANCE 2. LOW PRESSURE (25/10 mmHg) SYSTEMIC CIRCULATION 1. HIGH RESISTANCE 2. HIGH PRESSURE (120/80 mmHg) PARALLEL SUBCIRCUITS UNIDIRECTIONAL FLOW

  4. ARTERIES (LOW COMPLIANCE) HEART DIASTOLE VEINS CAPACITY VESSELS 80 mmHg 120 mmHg SYSTOLE CAPILLARIES

  5. THE SYSTEMIC CIRCULATION CAPACITY VESSELS

  6. NORMAL

  7. AUTOMATICITY Na+ K+ Gradually increasing PNa K+ Na+ -0 -70 mV THRESHOLD RESTING

  8. Atrio-ventricular (AV) node Sino-atrial (SA) node BUNDLE BRANCHES PURKINJE FIBERS

  9. INTERCALATED DISC (TIGHT JUNCTION)

  10. PACEMAKERS (in order of their inherent rhythm) • Sino-atrial (SA) node • Atrio-ventricular (AV) node • Bundle of His • Bundle branches • Purkinje fibers

  11. PHASE Mechanical Response 0 = Rapid Depolarization (inward Na+ current) 1 1 = Overshoot 2 0 2 = Plateau (inward Ca++ current) 3 = Repolarization (outward K+ current) 0 MEMBRANE POTENTIAL (mV) 4 = Resting Potential 3 4 -90 TIME

  12. ACTION POTENTIALS VENTRICULULAR CELL SAN 1 2 0 0 0 3 0 3 4 -50 -50 MEMBRANE POTENTIAL (mV) 4 -100 -100

  13. SINGLE VENTRICULAR ACTION POTENTIAL ENDOCARDIAL FIBER ATRIAL FIBER EPICARDIAL FIBER R 1 mV ECG T P Repolarization of ventricles Q S Depolarization of ventricles Depolarization of atria

  14. ECG Recordings (QRS Vector pointing leftward, inferiorly & posteriorly) 3 Bipolar Limb Leads: RA LA I = RA vs. LA (+) LL

  15. ECG Recordings (QRS Vector pointing leftward, inferiorly & posteriorly) 3 Bipolar Limb Leads: RA LA I = RA vs. LA (+) II = RA vs. LL (+) LL

  16. ECG Recordings (QRS Vector pointing leftward, inferiorly & posteriorly) 3 Bipolar Limb Leads: RA LA I = RA vs. LA (+) II = RA vs. LL (+) III = LA vs. LL (+) LL

  17. ECG Recordings (QRS Vector pointing leftward, inferiorly & posteriorly) 3 Bipolar Limb Leads: RA LA I = RA vs. LA (+) II = RA vs. LL (+) III = LA vs. LL (+) 3 Augmented Limb Leads: LL aVR = (LA-LL) vs. RA(+)

  18. ECG Recordings (QRS Vector pointing leftward, inferiorly & posteriorly) 3 Bipolar Limb Leads: RA LA I = RA vs. LA (+) II = RA vs. LL (+) III = LA vs. LL (+) 3 Augmented Limb Leads: LL aVR = (LA-LL) vs. RA(+) aVL = (RA-LL) vs. LA(+)

  19. ECG Recordings (QRS Vector pointing leftward, inferiorly & posteriorly) 3 Bipolar Limb Leads: RA LA I = RA vs. LA (+) II = RA vs. LL (+) III = LA vs. LL (+) 3 Augmented Limb Leads: LL aVR = (LA-LL) vs. RA(+) aVL = (RA-LL) vs. LA(+) aVF = (RA-LA) vs. LL(+)

  20. 6 PRECORDIAL (CHEST) LEADS Spine V6 V5 Sternum V4 V3 V1 V2

  21. ECG Recordings: (QRS vector---leftward, inferiorly and posteriorly 3 Bipolar Limb Leads I = RA vs. LA(+) II = RA vs. LL(+) III = LA vs. LL(+) 3 Augmented Limb Leads aVR = (LA-LL) vs. RA(+) aVL = (RA-LL) vs. LA(+) aVF = (RA-LA) vs. LL(+) 6 Precordial (Chest) Leads: Indifferent electrode (RA-LA-LL) vs. chest lead moved from position V1 through position V6.

  22. THE CARDIAC CYCLE LATE DIASTOLE DIASTOLE ISOMETRIC VENTRICULAR RELAXATION ATRIAL SYSTOLE VENTRICULAR EJECTION ISOMETRIC VENTRICULAR CONTRACTION

  23. EJECTION ISOVOLUMETRIC CONTRACTION ISOVOLUMETRIC RELAXATION RAPID INFLOW DIASTASIS ATRIAL SYSTOLE AORTIC PRESSURE PRESSURE (mmHg) ATRIAL PRESSURE VENTRICLE PRESSURE VOLUME (ml) ECG PHONO- CARDIOGAM SYSTOLE DIASTOLE SYSTOLE

  24. MEASUREMENT OF CARDIAC OUTPUT THE FICK METHOD: VO2 = ([O2]a - [O2]v) x Flow Spirometry (250 ml/min) VO2 [O2]a - [O2]v Flow = Pulmonary Artery Blood (15 ml%) Arterial Blood (20 ml%) CARDIAC OUTPUT PULMONARY BLOOD FLOW VENOUS RETURN PERIPHERAL BLOOD FLOW

  25. . VO2 [O2]a - [O2]v CARDIAC OUTPUT (Q) = 250 ml/min 20 ml% - 15 ml% = = 5 L/min . Q = HR x SV . . Q m2 body surface area Q HR CARDIAC INDEX = SV = 5 L/min 70 beats/min = 5 L/min 1.6 m2 = = 0.0714 L or 71.4 ml = 3.1 L/min/m2

  26. THE HEART AS A PUMP • REGULATION OF CARDIAC OUTPUT • Heart Rate via sympathetic & parasympathetic nerves • Stroke Volume • Frank-Starling “Law of the Heart” • Changes in Contractility • MYOCARDIAL CELLS (FIBERS) • Regulation of Contractility • Length-Tension and Volume-Pressure Curves • The Cardiac Function Curve

  27. Autoregulation (Frank-Starling “Law of the Heart”) CARDIAC OUTPUT = STROKE VOLUME x HEART RATE Contractility Sympathetic Nervous System Parasympathetic Nervous System

  28. CARDIAC MUSCLE - Functional Syncytium - Automaticity STRIATED MUSCLE SKELETAL MUSCLE - Motor Units - Stimulated by Motor Nerves

  29. STRUCTURE OF A MYOCARDIAL CELL Sarcolemma Mitochondria T-tubule SR Fibrils

  30. SARCOLEMMA 10% Mitochondria 20% 80% T-tubule Ca++ SR THICK MYOFILAMENT THIN MYOFILAMENT

  31. REGULATAION OF CONTRACTILITY • Recruitment of motor units • Increase frequency of firing of motor nerves • Calcium to trigger contraction

  32. INCREASING HEART RATE INCREASES CONTRACTILITY Ca++ Ca++ Normal Heart Rate Fast Heart Rate Ca++ Ca++ Ca++ Ca++

  33. SERIES ELASTIC ELEMENTS CONTRACTILE COMPONENT (ACTIVE TENSION) PARALLEL ELASTIC ELEMENTS (PASSIVE TENSION) TOTAL TENSION

  34. LENGTH-TENSION CURVE TOTAL TENSION ACTIVE TENSION TENSION PASSIVE TENSION OPTIMAL LENGTH (Lo) EQUILIBRIUM LENGTH RESTING LENGTH LENGTH LENGTH

  35. TENSION SARCOMERE LENGTH ()

  36. CARDIAC MUSCLE TOTAL TENSION ACTAIVE TENSION TENSION PASSIVE TENSION MUSCLE LENGTH

  37. HEART SYSTOLIC PRESSURE CURVE Isotonic (Ejection) Phase After-load Isovolumetric Phase PRESSURE Stroke Volume DIASTOLIC PRESSURE CURVE Pre-load End Systolic Volume End Diastolic Volume

  38. HEART INCREASED CONTRACTILITY SYSTOLIC PRESSURE CURVE Isotonic (Ejection) Phase After-load Isovolumetric Phase PRESSURE Stroke Volume DIASTOLIC PRESSURE CURVE Pre-load End Systolic Volume End Diastolic Volume

  39. HEART DECREASED CONTRACTILITY SYSTOLIC PRESSURE CURVE Isotonic (Ejection) Phase After-load Isovolumetric Phase PRESSURE Stroke Volume DIASTOLIC PRESSURE CURVE Pre-load End Systolic Volume End Diastolic Volume

  40. HEART INCREASED FILLING SYSTOLIC PRESSURE CURVE Isotonic (Ejection) Phase After-load Isovolumetric Phase PRESSURE Stroke Volume DIASTOLIC PRESSURE CURVE Pre-load End Systolic Volume End Diastolic Volume

  41. CARDIAC FUNCTION CURVE Cardiac Output = Stroke Volume x Heart Rate Constant If: STROKE VOLUME Then:  CO reflects SV DIASTOLIC FILLING Right Atrial Pressure (RAP) reflects Diastolic Filling

  42. CARDIAC FUNCTION CURVE THE FRANK- STARLING “LAW OF THE HEART” 15- 10- CARDIAC OUTPUT (L/min) Pressure 5- Volume -4 0 +4 +8 RAP mmHg

  43. CARDIAC FUNCTION CURVE THE FRANK- STARLING “LAW OF THE HEART” 15- Increased Contractility 10- CARDIAC OUTPUT (L/min) 5- -4 0 +4 +8 RAP mmHg

  44. CARDIAC FUNCTION CURVE THE FRANK- STARLING “LAW OF THE HEART” 15- Decreased Contractility 10- CARDIAC OUTPUT (L/min) 5- -4 0 +4 +8 RAP mmHg

  45. CARDIAC FUNCTION CURVE THE FRANK- STARLING “LAW OF THE HEART” 15- Increased Heart Rate 10- CARDIAC OUTPUT (L/min) 5- -4 0 +4 +8 RAP mmHg

  46. CARDIAC FUNCTION CURVE THE FRANK- STARLING “LAW OF THE HEART” 15- Decreased Heart Rate 10- CARDIAC OUTPUT (L/min) 5- -4 0 +4 +8 RAP mmHg

  47. P1 > P2 P1 FLOW P2 mm Hg P = FLOW x R P R FLOW = P FLOW R = L/min or ml/sec mm Hg ml/sec Peripheral Resistance Units (PRU)

  48. LAMINAR or STREAMLINE FLOW P1 P2 P1 > P2 -Cone Shaped Velocity Profile -Not Audible with a Stethoscope

  49. MEASURING BLOOD PRESSURE TURBULENT FLOW 1. Cuff pressure > systolic blood pressure--No sound. 2. The first sound is heard at peak systolic pressure. 3. Sounds are heard while cuff pressure < blood pressure. 4. Sound disappears when cuff pressure < diastolic pressure.

  50. RESISTANCES IN SERIES RT = RA + RC + RV RESISTANCES IN PARALLEL FlowT = Flow1 + Flow2 + Flow3 P RT P R1 P R2 P R3 = + + R1 PV PA 1 RT 1 R1 1 R2 1 R3 R2 = + + R3 1 RT = 1 R1 1 R2 1 R3 + +