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Understanding Cardiovascular Physiology: Heart Structure, Circulation, and Function

Explore the intricacies of cardiovascular physiology with a focus on heart structure, circulation, and function. Learn about mechanisms of cardiac contraction, blood flow dynamics, and regulation of heart rate. This chapter covers the anatomy and histology of the heart, the cardiovascular system overview, and more.

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Understanding Cardiovascular Physiology: Heart Structure, Circulation, and Function

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  1. Chapter 14 Cardiovascular Physiology

  2. About this Chapter • Blood flow pumping & distribution • Anatomy and histology of the heart • Mechanism of cardiac contraction • Heart beat sequence–how the pump works • Regulators of heart beat and volume pumped

  3. The Heart

  4. The Heart

  5. Normal and Abnormal Chest X-Rays

  6. Overview of the Cardiosvascular System • Heart and Blood vessels • Products transported to sustain all cells Table 14-1: Transport in the Cardiovascular System

  7. Circulation Reviewed • Heart – "four chambered" • Right atrium & ventricle • Pulmonary circuit • Left atrium & ventricle • Systemic circuit • Blood Vessels – "closed circulation" • Arteries –from heart • Capillaries– cell exchange • Veins – to heart

  8. Circulation Reviewed Figure 14-1: Overview of circulatory system anatomy

  9. Blood Flow: Pressure Changes • Flows down a pressure gradient • Highest at the heart (driving P), decreases over distance • Hydrostatic (really hydraulic) pressure in vessels • Decreases 90% from aorta to vena cava

  10. Blood Flow: Pressure Changes Figure 14-2 : Pressure gradient in the blood vessels

  11. Some Physic of Fluid Movement: Blood Flow • Flow rate: (L/min) • Flow velocity= rate/C-S area of vessel • Resistance slows flow • Vessel diameter • Blood viscosity • Tube length Figure 14-4 c: Pressure differences of static and flowing fluid

  12. Some Physic of Fluid Movement: Blood Flow Figure 14-6: Flow rate versus velocity of flow

  13. Heart Structure • Pericardium • Chambers • Coronary vessels • Valves-(one-way-flow) • Myocardium Figure 14-7 g: ANATOMY SUMMARY: The Heart

  14. Cardiac Muscle Cells: • Autorhythmic • Myocardial • Intercalated discs • Desmosomes • Gap Junctions • Fast signals • Cell to cell • Many mitochondria • Large T tubes Figure 14-10: Cardiac muscle

  15. Mechanism of Cardiac Muscle Excitation, Contraction & Relaxation Figure 14-11: Excitation-contraction coupling and relaxation in cardiac muscle

  16. Modulation of Contraction • Graded Contraction: proportional to crossbridges formed • More [Ca++]: crossbridges, more force & speed • Autonomic n & epinephrine modulation

  17. Modulation of Contraction Figure 14-12: Modulation of cardiac contraction by catecholamines

  18. More Characteristics of Cardiac Muscle Contraction • Stretch-length relationship •  stretch,  Ca++ entering •  contraction force • Long action potential • Long refractory period • No summation • No tetanus

  19. More Characteristics of Cardiac Muscle Contraction Figure 14-13: Length-tension relationships in skeletal and cardiac muscle

  20. More Characteristics of Cardiac Muscle Contraction Figure 14-15c: Refractory periods and summation in skeletal and cardiac muscle

  21. Autorhythmic Cells: Initiation of Signals • Pacemaker membrane potential • I-f channels Na+ influx • Ca++ channels – influx, to AP • Slow K+ open – repolarization

  22. Autorhythmic Cells: Initiation of Signals Figure 14-16: Action potentials in cardiac autorhythmic cells

  23. Sympathetic and Parasympathetic • Sympathetic – speeds heart rate by  Ca++ & I-f channel flow • Parasympathetic – slows rate by  K+ efflux &  Ca++ influx Figure 14-17: Modulation of heart rate by the nervous system

  24. Coordinating the Pump: Electrical Signal Flow • AP from autorhythmic cells in sinoatrial node (SA) • Spreads via gap junctions down internodal pathways and across atrial myocardial cells (atrial contraction starts) • Pause – atrioventricular (AV) node delay • AV node to bundles of His, branches & Purkinje fibers • Right and left ventricular contraction from apex upward

  25. Coordinating the Pump: Electrical Signal Flow Figure 14-18: Electrical conduction in myocardial cells

  26. Coordinating the Pump: Electrical Signal Flow Figure 14-19a: Electrical conduction in the heart

  27. Electrocardiogram (ECG):Electrical Activity of the Heart • Einthoven's triangle • P-Wave – atria • QRS- wave – ventricles • T-wave – repolarization Figure 14-20: Einthoven’s triangle

  28. Electrocardiogram (ECG):Electrical Activity of the Heart Figure 14-21: The electrocardiogram

  29. 3. Ventricular repolarization 2. Ventriculardepolarization 1. Atrial depolarization Electrocardiography (ECG) • Measures galvanically the electric activity of the heart • Well known and traditional, first measurements byAugustus Waller using capillary electrometer (year 1887) • Very widely used method in clinical environment • Very high diagnostic value

  30. 12-Lead ECG measurement • Most widely used ECG measurement setup in clinical environment • Signal is measured non-invasively with 9 electrodes • Lots of measurement data and international reference databases • Well-known measurement and diagnosis practices • This particular method was adopted due to historical reasons, now it is already rather obsolete Goldberger augmented leads: VR, VL & VF Einthoven leads: I, II & III Precordial leads: V1-V6

  31. ECG Information Gained • (Non-invasive) • Heart Rate • Signal conduction • Heart tissue • Conditions Figure 14-24: Normal and abnormal electrocardiograms

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