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Cardiovascular Physiology

Cardiovascular Physiology. The circulatory system is the transport system of the body. The three basic components of the circulatory system Anatomy of the heart as a specialized organ pumping blood to the whole body Cardiac muscle with its specialized pacemaker and contractile cell

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Cardiovascular Physiology

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  1. Cardiovascular Physiology • The circulatory system is the transport system of the body. • The three basic components of the circulatory system • Anatomy of the heart as a specialized organ pumping blood to the whole body • Cardiac muscle with its specialized pacemaker and contractile cell • The origin and conduction of the cardiac impulse • The excitation –contraction coupling in the heart muscle

  2. Three basic components • The heart :serves as a pump imparting pressure to the blood. This establishes the pressure gradient needed for the blood to flow to the tissues. • The blood vessels : serves as a passage way through which blood is directed and distributed from the heart to all parts of the body and subsequently returned to the heart. - Arteries - Veins • The blood: serves as the transport medium. Hemoglobin ?

  3. A muscular organ • Pericardium • Pericardial Fluid

  4. Four chambers • Atria • Ventricles • Septum

  5. Heart Valves • Right and left atrioventricular (AV) valves The right side valves -tricuspid The left side valves – bicuspid (mitral) Chordae tendineae Papillary muscles • Right and left Semi lunar valves No valves between atria and the veins.

  6. Flow of Blood

  7. Overview of Circulation • Pulmonary circulation • Systemic circulation • Oxygenated • Deoxygenated Pelvis and Legs

  8. How Blood Flows? • Pressure gradient- - Highest in chambers of heart - Lowest in the vena cava • Loss of pressure- Friction between fluid and blood vessel walls IschemiaMyocardial infarction

  9. Changes in Pressure • Pressure decreases over distance Hydraulics- Study of fluid in motion • Compression raises pressure

  10. Velocity of Flow • Resistance opposes flow • Flow rate • Cross sectional area Velocity = Flow rate / cross–sectional area

  11. The cardiac Muscle • Most of the heart wall is composed of cardiac muscle or the myocardium consisting of bundles of cardiac muscle fibersarranged spirally around the circumference of the heart. • The individual cardiac muscle fibers form interconnecting branching fibers . The adjacent cells are joined end to end with specialized structures –Intercalated disks.

  12. Intercalated disks The intercalated disks have two types of membranous junctions: – • The desmosomes -provide mechanical support • The gap junctions -areas of low electrical resistance allowing action potential to spread from one cell to the other. No gap junctions between the atrial and ventricular contractile cells

  13. Cardiac Muscle Fibers

  14. Cardiac Muscle Fibers

  15. Myocardial cells • Myocardial cells are striated • Have sarcomeres • Much smaller than skeletal muscle fibers • Connected by gap junctions at intercalated discs • Lots of mitochondria. Why? • Lots of blood flow to myocardial cells

  16. More about myocardial cells • Large branching t-tubules • Sparse sarcoplasmic reticulum • Source of Ca++ is largely extra cellular

  17. Autorhythmic cells /Pace makers • Specialized myocardial cells which set the rate of the heart beat. • Ability to contract without any outside signal. • Smaller and have few contractile fibers • Initiate and conduct the action potential

  18. Autorhythmic cells /Pace makers • Don’t have a resting potential ,display pacemaker activity i.e. their membrane potential slowly depolarizes or drifts between action potentials until threshold is reached. At that time the membrane fires an action potential. • The most important changes in ion movement giving rise to pacemaker potential are the decreased outward K+ current coupled with a constant inward Na+and Ca++ current. MyogenicNeurogenic

  19. Where are Autorhythmic cells? • The sinoatrial node (SA node): a small specialized region in the right atrial wall near the opening of the superior vena cava • The AV node : a small bundle located at the base of the right atrium near the septum • The bundle of His :a tract of specialized cells originating at the AV node and enters the inter ventricular septum • The purkinje fibers: small terminal fibers that extend from the bundle of His and spread throughout the ventricular myocardium.

  20. Specialized Conduction System

  21. Conduction in the Heart • An action potential in an autorhythmic cell • Spreading of depolarization through gap junctions • Depolarization wave followed by a wave of contraction • Atria contract followed by the ventricles Internodal pathways connecting SA to AV node conduct faster than the contractile cells of the atrium Apex to base contraction of ventricles? AV node delay?

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