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Chapter 14a

Chapter 14a. Cardiovascular Physiology. About this Chapter. Overview of the cardiovascular system Pressure, volume, flow, and resistance Cardiac muscle and the heart The heart as a pump. Overview: Cardiovascular System. Table 14-1. Overview: Cardiovascular System. Veins. Capillaries.

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Chapter 14a

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  1. Chapter 14a Cardiovascular Physiology

  2. About this Chapter • Overview of the cardiovascular system • Pressure, volume, flow, and resistance • Cardiac muscle and the heart • The heart as a pump

  3. Overview: Cardiovascular System Table 14-1

  4. Overview: Cardiovascular System Veins Capillaries Arteries Head andBrain Arms Pulmonaryveins Ascending arteries Lungs Superior vena cava Pulmonaryarteries Right atrium Aorta Left atrium Coronary arteries Abdominal aorta Left ventricle Right ventricle Heart Inferior vena cava Trunk Hepatic artery Hepatic portal vein Hepaticvein Digestivetract Liver Renalveins Renalarteries Ascending veins Descending arteries Venous valve Kidneys Pelvis andLegs Figure 14-1

  5. Pressure Gradient in Systemic Circulation • Blood flows down pressure gradients Figure 14-2

  6. Pressure Differences in Static and Flowing Fluids • The pressure that blood exerts on the walls of blood vessels generates blood pressure Figure 14-3a

  7. Pressure Differences in Static and Flowing Fluids • Pressure falls over distance as energy is lost due to friction Figure 14-3b

  8. Pressure Change • Pressure created by contracting muscles is transferred to blood • Driving pressure for systemic flow is created by the left ventricle • If blood vessels constrict, blood pressure increases • If blood vessels dilate, blood pressure decreases • Volume changes greatly affect blood pressure in CVS

  9. Fluid Flow through a Tube Depends on the Pressure Gradient • Flow  ∆P ★ Figure 14-4a

  10. Fluid Flow through a Tube Depends on the Pressure Gradient Figure 14-4b

  11. Fluid Flow through a Tube Depends on the Pressure Gradient Figure 14-4c

  12. As the Radius of a Tube Decreases, the Resistance to Flow Increases ★ Figure 14-5

  13. Flow Rate is Not the Same as Velocity of Flow • Flow (Q): volume that passes a given point • Velocity of flow (V): speed of flow • V = Q/A A= cross sectional area • Leaf in stream • Mean arterial pressure  cardiac output  peripheral resistance (varies by X-sec of arteries) Figure 14-6

  14. Structure of the Heart • The heart is composed mostly of myocardium STRUCTURE OF THE HEART Aorta Pulmonaryartery Superiorvena cava Auricle ofleft atrium Rightatrium Pericardium Coronaryarteryand vein Rightventricle Leftventricle Diaphragm (e) The heart is encased withina membranous fluid-filledsac, the pericardium. (f) The ventricles occupy the bulk ofthe heart. The arteries and veins allattach to the base of the heart. Figure 14-7e–f

  15. Anatomy: The Heart Table 14-2

  16. Structure of the Heart • The heart valves ensure one-way flow Pulmonarysemilunar valve Aorta Rightpulmonaryarteries Left pulmonaryarteries Superiorvena cava Left pulmonaryveins Right atrium Left atrium Cusp of the AV(bicuspid) valve Cusp of a right AV(tricuspid) valve Chordae tendineae Papillary muscles Left ventricle Right ventricle Inferiorvena cava Descendingaorta (g) One-way flow through the heartis ensured by two sets of valves. Figure 14-7g

  17. Heart Valves Figure 14-9a–b

  18. Heart Valves Figure 14-9c–d

  19. Anatomy: The Heart PLAY Interactive Physiology® Animation: Cardiovascular System: Anatomy Review: The Heart

  20. Cardiac Muscle (a) Intercalated disk(sectioned) Nucleus Intercalated disk Mitochondria Cardiac muscle cell Contractile fibers (b) Figure 14-10

  21. Action potential entersfrom adjacent cell. 9 1 10 Ca2+ 3 Na+ Ca2+ 2 K+ 1 ECF Voltage-gated Ca2+channels open. Ca2+enters cell. ATP NCX 2 ICF 3 Na+ Ca2+ RyR Ca2+ induces Ca2+ releasethrough ryanodinereceptor-channels (RyR). 3 2 3 Sarcoplasmic reticulum(SR) L-typeCa2+channel SR Local release causesCa2+ spark. Ca2+ 4 Ca2+ stores 4 ATP Summed Ca2+ sparkscreate a Ca2+ signal. 5 8 T-tubule Ca2+ sparks Ca2+ ions bind to troponinto initiate contraction. 6 5 Relaxation occurs whenCa2+ unbinds from troponin. Ca2+ Ca2+ Ca2+ signal 7 6 7 7 Actin Ca2+ is pumped backinto the sarcoplasmicreticulum for storage. 8 Ca2+ is exchanged withNa+ by the NCX antiporter. 9 Myosin Relaxation Contraction Na+ gradient is maintainedby the Na+-K+-ATPase. 10 Cardiac Muscle • Excitation-contraction coupling and relaxation in cardiac muscle Ca+2 • Autorhythmic cells – pacemakers set heart rate ~ 70 / min • Auto or self generate action potentials – stimulate neighboring cells to generate action potentials Figure 14-11

  22. Cardiac Muscle Contraction • Can be graded • Sarcomere length affects force of contraction • Action potentials vary according to cell type

  23. Myocardial Contractile Cells • Action potential of a cardiac contractile cell • Refractory period in cardiac muscle – long no tetanus PX = Permeability to ion X PNa 1 +20 2 PK and PCa 0 –20 Membrane potential (mV) 3 PK and PCa 0 –40 PNa –60 –80 4 4 –100 0 100 200 300 Time (msec) Phase Membrane channels 0 Na+ channels open 1 Na+ channels close 2 Ca2+ channels open; fast K+ channels close 3 Ca2+ channels close; slow K+ channels open 4 Resting potential Figure 14-13

  24. Long refractory period in cardiac muscle

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