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Chapter 14a Cardiovascular Physiology. About this Chapter Overview of the cardiovascular system Pressure, volume, flow, and resistance Cardiac muscle.

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Presentation on theme: "Chapter 14a Cardiovascular Physiology. About this Chapter Overview of the cardiovascular system Pressure, volume, flow, and resistance Cardiac muscle."— Presentation transcript:

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 Figure 14-1 Ascending arteries Descending arteries Abdominal aorta Left atrium Left ventricle Heart Right ventricle Renal veins Renal arteries Hepatic vein Right atrium Coronary arteries Pulmonary veins Pulmonary arteries Superior vena cava Inferior vena cava Ascending veins Venous valve Arms Lungs Aorta Trunk Kidneys Pelvis and Legs Liver Digestive tract Hepatic artery Hepatic portal vein CapillariesArteriesVeins Head and Brain

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 Figure 14-7e–f Diaphragm (e) The heart is encased within a membranous fluid-filled sac, the pericardium. Pericardium STRUCTURE OF THE HEART (f) The ventricles occupy the bulk of the heart. The arteries and veins all attach to the base of the heart. Superior vena cava Right atrium Auricle of left atrium Aorta Pulmonary artery Right ventricle Left ventricle Coronary artery and vein

15 Anatomy: The Heart Table 14-2

16 Structure of the Heart The heart valves ensure one-way flow Figure 14-7g (g) One-way flow through the heart is ensured by two sets of valves. Right atriumLeft atrium Pulmonary semilunar valve Right pulmonary arteries Right ventricle Superior vena cava Left pulmonary arteries Aorta Left pulmonary veins Cusp of the AV (bicuspid) valve Cusp of a right AV (tricuspid) valve Chordae tendineae Inferior vena cava Papillary muscles Left ventricle Descending aorta

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 Figure (b) Contractile fibers Nucleus Mitochondria Cardiac muscle cell (a) Intercalated disk (sectioned) Intercalated disk

21 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 Ca 2+ ions bind to troponin to initiate contraction. Relaxation occurs when Ca 2+ unbinds from troponin. Na+ gradient is maintained by the Na + -K + -ATPase. Voltage-gated Ca 2+ channels open. Ca 2+ enters cell. Ca 2+ induces Ca 2+ release through ryanodine receptor-channels (RyR). Local release causes Ca 2+ spark. Ca 2+ is pumped back into the sarcoplasmic reticulum for storage. Ca 2+ is exchanged with Na + by the NCX antiporter. Action potential enters from adjacent cell. Summed Ca 2+ sparks create a Ca 2+ signal. ATP NCX 3 Na + 2 K + ATP Sarcoplasmic reticulum (SR) Myosin Actin Relaxation Ca 2+ Ca 2+ stores ECF ICF T-tubule L-type Ca 2+ channel Ca 2+ Ca 2+ sparks Ca 2+ signal Contraction Ca 2+ SR RyR

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 Figure Time (msec) P X = Permeability to ion X P K and P Ca P Na P K and P Ca +20 –20 –40 –60 –80 –100 PhaseMembrane channels Na + channels open Na + channels close Ca 2+ channels open; fast K + channels close Ca 2+ channels close; slow K + channels open Resting potential P Na Membrane potential (mV)

24 Long refractory period in cardiac muscle


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