Transcript 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 Arteries Head and Brain Arms Lungs Superior vena cava Pulmonary arteries Right atrium Pulmonary veins Ascending arteries Aorta Left atrium Coronary arteries Left ventricle Abdominal aorta Right ventricle Heart Inferior vena cava Trunk Hepatic artery Hepatic portal vein Hepatic vein Digestive tract Liver Ascending veins Renal veins Renal arteries Descending arteries Venous valve Kidneys Pelvis and Legs Figure 14-1 Pressure Gradient in Systemic Circulation • Blood flows down pressure gradients Figure 14-2 Pressure Differences in Static and Flowing Fluids • The pressure that blood exerts on the walls of blood vessels generates blood pressure Figure 14-3a Pressure Differences in Static and Flowing Fluids • Pressure falls over distance as energy is lost due to friction Figure 14-3b 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 Fluid Flow through a Tube Depends on the Pressure Gradient • Flow ∆P ★ Figure 14-4a Fluid Flow through a Tube Depends on the Pressure Gradient Figure 14-4b Fluid Flow through a Tube Depends on the Pressure Gradient Figure 14-4c As the Radius of a Tube Decreases, the Resistance to Flow Increases ★ Figure 14-5 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 Structure of the Heart • The heart is composed mostly of myocardium STRUCTURE OF THE HEART Aorta Superior vena cava Pericardium Right atrium Right ventricle Pulmonary artery Auricle of left atrium Coronary artery and vein Left ventricle Diaphragm (e) The heart is encased within a membranous fluid-filled sac, the pericardium. (f) The ventricles occupy the bulk of the heart. The arteries and veins all attach to the base of the heart. Figure 14-7e–f Anatomy: The Heart Table 14-2 Structure of the Heart • The heart valves ensure one-way flow Aorta Pulmonary semilunar valve Right pulmonary arteries Superior vena cava Left pulmonary arteries Left pulmonary veins Left atrium Right atrium Cusp of the AV (bicuspid) valve Cusp of a right AV (tricuspid) valve Chordae tendineae Papillary muscles Left ventricle Right ventricle Inferior vena cava Descending aorta (g) One-way flow through the heart is ensured by two sets of valves. Figure 14-7g Heart Valves Figure 14-9a–b Heart Valves Figure 14-9c–d Anatomy: The Heart PLAY Interactive Physiology® Animation: Cardiovascular System: Anatomy Review: The Heart Cardiac Muscle (a) Intercalated disk (sectioned) Nucleus Intercalated disk Mitochondria Cardiac muscle cell Contractile fibers (b) Figure 14-10 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 10 Ca2+ 1 ECF 2 K+ ATP ICF 9 3 Na+ Ca2+ 1 Action potential enters from adjacent cell. NCX 3 Na+ RyR 2 Ca2+ 2+ 2+ 3 Ca induces Ca release through ryanodine receptor-channels (RyR). 2 3 L-type Ca2+ channel SR Ca2+ 4 Sarcoplasmic reticulum (SR) release causes 4 Local Ca2+ spark. Ca2+ stores ATP Ca2+ sparks T-tubule Voltage-gated Ca2+ channels open. Ca2+ enters cell. 2+ 5 Summed Ca sparks create a Ca2+ signal. 8 2+ 6 Ca ions bind to troponin to initiate contraction. 5 Ca2+ signal 6 Contraction Ca2+ 7 Relaxation occurs when Ca2+ unbinds from troponin. Ca2+ 7 7 Relaxation Actin Myosin 2+ 8 Ca is pumped back into the sarcoplasmic reticulum for storage. 2+ 9 Ca is exchanged with Na+ by the NCX antiporter. 10 Na+ gradient is maintained by the Na+-K+-ATPase. Figure 14-11 Cardiac Muscle Contraction • Can be graded • Sarcomere length affects force of contraction • Action potentials vary according to cell type Myocardial Contractile Cells • Action potential of a cardiac contractile cell • Refractory period in cardiac muscle – long no tetanus Membrane potential (mV) 1 +20 PX = Permeability to ion X PNa 2 PK and PCa 0 –20 3 –40 0 –60 PNa –80 4 PK and PCa 4 –100 0 Phase 100 200 Time (msec) 300 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 Long refractory period in cardiac muscle