Cardiovascular Physiology Chapter 14a Cardiovascular Physiology

Overview of the cardiovascular system 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 Pulmonary veins Ascending arteries Superior vena cava Pulmonary arteries Right atrium Aorta Left atrium Coronary arteries Left ventricle Abdominal aorta Right ventricle Heart Inferior vena cava Trunk Hepatic artery Hepatic vein Hepatic portal vein Liver Digestive tract Renal veins Renal arteries Ascending veins 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 created by contracting muscles is transferred to blood 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

The heart is composed mostly of myocardium Structure of the Heart The heart is composed mostly of myocardium STRUCTURE OF THE HEART Aorta Pulmonary artery Superior vena cava Auricle of left atrium Right atrium Pericardium Coronary artery and vein Right ventricle 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

Pulmonary semilunar valve Structure of the Heart The heart valves ensure one-way flow Aorta Pulmonary semilunar valve Right pulmonary arteries Left pulmonary arteries Superior vena cava Left pulmonary veins 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 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 Mitochondria Cardiac muscle cell Contractile fibers (b) Figure 14-10

Sarcoplasmic reticulum (SR) 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 1 2 3 4 5 6 7 8 9 10 Ca2+ ions bind to troponin to initiate contraction. Relaxation occurs when Ca2+ unbinds from troponin. Na+ gradient is maintained by the Na+-K+-ATPase. Voltage-gated Ca2+ channels open. Ca2+ enters cell. Ca2+ induces Ca2+ release through ryanodine receptor-channels (RyR). Local release causes Ca2+ spark. Ca2+ is pumped back into the sarcoplasmic reticulum for storage. Ca2+ is exchanged with Na+ by the NCX antiporter. Action potential enters from adjacent cell. Summed Ca2+ sparks create a Ca2+ signal. ATP NCX 3 Na+ 2 K+ Sarcoplasmic reticulum (SR) Myosin Actin Relaxation Ca2+ Ca2+ stores ECF ICF T-tubule L-type Ca2+ channel Ca2+ sparks Ca2+ signal Contraction SR RyR 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 PX = Permeability to ion X 1 PNa +20 2 PK and PCa –20 Membrane potential (mV) –40 3 PK and PCa –60 PNa –80 4 4 –100 100 200 300 Time (msec) Phase Membrane channels 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