Lecture 13: The Cardiovascular System ref: Cardiovascular Physiology, D. Mohrman and L. Heller, 4th ed. McGraw-Hill (1997)

Transcription

1 Lecture 13: The Cardiovascular System ref: Cardiovascular Physiology, D. Mohrman and L. Heller, 4th ed. McGraw-Hill (1997) Blood Heart Blood Vessels Arteries - capillaries - Veins

2 Ventilation-Perfusion Relationships O 2 enters the lung Ventilation CO 2 leaves the lung P (O 2 ) = 40 mm P (CO 2 )= 45 mm P (O 2 ) = 100 mm P (CO 2 )= 40 mm P (O 2 ) = 100 mm P (CO 2 )= 40 mm CO 2 enters the lung Respiratory Exchange Ratio Perfusion O 2 leaves the lung 8.63 R*[C A (O 2 ) - C V (O 2 )]Q = V P(CO 2 ) Increase V/Q (Shunt) : Increase P(O 2 ) / Decrease P(CO 2 ) (hypocapnia) Decrease V/Q (Ventilation Defect) : Decrease P(O 2 ) / Increase P(CO 2 ) (hypercapnia)

3 Blood (5 liters or 11 pints) plasma + RBC + WBC + platelets (erythrocytes) (leukocytes) (clotting) 5x10 6 /mm /mm 3 2x10 5 /mm 3 Plasma: H 2 O + electrolytes (ions/ca) + proteins RBC: hematocrit = V RBC /V total WBC: 50-70% Phagocytes 20-40% Lymphocytes neutrophils (gobblers) produce antibodies 1-4% eosinophils <1% Basophils 2-4% Monocyte (eat paracites; allergy complex) (histamines) (macrophages - BIG)

4 Blood Density: r blood = 1.04 gm/cm 3 = 1.04x10 3 kg/m 3 Viscosity: h (10-3 Pa*s) Hematocrit (%) DP = R * (DV/Dt) R = 8phL/A 2 (tube)

5 Blood 80 % systemic circulation 15% arterial 10% capillaries 75% venous Vena Cava Aorta Left Heart 20% pulmonary circulation 46% arterial 7% capillary 46% venous Pulmonary Artery Pulmonary Vein Pulmonary Capillary Bed O 2 CO 2

6 Blood Flow 100% LUNGS 100% RIGHT HEART LEFT HEART HEART MUSCLE BRAIN SKELTAL MUSCLE BONE GI SYSEM LIVER KIDNEY SKIN OTHER 3% 14% 15% 5% 21% 6% 22% 6% 8%

7 The Heart Aorta Pulmonary Artery Pulmonary Veins Right Heart Inferior vena cava Aorta

8 Heart Chambers and Valves Pulmonary artery Vena cava Aorta Left Atrium Right Atrium 4 3 Pulmonary Veins Right Ventricle 1 2 Left Ventricle Valves 1. Tricuspid valve 2. Pulmonic valve 3. Mitral valve 4. Aortic valve Myocardium

9 Cardiac Output Cardiac Output = Heart Rate x Stroke Volume liters/min beats/min x liters/beat 5.8 l/m = 72 b/m x 80 ml/b Stroke Volume Control Ventricular Pressure = Force/Area Muscles provide SURFACE TENSION (T = Force per unit length) P=T/r (cylinder) P=T/2r (sphere)

10 Cardiac Output 1. Tricuspid valve 2. Pulmonic valve 3. Mitral valve 4. Aortic valve Intraventricular Pressure (mm Hg) isovolumetric relaxation Isovolumetric relaxation P decreases 50x r Ejection AV opens ejection diastolic mitral valve filling opens increase 3 systole Stroke Volume r Left venticle AV opens 2r isovolumetric contraction Diastolic filling (P constant) 2r Ventricular Volume (ml) Isovolumetric Contraction P (g) increases 25x Frank-Starling Law Stroke Volume Blood is incompressible P=g/4r g increases when cardiac muscles contract diastole volume (filling pressure)

11 Cardiac Output Control Cardiac Parasympathetic Nerve Activity: HR (-) Cardiac Sympathetic Nerve Activity: HR (+)/SV (+) Arterial Pressure: SV (-) Filling Pressure (Frank-Starling Law): SV (+)

12 Cardiac Output: Work and Energy Area = P dv = W = 1.2 J/Beat Power = W x HR ~ 1 watt = 20 kcal/day Intraventricular Pressure (mm Hg) isovolumetric relaxation ejection mitral valve opens increase Stroke Volume AV opens isovolumetric contraction Ventricular Volume (ml)

13 Heart Muscle and Control Striated (like skeltal muscle) Autorhythmic (spontaneously contract) Individual cells of cardiac muscle isolated in a saline solution beat spontaneously at random rates. Sinoatrial node "pacemaker beats faster to control heart rhythm. The primary cardiovascular control center is located in the medulla oblongata of the brain The heart is innervated by sympathetic and parasympathetic nerve fibers. Temperature, ion concentration, and hormones affect heart rate.

14 Vascular System Capillary Connects Artery to Vein Vein Aorta Right Heart Left Heart Pulmonary Artery Pulmonary Vein Pulmonary Capillary Bed O 2 CO 2 Alveolar Space

15 Pressure Drops DP = R * Q R = 8phL/A 2 (tube) 120 mm Hg Pressure Q = DPA 2 /8phL (Poiseuille equation) Capillaries: Q= 50 pl/s Aorta Left Ventricle Arterioles Capillaries Veins h (10-3 Pa*s) Hematocrit (%) Right Ventricle Position

16 Blood Velocity Q (m 3 /s) = v (m/s) * A (m 2 ) DP=8phLv/A Capillary Blood Flow: v =Q/A ~1 mm/s Laminar vs Turbulent Flow Reynolds Number: R = rvr/h (for tube radius r) Laminar Flow: v Turbulent Flow: R > 1000 for blood: Aorta during systole

17 Left Heart Cardiac Cycle Diastole (lowest aortic presure): ventricle contracts s aortic valve opens - HEART SOUND s aortic pressure increases to Systole s aortic valve closes as blood leaves ventricle...

18 Heart Valves An estimated 78,000 people get replacement heart valves in the United States each year, according to the American Heart Association.

19 Electrocardiology Electrode (1 of 3) - trace trace trace 3 - Left Leg Motion of dipole after impulse Lead 2 P wave A wave of - and + charge moves across the heart muscle and is measurable on the skin Potential changes of Volt arise