Download The Cardiovascular System

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
Ventilation-Perfusion Relationships
Ventilation
O2 enters the lung
CO2 leaves the lung
P!(O2) = 100 mm
P!(CO2)= 40 mm
P!(O2) = 40 mm
P!(O2) = 100 mm
P!(CO2)= 45 mm
P!(CO2)= 40 mm
CO2 enters the lung
Respiratory Exchange Ratio
O2 leaves the lung
Perfusion
8.63 R*[CA(O2) - CV(O2)]Q = V P(CO2)
Increase V/Q
(Shunt) : Increase P(O2) / Decrease P(CO2) (hypocapnia)
Decrease V/Q (Ventilation Defect) : Decrease P(O2) / Increase P(CO2) (hypercapnia)
Blood (5 liters or 11 pints)
• plasma + RBC + WBC + platelets
(erythrocytes)
5x106/mm3
(leukocytes)
7000/mm3
(clotting)
2x105/mm3
• Plasma: H2O + electrolytes (ions/Ca) + proteins
• RBC: hematocrit = VRBC/Vtotal
• WBC: 50-70% Phagocytes 20-40% Lymphocytes
neutrophils (gobblers)
1-4% eosinophils
(eat paracites; allergy complex)
produce antibodies
<1% Basophils 2-4% Monocyte
(histamines)
(macrophages - BIG)
Blood
• Density: rblood = 1.04 gm/cm3 = 1.04x103 kg/m3
15
h (10-3 Pa*s)
• Viscosity:
10
5
0
0
25
50
75
Hematocrit (%)
DP = R * (DV/Dt)
R = 8phL/A2 !(tube)
100
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
O2
CO2
Blood Flow
100%
LUNGS
RIGHT HEART
100%
LEFT HEART
HEART MUSCLE
BRAIN
SKELTAL MUSCLE
BONE
3%
14%
15%
5%
GI SYSEM
21%
LIVER
6%
KIDNEY
SKIN
OTHER
22%
6%
8%
The Heart
Aorta
Pulmonary Artery
Pulmonary Veins
Right Heart
Inferior
vena cava
Aorta
Heart Chambers and Valves
Pulmonary
artery
Aorta
Vena cava
Left Atrium
Pulmonary Veins
4
Right Atrium
3
1
Right Ventricle
Valves
1. Tricuspid valve
2. Pulmonic valve
3. Mitral valve
4. Aortic valve
2
Left Ventricle
Myocardium
Cardiac Output
• Cardiac Output = Heart Rate x Stroke Volume
liters/min
5.8 l/m
beats/min x
= 72 b/m x
liters/beat
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)
Cardiac Output
r
Intraventricular
Pressure (mm Hg)
1. Tricuspid valve
2. Pulmonic valve
3. Mitral valve
4. Aortic valve
120
60
Ejection
AV opens
4
1 2
Diastolic filling
(P constant) Blood is “ incompressible”
P=g/4r
Left
g increases when
2r
venticle
cardiac muscles contract
r
3
Isovolumetric
Contraction
2r
P (g) increases 25x
Frank-Starling Law
systole ejection
AV opens
isovolumetric
relaxation
diastolic
filling
isovolumetric
contraction
mitral valve
opens
0
0
60
120 Ventricular Volume (ml)
increase
Stroke
Volume
Stroke Volume
Isovolumetric
relaxation
P decreases 50x
diastole volume
(filling pressure)
Cardiac Output Control
•
•
•
•
Cardiac Parasympathetic Nerve Activity:
Cardiac Sympathetic Nerve Activity:
Arterial Pressure:
Filling Pressure (Frank-Starling Law):
HR (-)
HR (+)/SV (+)
SV (-)
SV (+)
Cardiac Output: Work and Energy
Intraventricular
Pressure (mm Hg)
Area =∫ P dV = W = 1.2 J/Beat
Power = W x HR ~ 1 watt = 20 kcal/day
120
isovolumetric
relaxation
60
ejection
AV opens
isovolumetric
contraction
mitral valve
opens
0
0
60
120 Ventricular Volume (ml)
increase
Stroke
Volume
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.
Vascular System
Capillary Connects Artery to Vein
Aorta
Vein
Right Heart
Pulmonary
Artery
Left Heart
Pulmonary
Vein
Pulmonary Capillary Bed
O2
CO2
Alveolar Space
Pressure Drops
Q = DPA2/8phL
(Poiseuille equation)
Capillaries: Q= 50 pl/s
h (10-3 Pa*s)
DP = R * Q
R = 8phL/A2 !(tube)
15
10
5
0
0
25
50
75
100
Hematocrit (%)
Left Ventricle
120 mm Hg
Aorta
Arterioles
Pressure
Capillaries
Veins
Right Ventricle
Position
Blood Velocity
Q (m3/s) = v (m/s) * A (m2)
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
Cardiac Cycle
• Left Heart
– Diastole (lowest aortic presure): ventricle contracts
0-0.02 s
0- 0.1 s
0.1-0.25 s
...
aortic valve opens - HEART SOUND
aortic pressure increases to Systole
aortic valve closes as blood leaves ventricle
Heart Valves
An estimated 78,000 people get replacement heart valves in the United States each year,
according to the American Heart Association.
Electrocardiology
ra
ce
3
+t
+
Electrode
(1 of 3)
2
ce
- tra
-
- trace 1 +
Motion of dipole after impulse
Lead 2
“P wave”
Left Leg
A wave of - and + charge moves across the heart muscle and is measurable on the skin
Potential changes of 0.001 Volt arise