Transcript Document

Cardiovascular System
Blood Vessels
Arteries
• Carry blood away from the heart
• Lumen
• Wall
– Tunica interna
– Tunica media
– Tunica externa
• Pulse
Arterioles
• Tiny arteries
• Primary resistance vessel
Capillaries
• Thin wall, one cell layer
• Diffusion
Venules
• Tiny veins
Veins
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Carry blood towards the heart
Low pressures
Valves
Skeletal muscle
Breathing
Sinuses
Blood reservoirs
• Veins and sinuses
Blood velocity
• Inversely proportional to total cross
sectional area of vessel
• Slowest in capillaries
Blood flow
• Flow = Pressure/Resistance
Pressure
• Force that drives blood through the vessels
due to pumping of heart
• Highest in aorta
• Lowest in vena cava
• Pulse
Resistance
• Blood viscosity
• Blood vessel length
• Vessel radius
– Resistance = 1/radius4
– Arterioles
Relationships
• F = P/R
• CO = P/R
• CO = Mean aortic pressure/total peripheral
resistance
• CO = Mean arterial pressure/total peripheral
resistance
• Mean arterial pressure = CO x TPR
Arterial Pressure
• Neural controls
– Vasomotor fibers
• Sympathetic efferent
• Vasodilator
• Vasoconstrictor
Arterial Pressure
• Neural controls
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Vasomotor Center
Cardiac Center
Baroreceptors in aortic arch and carotid sinus
Chemoreceptors in aortic and carotid bodies
for oxygen, carbon dioxide, hydrogen
Baroreceptors
Chemoreceptors
Arterial Pressure
• Chemicals & Hormones
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Angiotensin
Epinephrine
ADH (Vasopressin)
Blood volume
Epinephrine
Arterial Pressure
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Measurement
120/80 mmHg
Systolic pressure
Diastolic pressure
Venous Return
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Low pressures
Related to peripheral venous pressure
Skeletal muscles
Valves
Breathing (thoracoabdominal pump)
Arterial Pressure and Gravity
• Gravity
– Pressure increases inferiorly
– Increased capillary filtration to decrease blood
volume
– Baroreceptors
– Movement of skeletal muscle
Exercise and CV system
• Skeletal muscle vasodilation
– CNS sympathetic vasodilator fibers
– Low O2 levels
– Increased local vasodilator chemicals
Exercise
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Visceral vasoconstriction
Increased sympathetic stimulation to heart
Increased venous return
HR, SV, CO increase
Mean arterial pressure increases
Pulmonary Circuit
Systemic Circuit
• Aorta to Vena Cava
Fetal Circulation
• Placenta
• Umbilical cord
• Lung and liver bypass
Hypertension
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Causes:
Adrenal tumor
Kidney Disease
Volume loading
90% unknown
Consequences
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Heart – enlarged
Angina
Aneurysm
Sclerosis
Rupture of vessel
Kidney disease
Treatment
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Lose weight, exercise
Decrease salt, diuretics
Stop smoking, alcohol, caffeine
Biofeedback
Vasodilator drugs, e.g. isoproteronol