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The Cardiovascular System
Physiology of Circulation
Compare and Contrast – Arteries & Veins
Arteries - Characteristics
• Thicker tunica media –
smooth muscle layer
• Smaller lumen
• Elastic – stretch and
recoil as blood is
pumped through
• High pressure
• Carry blood away from
Veins - Characteristics
• Thin tunica media
(smooth muscle layer)
• Larger lumen
• Rely on other structures
to help return blood to
– Valves
– Skeletal muscle
– Pressure changes in
thoracic cavity
Arterial Pulse
• Pulse: the alternating
expansion and recoil of
artery as the left
ventricle contracts
• Usually equals pulse
– Normal pulse rate: 7076 bpm
• Pressure points: pulse
points compressed to
stop blood flow
Blood Pressure
• Pressure blood exerts against the inner walls
of the blood vessels
• Blood flows from aorta  arteries arterioles
 capillaries  venules  veins  vena cava
– Pressure is strongest at the aorta, and zero at the
vena cava
You Decide:
• Which was cut in the man – an artery or
vein? How do you know?
Measuring Blood Pressure
• Systolic pressure:
pressure in arteries at
the peak of ventricular
• Diastolic pressure:
pressure when
ventricles relax
• normal BP: 120
(systolic)/80 (diastolic)
Factors affecting blood pressure
• Peripheral resistance
– Friction encountered as blood flows through vessels
– Age, weight, time of day, exercise, body position,
emotional state, drugs
• Neural factors
– Sympathetic system causes vasoconstriction of vessels
which increases blood pressure
• Renal factors (kidneys)
– Alter blood volume
– As BP increases above normal, kidneys excrete more
water into urine
Factors Continued
• Temperature
– Cold causes vasoconstriction, heat is a vasodilator
• Chemicals
– Nicotine causes vasoconstriction (increases bp),
alcohol causes vasodilation (decreases bp)
• Diet
– Low salt, saturated fats and cholesterol help
prevent hypertension (high bp)