4 Arteries - Characteristics Thicker tunica media – smooth muscle layerSmaller lumenElastic – stretch and recoil as blood is pumped throughHigh pressureCarry blood away from heart
5 Veins - Characteristics Thin tunica media (smooth muscle layer)Larger lumenRely on other structures to help return blood to heartValvesSkeletal musclePressure changes in thoracic cavity
6 Arterial PulsePulse: the alternating expansion and recoil of artery as the left ventricle contractsUsually equals pulse rateNormal pulse rate: bpmPressure points: pulse points compressed to stop blood flow
7 Blood PressurePressure blood exerts against the inner walls of the blood vesselsBlood flows from aorta arteries arterioles capillaries venules veins vena cavaPressure is strongest at the aorta, and zero at the vena cava
8 You Decide:Which was cut in the man – an artery or vein? How do you know?
9 Measuring Blood Pressure Systolic pressure: pressure in arteries at the peak of ventricular contractionDiastolic pressure: pressure when ventricles relaxnormal BP: 120 (systolic)/80 (diastolic)
10 Factors affecting blood pressure Peripheral resistanceFriction encountered as blood flows through vesselsAge, weight, time of day, exercise, body position, emotional state, drugsNeural factorsSympathetic system causes vasoconstriction of vessels which increases blood pressureRenal factors (kidneys)Alter blood volumeAs BP increases above normal, kidneys excrete more water into urine
11 Factors Continued Temperature Chemicals Diet Cold causes vasoconstriction, heat is a vasodilatorChemicalsNicotine causes vasoconstriction (increases bp), alcohol causes vasodilation (decreases bp)DietLow salt, saturated fats and cholesterol help prevent hypertension (high bp)