The Cardiovascular System

1. The Cardiovascular System

2. Physiology of Circulation

3. Compare and Contrast – Arteries & Veins

4. 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 heart

5. Veins - Characteristics • Thin tunica media (smooth muscle layer) • Larger lumen • Rely on other structures to help return blood to heart • Valves • Skeletal muscle • Pressure changes in thoracic cavity

6. Arterial Pulse • Pulse: the alternating expansion and recoil of artery as the left ventricle contracts • Usually equals pulse rate • Normal pulse rate: 70-76 bpm • Pressure points: pulse points compressed to stop blood flow

7. 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

8. You Decide: • Which was cut in the man – an artery or vein? How do you know? • http://www.youtube.com/watch?v=hsM0CwqGrBs

9. Measuring Blood Pressure • Systolic pressure: pressure in arteries at the peak of ventricular contraction • Diastolic pressure: pressure when ventricles relax • normal BP: 120 (systolic)/80 (diastolic)

10. 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

11. 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)