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# Heartbeat **Pulse:** The alternate expansion and contraction of arteries (72 bpm) **Blood pressure:** The force exerted by the blood against the walls of blood vessels (120/80 mm) ## Arteries vs. Veins | Feature | Arteries | Veins | |---|---|---| | Direction | Away from heart | Towards heart |...

# Heartbeat **Pulse:** The alternate expansion and contraction of arteries (72 bpm) **Blood pressure:** The force exerted by the blood against the walls of blood vessels (120/80 mm) ## Arteries vs. Veins | Feature | Arteries | Veins | |---|---|---| | Direction | Away from heart | Towards heart | | Pressure | High pressure | Low pressure | | Wall Thickness | Thick walls | Thin walls | | Lumen Size | Small lumen | Large lumen | | Valves | NO VALVES | Valves (prevent backflow) | ## Blood Supply to Heart **Coronary arteries and veins** ## Stages of Heartbeat **Diastole:** Heart is relaxed **Systole:** Heart is contracting **Diastole:** * All atria and ventricles are relaxed * Blood enters both atria * All values are closed **→Blood from atria to ventricles** * SA node causes both atria to contract * Bicuspid & tricuspid valves open to force blood into both ventricles **Systole** * Semi lunar valves are closed * Blood leaving heart (away) * The atria relax (Diastole) * AV node causes both ventricles to contract (systole) * Blood is forced out through semi lunar values (systole) **When all blood has left the ventricles, semi-lunar valves close** **→END OF CYCLE←**