Physiology of Circulation

Vital signs Arterial pulse Blood pressure Respiratory rate Pressure wave created by left ventricle after each heart beat Human average: 70-76 beats/ minute Blood pressure Pressure blood exerts against inner walls of blood vessels (allows blood to keep moving even between heart beats) Respiratory rate Breathing rate Body temperature

Arterial Pulse Body sites where pulse is most easily palpated

Blood Pressure Blood moves along a pressure gradient High  low Pressure of blood is highest in arteries and decreases as you move from the arteries to arterioles to capillaries to veins You can tell the difference in pressure of veins versus arteries, when you look at what happens when each are cut

Measuring Blood Pressure Two measurements Systolic pressure Pressure in arteries at the peak of ventricular contraction Diastolic pressure Pressure when the ventricles are relaxed Written: systolic pressure / diastolic pressure

Effects of Various Factors on Blood Pressure Cardiac output Amount of blood pumped out of left ventricle Determined by stroke volume and heart rate Peripheral resistance Friction encountered by blood as it flows through blood vessels Caused by: Narrowing/constriction of blood vessels Increased blood volume or viscosity (thickness)

Variation in Blood Pressure Average Blood Pressure: 110-140 / 75-80 Hypotension: Low blood pressure Systolic below 100 Hypertension: High blood pressure Sustained elevated blood pressure of 140/90 or higher

Measuring Blood Pressure