7 Cardiovascular System – Blood Flow / Pressure (7/6) -- Workbook for BIOL2010U Human Physiology

7 Cardiovascular System – Blood Flow / Pressure Objectives - Arteries and Arterial Blood Pressure - Overview of Arterioles and Resistance to Flow - Factors Affecting Arterial Blood Pressure - Veins Interactive Activities Critical Thinking Questions Learning Summary Pressure Reservoirs: ensures smooth flow of blood even when in diastole (when the heart stops). Elastic fibers: act as springs that store elastic force and passively recoil. Compliance: a measure of how the pressure of a vessel will change with a change in volume. Low compliance (arteries); High compliance (veins). Arterial Blood Pressure = pressure in the aorta Systolic blood pressure – Max pressure Diastolic blood pressure – Min pressure Mean arterial pressure – Average pressure Arterioles: resistance levels Part of microcirculation - Connect arteries to capillaries or metarterioles - Connect rings of smooth muscle to regulate radius, and therefore, resistance - Best site where resistance to flow can be regulated Arterioles and resistance to blood flow TBR = combined resistance of all blood vessels with the circuit Largest pressure drop in vascular occurs along arterioles Changes in arteriole radius - Arteriole tone - Vasoconstriction - Vasodilation Intrinsic Control of Arteriole Smooth Muscle happens via: - Changes in metabolic activity (active hyperemia) - Changes in blood flow (reactive hyperemia) - Stretch of smooth muscles in arterioles (increases myogenic response) - Local chemical messengers - Capillaries and Venules Microcirculation: Arterioles, Metarterioles, Precapillary sphincters Transport mechanisms: Simple diffusion, Mediated transport, Transcytosis Bulk flow across capillary walls: Move from blood to interstitial fluid and interstitial fluid to blood (Net filtration pressure= filtration pressure – absorption pressure). Veins = volume reservoir and have high compliance Factors influence pressure and return Skeletal muscle pump = one way, absent from central veins, contraction/relaxation Respiratory pump = Inspiration and Exhalation Blood Volume = increased blood volume–increased pressure vice-versa Venomotor tone = 2 effects: constriction raises pressure–blood moves to heart, increase tension reduces compliance–raises pressure–increases stroke volume