KNES 260 Lecture Notes - Lecture 9: Ultimate Tensile Strength, Vascular Resistance, Metarteriole
27 Feb 2017
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Blood Flow
● Blood flows from high to low pressure
●
○ Directly proportional to pressure gradient
○ Inversely proportional to vascular resistance
■ Depends on blood viscosity, vessel length, and vessel radius (most
important one)
● Driving pressure for the flow is created by the left ventricle
Structure of Blood Vessels
● 3 main layers are the connective tissue, smooth muscle, and endothelium
Arteries
● Have a high flow rate and pressure because of a large radius and low resistance
● Act as a “pressure reservoir” when the heart is relaxing
● Contain collagen and elastin fibers to help with tensile strength and stretch/recoil of the
walls
● Have a pulsatile flow, meaning that the pressure is different in systole and diastole
● Buildup of cholesterol in arteries is called atherosclerosis and increases blood pressure
Arterioles
● Major resistance vessels with adjustable radius
○ Adjustments serve to change distribution of cardiac output to meet the body's
needs
○ Regulate arterial blood pressure
● vasodilation/constriction can be triggered by several different local and central factors
○ Changes is O2 or CO2 levels
○ Histamine release
○ Endothelial factors (things released from endothelial cells)
○ Temperature changes
● There is also an extrinsic control through the sympathetic system and hormones
○ Alpha 1 receptors cause vasoconstriction when activated by norepinephrine
○ Alpha 2 receptors cause vasodilation when they are activated by epinephrine
(mostly in the heart and skeletal muscle)
Capillaries
● Precapillary sphincter restricts flow through the capillary beds when it isn’t needed
○ If closed it only allows flow through the metarteriole
● 3 main types
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Document Summary
Blood flows from high to low pressure. Depends on blood viscosity, vessel length, and vessel radius (most. Driving pressure for the flow is created by the left ventricle important one) 3 main layers are the connective tissue, smooth muscle, and endothelium. Have a high flow rate and pressure because of a large radius and low resistance. Act as a pressure reservoir when the heart is relaxing. Contain collagen and elastin fibers to help with tensile strength and stretch/recoil of the walls. Have a pulsatile flow, meaning that the pressure is different in systole and diastole. Buildup of cholesterol in arteries is called atherosclerosis and increases blood pressure. Adjustments serve to change distribution of cardiac output to meet the body"s needs. Vasodilation/constriction can be triggered by several different local and central factors. Endothelial factors (things released from endothelial cells) There is also an extrinsic control through the sympathetic system and hormones. Alpha 1 receptors cause vasoconstriction when activated by norepinephrine.
