circulation v. veins regulation of arterial blood pressure
TRANSCRIPT
Circulation V.
Veins
Regulation of Arterial Blood Pressure
Veins.
• Blood flows from the capillaries into the venules, small veins, large veins and into the right atrium.
• Some exchange of molecules occurs between the venules and the interstitial fluid.
• Most of the blood is in the veins.
• Blood reservoir.
• The force driving the blood in the veins is the pressure difference between peripheral veins (5-10 torr) and the right atrium (0 torr).
• Veins are low resistance high capacitance (=compliance) vessels.
• Valves in veins allow flow in one direction.
Venous Valves
• Walls contain smooth muscle innervated by sympathetic nerves that release NE.
• NE causes venoconstriction.
• Skeletal muscle pump.• Respiratory pump.
Arterial Blood Pressure Regulation.
• Mean arterial blood pressure (MAP) has to be regulated to insure proper blood flow to tissues.
• High MAPtissue damage.• Low MAP poor tissue perfusion. • MAP = CO x TPR• TPR = total peripheral resistance
(sum of resistances of arterioles)
MAP = CO x TPR
• MAP = CO x TPR.• CO determines the rate at
which blood goes into the art. system.
• TPR determines the rate at which blood leaves the art. system.
• MAP depends on volume of blood in the art. system.
Baroreceptor Reflex.
Arterial Baroreceptors
• Pressure receptors (stretch receptors).
• When blood pressure goes up the receptors are stretched and fire APs.
Carotid Sinus and Aortic Arch Receptors.
Effects of Gravity.