Outline-3, BIO 3360, Circulation V – Veins and Regulation of Arterial Blood Pressure

I. Veins carry blood towards the heart and contain most of the body’s blood

A. Veins have low driving pressure

B. Veins are low resistance, and are high capacitance (easily expand due to thin walls) or compliance vessels

C. Veins have one way valves

D. Blood moves through veins by pressure differences (venoconstriction can occur), skeletal muscle pump and respiratory pump

II. Arterial Blood Pressure Regulation

A. Mean Arterial Pressure = Cardiac Output x Total Peripheral Resistance

B. CO represents rate of blood going into arterial system and TPR represents the rate of blood going out of the arterial system from the arterioles

C. MAP depends on the volume of blood in the arterial system.  Increased volume of blood results in increased pressure.  For example, Antidiuretic Hormone (ADH) is released when you are dehydrated, because is keeps water in the bloodstream and prevents you from urinating out excessive water.

D. Baroreceptor reflex –increased pressure results in decreased heart rate and vasodilation to bring down high MAP

Video of baroreceptors

1. Baroreceptors are stretch receptors –when blood pressure increases, the receptors are stretched and fire action potentials

2. Baroreceptors are located in the Carotid Sinus and Aortic Arch

3. Gravity leads to decreased pressure to these baroreceptors and adjustments are made to ensure blood pressure/flow to the brain