Blood Pressure and its regulation Flashcards
Define Total Peripheral Resistance (TPR)
The combined resistance of all the blood vessels in the systemic circulation.
What is the pressure gradient and resistance in systemic circulation? (2 related formulas)
Flow(from the heart) = ^P/RCO = MAP/TPR (2nd law)CO = Hr /SV
Name the 5 types of vessels
ArteriesArteriolesCapillariesVenulesVeins
Describe the trend in vessel wall thickness, internal diameter, and construction (smooth muscle )
The bigger the vessel (artery/vein), the thicker the wall and diameter, arteries are high elastic, while veins are highly compliant. The smaller the vessel (capillaries), the thinner the walls and the fewer the muscles. More compliant, but highly precise on vasodilation.
What are arteries generally considered? Why?
A pressure reservoir.Arteries need to maintain pressure. Aorta expands as blood flow in. The aorta is somewhat compliant. Force is released, elasticity brings the vessel back to the original shape as it pushes blood down the line.
<p>Compliance and elasticity.Define ComplianceDefine Elasticity.How are they related?</p>
<p>Compliance--the ability of a material to stretch when placed under an external forceElasticity--the ability of a material to return to its normal shape when an external force is released.Compliance and elasticity are inversely related.</p>
Define Distending Pressure
To swell out or expand from or as if from internal pressure.
What is the equation for Compliance?
^V/^Distending P
What do arterioles regulate?
Regulate total peripheral resistance
What is arteriole compliance compared to arteries?
How are they innervated?
What does the smooth muscle do?
What percentage of Total Peripheral Resistance (TPR) do arterioles contribute?
Much LESS compliant than arteries, but dilation can be highly regulated.
Highly innervated by the autonomica nervous system–sympathetic system specifically.
Abundant smooth muscle layer allows for considerable ability to contract or relax.
60% of TPR is attributable to arterioles.
How is arteriole resistance regulated intrinsically?
How is arteriolar resistance regulated extrinsically?
The radius in certain tissues and organs have Intrinsic regulation of arteriolar radius regulates distribution of blood flow to tissues and organs by affecting arterial radius in tissue and organ. ex. mechinisms produced internally contract and expand.
Whole body…whole body DF…Extrinsic regulation of arteriolar radius regulates MAP. Initiation of regulation comes from outside what is regulated. ex. Autonomic Nervous System.
Define Mean Arterial Pressure
Define Perfusion Pressure
when are they the same thing?
MAP–the pressure gradient across the entire systemic circulation
Perfusion Pressure–pressure gradient across a single organ or tissue.
(for a systemic organ, MAP and perfusion pressure are essentially equal.
Intrinsic Control of Arteriolar Radius.
What is the pressure gradient for all organs and tissues?
How do differences in resistance across different organs come about?
What is the equation for Organ Blood Flow?
Flow through each organ and tissue is driven by the same pressure gradient—MAP
Differences in flow must then result from differences in resistance.
Organ BF = ^P / Organ R (2nd law)
What causes changes in relative blood flow?
How is arteriolar resistance changed?
Changes in relative organ blood flow (% of CO) are primarily due to changes in arteriolar resistance within each organ.
Arteriolar resistance is altered by contraction or relaxation of smooth muscle in walls of the arterioles.
Intrinsic control of vascular smooth muscle does what?
What 4 things do vascular sm respond to?
Regulates the diameter of arterioles in tissues and organs
Responds to:
- Changes in organ metabolic activity.
- Changes in organ blood flow
- Stretch of arteriolar smooth muscle
- Local chemical messengers.
