Lecture 3: Vascular Reactivity Flashcards
The arterial system converts ___________ or ___________ outflow from the heart into a steady flow of blood through the ____________
Intermittent or Pulsatile
Capillaries
Flow velocity is _________ proportional to the cross sectional area of all the blood vessels in a given part of the vascular tree
Inversely proportional
As we move away from the heart what happens to the elasticity of the vessels?
They become less elastic
Why do the aorta and large vessels have large diameters and high elasticity?
Allows them to handle large volumes of blood and propel them along the vessels
Arterioles are high ___________ vessels with a relatively large amount of __________.
Resistance
Smooth Muscle
What is the Windkessel effect?
Elastic vessels can expand when blood volume increases and then recoil to help propel blood along
Blood flows ________ in the capillaries to facilitate gas exchange
slowly
How do we calculate the rate of blood flow?
F=ΔP/R
F = flow rate
P = pressure
R = resistance
What is axial streaming?
During fast blood flow, RBC congregate in the center of the vessel to reduce resistance or frictional force caused by collisions with the vessel walls
In healthy blood vessels, blood flow is _________ and flow is faster in the _______.
Laminar
Center
What is blood pressure?
The force exerted against a vessel wall, it depends on the volume of blood and the vessel compliance
What is pulse pressure?
PP = SBP-DBP, it is directly affected by stroke volume and vessel compliance
Why does SBP increase?
Blood is ejected into the aorta by the left ventricle
Why does DBP decrease?
Due to peripheral run-off from the arteries to the microcirculation
What are the formulas for Mean Arterial Pressure?
MAP = 2/3 DBP + 1/3 SBP = DBP + 1/3 PP
Kortkoff sounds occur when there is _______________ through the vessels after it is no longer occluded
Turbulent blood flow
Vessels compliance ____________ with age
decreases
Why can we control the flow through the microcirculation?
Lots of smooth muscle in the arterioles
What causes vasoconstriction?
↑ myogenic activity ↑ P O2 ↑ Sympathetic stimulation ↓P CO2 Changes in the endothelium
What causes vasodilation?
↑ P CO2 ↑ NO ↓myogenic activity ↓ P O2 ↓ Sympathetic stimulation
What is flow-mediated dilation (FMD)?
Blood flow exerts a shear stress on the vessel wall this causes vasodilation via NO
What causes NO release
Shear stress leads to the activation of endothelial Nitric Oxide Synthase (eNOS) via mechanotransduction.
In the endothelium eNOS converts __________ to NO
L-Arginine
In the smooth muscle, NO causes _____ to convert GTP to _______.
sGC
cGMP
How does increasing age affect NO?
↓ NO production and ↑ NO breakdown
What is active hyperaemia?
↑ blood flow caused by metabolic changes associated with ↑ muscle activity (Exercise –> ↓ P O2 –> vasodilation –> ↓ Resistance –> ↑ flow)
What is reactive hyperaemia?
↑ Blood flow caused by metabolic changes associated with vessels occlusion. Blood flow ↑ after occlusion to remove metabolites that have accumulated (magnitude is proportional to the duration of occlusion)
What is Autoregulation?
myogenic response to stretch, ↑ stretch –> vasoconstriction
Autoregulation allows __________ regardless of a change in ____.
stable flow
MAP
