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20 Cards in this Set

  • Front
  • Back
What occurs during Late Diastole? 1st stage of heart cycle
All chambers relax and fill with blood
What occurs during Atrial Systole? 2nd stage of heart cycle
Atria contract, and add 20% more blood to ventricles
What happens during Isovolumic Ventricular Contraction? 3rd stage of heart cycle
the AV valves close, ("lub") and pressure build
What happens during Ventricular Ejection? 4th stage of heart cycle
Semilunar valves are pushed up open, and blood is forced out
What happens during Ventricular Relaxation? 5th stage of heart cycle
Back flow from aorta closes Semilunar valves; AV valves open and refilling starts
What 3 factors seem to contribute to vasodilation?
1. Active Skeletal Muscle fibers
2. Endothelial Cells
3. RBC's
What is conducted vasodilation?
When arterioles were dilated by application of Acetylcholine, the feed arteries also dilated
Why is this important?
conduciton of electricl signals between endothelial and or smooth muscle cells via gap junctions
What is it dependent upon?
Nitric Oxide and ATP-sensitive Potassium channels
*this also appears during skeletal muscle contractions
What is flow-mediated dilation?
when flow increases, vessels dilate
What happens with increased flow?
Endothelial cells expreience shear stress on their walls, and release NO, prostacyclin, and EDHF
Why is it thought that Oxygen could be a vasodilator?
by decreasing oxygen you decrese ATP in smooth muscle cells which causes relaxing factors to be released causing dilation of arterioles
What's the problem?
Vasculature responds to hypoxia but oxygen delivery insn't primary controller of blood flow to active muscle
Why is it thoguht that Lactate is a Vasodilator?
Lactate increases N.O. which binds to Guanylate Cyclase, that converts GTP to cGMP causing vascular smooth muscle relaxation
What's the problem?
Muscle blood flow is icnreased at low intensities of exercise at which lactate change is minimal in interstitial fluid
Why is Adenosine thought to be a possible vasodilator?
Adenosine binds to adenosine receptor sites on vascular and smooth muscle cells. This binding causes smooth muscle relaxation and arteriole dilation
What's the problem?
There are conflicting results of adenosine in the incresed bloood flow to skeletal muscle during exercise. It was never confounded what effects of adenosine receptor blockage did to exercise muscle blood flow in dogs
Why is Potassium considered to be a potent vasodilator?
Potassium is ejected from skeletal muscle during muscular contraction causing influx in interstitial space. This activates Na/K ATPase pump and K enters smooth muscle flushing Ca out and ultimately relaxing smooth muscle causing dilation
What's the problem?
There isn't enough evidence overtime to say that this is the cause of immediate vasodilation
Why are H+ ions considered to be immediate vasodilators?
Lowering of pH (which is increasing H+ ions) via CO2 can lower Ca+ concentration which results in smooth muscle relaxation