HRR: peripheral circulation Flashcards
How does increased resistance impact flow?
It reduces it.
What are myogenic mechanisms of altering smooth muscle tone?
A local regulation that can cause vessel diameter change; increased flow causes a stretch in the vessel wall, causing a stretch in the smooth muscle wall. The smooth muscle will send signals to the vessel to constrict. This increases resistance and decreases flow.
What is the metabolic mechanism for regulating vascular tone?
Concentrations of molecules produced by metabolic activity can regulate blood vessel diameter; things like high CO2, lactate, and protons cause dilation.
Is potassium a vasodilator or vasoconstrictor locally?
Vasodilator.
Does adenosine act as a local vasodilator or vasoconstrictor?
Vasodilator.
What are some examples of endothelial vasoconstrictors?
Endothelin-1 and thromboxane.
What are some examples of endothelial vasodilators?
PGI2 and NO.
What do endothelial vasoconstrictors activate to promote constriction?
PLC.
What are extrinsic regulators of vessel size?
The SNS and PSNS.
What is the effect of norepinephrine on vessels?
It activates PLC which causes vasoconstriction.
How does acetylcholine lead to dilation?
NO release.
What is the main region associated with central regulation?
The vasomotor region.
What are major input regions for the vasomotor area?
Baroreceptors, chemoreceptors, visceral organs.
Vasomotor inhibition leads to…
Vasodilation.
Vasomotor activation leads to…
Vasoconstriction.
Does a low blood pressure increase activate or inactivate VR?
Inactivate.
Does lung inflation activate or inactivate VR?
Inactivate.
How does epinephrine impact vessel diameter?
At low doses it will cause dilation, and at high doses it acts as a vasoconstrictor.
How does vasopressin impact vessel diameter?
Vasoconstriction via PLC.
How does Ang II impact vessel diameter?
Vasoconstriction via PLC.
What is autoregulation?
Organs have intrinsic mechanisms to prevent massive flow changes when pressure changes occur. There will be an initial change, but an organ can use intrinsic mechanisms to return to steady state.
What is active hyperemia?
Blood flow picks up due to dilation during exercise in order to maintain activity.
Describe cutaneous circulation.
As the body warms, blood can be sent to the skin to dissipate the heat and cause sweating, both of which will lower core body temp.
What is reactive hyperemia?
Releasing an occluded vessel will result in an overshoot of flow after restoration; the longer the occlusion, the higher the jump in flow.
Which organs are under strong intrinsic control?
Brain, heart, skeletal muscle.
Which organs are under strong extrinsic control?
Kidneys, splanchnic organs, skin.
Describe the CNS ischemic response.
Decreased flow to the brain causes an increase in sympathetic activation, resulting in major vasoconstriction and cardiac acceleration. This preserves flow to the heart and brain at the expense of other systems.
