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19 Cards in this Set

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What is achieved by unilateral carotic occlusion?
Decreased carotid sinus pressure which prompts a responsive increase in MAP
How does carotic occlusion cause an increased MAP?
-Decreased rate of firing caused by decreased stretch of stretch receptors
-Decreased PNS output; increased SNS output -> incr HR/contractility and circulatory vasoconstriction.
3 Effects of increased SNS:
1. increased HR
2. increased contractility
3. increased TPR
Why doesn't unilateral carotic occlusion increase MAP as much as bilateral?
Because buffering is achieved by the remaining carotid sinus and the aortic baroreceptors.
What happens when the unilateral occlusion is released?
Undershoot and overshoot of MAP due to a percieved increased pressure in the carotid sinuses.
Why doesn't MAP decrease in response to the increased CO when people exercise?
Because the baroreceptors reset themselves.
How is a bilateral carotid sinus occlusion different from unilateral?
The increase in MAP will be bigger and oscillation after release may be larger.
What happens when you occlude IVC and SVC?
-Decrease venous return
-Decr preload -> contractility
-Decrease MAP
What is the baroreceptor response to IVC/SVC occlusion?
Detects decreased MAP so decreases firing; reduces PNS outflow and increases SNS outflow to bring MAP back up
What happens when IVC/SVC occlusion is released?
All of a sudden VR increases again; filling of heart increases contractility, SV, BP.
What happens when the Aorta is occluded?
-Afterload acutely increased
-BP below occlusion decreases
-BP before occlusn increases
What is the response to BP changes after aortic occlusion?
The aortic baroreceptors just before the occlusion see an increased BP so they decrease SNS and increase PNS
Results of Aortic occlusion effects on circulation:
-Vasodilation
-Decreased HR
-Decreased contractility
How is nonneural effect of aortic occlusion different from neural?
The neural decrease in heart contractility is masked by the decreased ejection fraction which causes increased stroke volume so incr contractility.
Why does the aortic pressure waveform have a characteristic appearance?
Because the pressure values and wave configurations are altered during transmission thru the arterial tree.
What happens to the aortic pressure waveform with increasing distance from the aorta?
1. Dicrotic notch lessons and waves may appear in it.
2. Pulse pressure increases
Why does pulse pressure increase w/ distance form the aorta?
Because pulse waves summate
Why may waves develop in the dicrotic notch of aortic pressure waveform?
Because of resonant oscillations in the elastic arteries caused by the ejected volume bolus.
What is the effect of a sudden 50 mL injection of volume?
-Suddenly VR increases
-EDV increased - so increased contractility, stroke volume, and MAP.