Flashcards in Local Regulatory Mechanisms Deck (28)
What are the resistance vessels?
How is vascular smooth muscle related to the blood flow?
Vascular smooth muscle is responsible for the control of total peripheral resistance, arterial and venous tone, and the distribution of blood flow throughout the body.
What is auto regulation in regards to blood flow?
It is the intrinsic property of an organ or tissue to maintain constant blood flow
despite changes in arterial perfusion pressure.
What are the central controls of blood flow?
What are the local controls of blood flow?
Describe the effects of auto regulation as the arterial pressure increases abruptly from the baseline.
Autoregulation will increase the resistance to the blood flow which will gradually bring the arterial pressure back to the baseline.
Does auto regulation regulate the blood flow?
Does auto regulation regulate the pressure?
NO! Only indirectly by controlling the blood flow through the amount of resistance
Does arterial pressure determine the capillary hydrostatic pressure?
Not significantly because of the drastic drop and the arteriole control of the pressure.
How does auto regulation function at very low and very high pressures?
Autoregulation only works at a defined pressure range and it will fail at very low or very high pressures.
What organs have strong auto regulation?
What organs have weak auto regulation?
What organs have little auto regulation?
Why do the lungs have so little auto regulation?
Lungs have no autoregulation as you need 100% blood flow there when output increases. You do not want auto regulation decreasing the blood flow to the lungs when the pressure is increasing.
What are the myogenic mechanisms of auto regulation of blood flow?
Smooth muscle contracts in response to stretch and relaxes in response to the reduction of stretch.
An increase in pressure causes an initial stretch of the vessel wall which in turn causes the vascular smooth muscle to contract (vasoconstrict), resulting in an increase in resistance and decrease in flow.
A decrease in pressure causes a reduction in stretch of the vessel wall which in turn causes the vascular smooth muscle to relax (vasodilation) resulting in a decrease in resistance and increase in flow.
What are the metabolic mechanisms of auto regulation of blood flow?
Metabolic activity generates metabolites that relax smooth muscle.
Pressure increases increase blood flow which will remove the metabolites and allow for vasoconstriction, which will increase the resistance and reduce flow.
Conversely, when pressure is decreased less blood flow allows an accumulation of inhibitory metabolites causing vessels to dilate. Dilation decreases resistance and increases flow.
Does auto regulation depend on the activity of endothelial cells?
Describe endothelial regulation of blood flow.
With increased blood flow through a vessel, the shear stress on it will be increased and the endothelium will release EDRF/NO for
vasodilation of the vessels
Describe metabolic regulation of blood flow.
Metabolites released locally act to dilate the tissue and increase blood flow to it. Reduction in oxygen delivery can also lead to the formation of metabolites that are vasodilators.
Describe active hyperemia.
As tissue activity increases, the blood flow to that tissue will increase as well due to the metabolites that are produced as a result.
Describe reactive hyperemia.
Transient increase in blood flow that follows a period of arterial occlusion and it occurs due to the accumulation of metabolic debt.
What happens to the reactive hyperemic response as the time of the arterial occlusion increases?
The response will become greater the more time that the occlusion has occurred for.
What is shock?
It is where there is inadequate perfusion to the body.
What is cardiogenic shock?
Caused as a result of heart damage, often due to MI
What is hypervolemic shock?
There is inadequate blood volume due to blood loss.
What is anaphylactic shock?
It is a systemic allergic reaction that can cause death with respiratory obstruction.
What is septic shock?
Immune response occurs from severe infection.