Local Regulatory Mechanisms Flashcards
What are the resistance vessels?
Arterioles
Precapillary sphincters
Metarterioles
Venules
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?
Neural
Hormonal
What are the local controls of blood flow?
Myogenic
Metabolic
Endothelial
Mechanical
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?
Yes
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?
- Heart
- Brain
- Kidney
- Skeletal Muscle
What organs have weak auto regulation?
-Splanchnic Circulation
What organs have little auto regulation?
- Skin
- Lungs
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.
