Microcirculation, Coronary Circulation, Myocardial Oxygen consumption Flashcards
The Sterling Equation calculates the flow of which substance(s)?
Calculates the flow of water. It is dependent of the net forces influencing the movement of water.
Blood flow through the capillaries is regulated by contraction and relaxation of ___ and ___.
Arterioles and precapillary sphincters.
How do lipid-soluble substances cross the membranes of the capillary endothelial cells?
Simple diffusion.
How do water, glucose, and amino acids cross the capillary?
Via the water-filled clefts between the endothelial cells.
What does the Starling equation measure?
Measures fluid exchange across capillaries.
What is the Starling equation?
J(v) = K (f) [ (Pc-Pi)-(πc - πi)]
Jv = Fluid movement Kf = hydroaulic conductance (constant) Pc = capillary hydrostatic pressure Pi = interstitial hydrostatic pressure πc = capillary oncotic pressure πi = interstitial oncotic pressure
When Jv is positive, the net fluid movement is ____.
out of the capillary.
Net fluid movement out of the capillary is defined as _____.
Filtration
When Jv is negative, net fluid movement is ____.
into the capillary
Net fluid movement into a capillary is defined as ____.
absorption
An increase in Pc favors ____.
Filtration
How does the Pc change if arterial or venous pressure is increased?
Pc is also increased.
What is the normal value of Pi?
0 mm Hg (can be slightly negative)
How does an increase in Pi affect filtration?
opposes filtration.
How does an increase in πc affect filtration?
oppose filtration
How does an increase in πi affect filtration?
favors filtration
Factors that increase filtration:
- ___Pc
- ___Pi
- ___πc
- ___πi
- Increased
- Decreased
- decreased
- Increased
You calculated the Starling equation and your answer is +6 mm Hg. Will filtration or absorption take place?
Filtration will occur.
What are some examples of local (intrinsic) control of blood flow?
a. Autoregulation (by need) seen in heart, brain, and kidney
b. Active hyperemia - proportional to metabolic activity of that organ
c. Reactive hyperemia - occurs after a period of occulsion
What is the myogenic hypothesis?
Mechanism explaining local control.
-Based on the idea that vascular smooth muscle contracts when it is stretched. This maintains a constant flow.
What is the metabolic hypothesis of local control of blood flow?
- based on the idea that tissue supply of O2 is matched to tissue demand for O2.
When metabolic activity in tissue is increased, what kind of metabolites are produced? Vasodilator or constrictor? Give examples
Vasodilator metabolites, like CO2, H+, K+, lactate, and adenosine.
Give an example of a extrinsic control of blood flow.
Hormonal: sympathetic innervation, vasoactive hormoens like histamine, bradykinin, serotonin, and protaglandins.
Histamine and bradykinin causes: __1__dilation and __2__ constriction, resulting in __3__ Pc and thus __4__ filtration. Net result __5__.
- Arteriolar
- Venous
- Increased
- increased
- Local edema
Coronary circulation is controlled mainly by____.
Local metabolic factors.
What is the most important local vasodilator for the cerebral circulation?
Cerebral circulation is almost entirely controlled by local metabolic factors like Co2 which acts as a vasodilator to increase blood flow to the brain.
Name two ways skeletal muscle blood flow is regulated.
- sympathetic innervation - alpha receptors - vasoconstriction - during rest. beta 2 receptors- vasodilation during fight or flight response.
- Local metabolic control. local vasodilator substances like lactate, adenosine, and K are produced after exercise .
Blood flow to the skin: the principal function of the cutaneous sympathetic nerves is for __1___ regulation.
- temperature
