Controlling regional blood flow Flashcards
How does pressure affect control of blood flow?
We need sufficient pressure to be able to control the flow
If we have low pressure there is lack of control of flow
Pressure gives us the drive to push things around a circuit but also gives us control of how much we want to be pushed out
Q=∆P/R
How is blood distributed to all organs in the cardiac circuit?
Within the series circuit we get a parallel circuit, the blood is divided up into a continuous branching of arterial network so it can be distributed all over the body so we can get regional flow and supply the different organs with the amounts of blood they need
Right and left heart are in series
Regions that blood goes to are in parallel
How is blood distributed at rest?
At rest we distribute the 5L of blood into the lungs and back to the left side of the heart where it then is divided into different regions of the body (e.g. brain, kidneys, muscle, skin etc.) and it is then transferred back to the right side of the heart - no blood is lost or gained but the amount of oxygen in the blood changes (volume of blood does not change)
How is blood distributed during exercise?
When we exercise different parts of the body do more or less work so we need to send some blood to one place and less to another
Amount of blood distributed always stays the same in the brain; skeletal muscle, skin and heart normally increase greatly with exercise; kidney, GI tract and other tissues decrease
Blood is diverted to the places it needs to go - divergent flow depending on metabolic needs
How is MAP controlled during exercise?
Increase cardiac output means decreased TPR (vasodilation) so that mean arterial pressure can stay constant
Decreased TPR means we dilate the pipes wider so more blood can flow through - decreased resistance
Why is blood flow increased in some regions of the body and decreased in others?
When you exercise muscles need more blood hence increased flow and decreased TPR. You don’t need to make urine while exercising hence in the kidneys you decrease flow hence resistance is increased
How do arterioles control regional flow?
Arterioles connect supply arteries with capillary bed and have lots of vascular smooth muscle which can contract or relax changing the amount of resistance in the blood flow
Arterioles are the resistance vessels, arteries are the delivery vessels, capillary are the business vessels
Vessel radius and resistance to blood flow
Luminal radius bigger (vasodilate) = less resistance, more flow
Luminal radius smaller (vasoconstrict) = more resistance, less flow
R= 1/r^4 = 1/(0.5d)^4 resistance is inversely proportional to radius
What do different tones and radius mean for controlling blood flow?
Tone - is it contracted, relaxed or normal, adjusted to control blood flow
Relaxed = dilated (large) diameter
Normal = normal diameter
Contracted = constricted (small) diameter
