Lecture 12 Flashcards
why are we able to lose some blood and still be fine?
we have a reserve
- excess blood in the venous circulation
where is most of the blood in our body found at one given time
in the systemic venous system
why is there not as much blood in the arteries as there is in the veins at one time
cause the pressure would be too high
arteries have thick walls, what does this mean in terms of compliance
arteries are rigid, they will not readily stretch like veins so will not store excess blood
what is compliance
the extent to which a vessel allows deformation in response to an applied force
veins have thin walls, what does this mean in terms of compliance
veins are compliant, they will readily stretch to store excess blood (they will dilate)
what is compliance dependent on
change in volume / change in pressure
what is the compliance equation in terms of arteries
small volume / large pressure = low compliance
what is the compliance equation in terms of veins
large volume / small pressure = high compliance
what is the venous volume like when you are lying down
uniform from head to toe
in the upright position what is the venous volume like
- volume below the heart increases
- volume above the heart decreases
what do valves in the veins do
stop pooling, keeps the blood going forward
what does tone of muscles mean
how tense at rest
what does muscle tone do in muscles
stiffen the veins, makes them less compliant and prone to pooling
what is starlings law of the heart
more you fill it the more it squirts
- volume increases, so does stroke volume
