lecture 12 Flashcards
What has the greatest distribution of blood?
Veins, in particularly veins and venules
Why do veins have the greatest distribution of blood?
They have the ability of act as capacitance vessels and is stored at a low pressure
What percentage of the blood is systemic venous system?
64%
How do veins store more blood at a lower pressure?
Thin walls = more compliance
compliance =?
change in volume / change in pressure
A small change in volume in veins =
large change in pressure
A small change in volume in arteries =?
large change in pressure
What is starling’s law of the heart?
The more stretched the muscle fibres are before a contraction, the stronger the contraction will be
what is compliance?
the extent to which a vessel allows deformation in response to changes in pressure
What do veins do in response to major blood loss?
Vasoconstrict to cause an increase in blood arterial circulation
In an upright position where does the increase in venous volume go?
below the heart due to gravity
What are the two ways to counteract venous pooling when standing?
Venous valves
skeletal muscle
What are venous valves?
valves that counteract the pooling and prevent blood flow back down the legs
How does skeletal muscle counteract venous pooling
the muscle tone stiffens veins to make them less compliant and less prone to pooling
What increases the preload on the heart?
venous return
