Lecture 10 - Venous blood flow and the heart Flashcards
Where is most blood found?
Small veins and venules
How do veins store more blood at lower pressure? 2 things
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What is compliance
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What’s the formula for compliance
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How does compliance in arteries and veins differ?
Veins = thin walls, not much muscle so small change in pressure = large change in shape (high compliance)
i.e. increase pressure, you increase volume
Arteries = thick muscular wall so doesn’t change shape much (low compliance)
i.e. increase pressure, don’t increase volume that much
What happens when arterial puncture and loss of arterial blood (loss in arterial pressure)?
Blood transfusion from venous to arterial system - vent constriction (pushes blood through). The pressure in veins increases due to this so the stored blood can be sent to arteries
High vascular compliance means that blood tends to……
- Venous volume is….
- While supine……
- In upright position…….
accumulate (pool) in veins
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What two things counteract venous pooling
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What cuspid are the venous valves?
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How does skeletal muscle counteract venous pooling?
Muscle tone acts to stiffen the veins - makes them less compliant and prone to pooling
Skeletal muscle pump affects what to the heart?
Venous return
It squeezes veins and that increases pressure so blood flow through veins and this increase veinous return
What kind of muscles affect veinous return?
Diaphragm, intercostal too - not just arms and legs. So exercise + breathing heart = increase veinous return.
Increased venous return means increased…..
Stroke volume
What’s Starling’s Law of the Heart?
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Stretched sarcomeres will lead to
stronger contraction but only till there’s overlap between actin and myosin
