HUBS192 Lecture 12 - Venous Blood Flow and the Heart Flashcards
why is it important for more blood to be stored in the body than required?
incase of an injury that results in blood loss that results in reaching a certain point where mean arterial blood pressure can no longer be maintained
where is the extra blood stored in the body?
small veins and venules store the extra blood circulating in our system
what are arteries in terms of pressure and volume?
low volume of blood at a high pressure
what are veins in terms of pressure and volume?
high volume of blood at a low pressure
what is compliance?
the extent to which a vessel allows deformation in response to an applied force
-how much does it distend or expand when pressure increases?
what are 2 features to the structure of an artery?
thick wall makes an artery rigid
what are 2 features to the structure of a vein?
thin wall makes a vein compliant
what is the equation for compliance?
compliance= ΔV/ΔP
what is an example of a compliant object? and does this object represent an artery or a vein?
a ballon
-represents a vein
what is an example of a non-compliant object? and does this object represent an artery or a vein?
rubber tube (they will not change shape) -represents an artery
what is the relationship between veins and compliance?
veins are highly compliant vessels
what does it mean that veins have “survival value”?
blood can be transported from veins to the arteries in an emergency situation
what is venoconstricton?
constriction of veins where the squeezing of the vein pushes extra blood up and through the heart to be pumped back out into the arteries ultimately increasing mean arterial blood pressure
what does high vascular compliance mean?
means that blood tends to accumulate (pool) in veins
how does gravity affect venous volume in a supine (laying down) position?
while supine (laying down) venous volume is uniform from head to toe
what does supine mean?
laying down
how does gravity affect venous volume in the upright position?
in the upright position, venous volume below the heart increases; whereas venous volume below the heart decreases that causes extreme venous pooling in the legs and feet
what are the structures that prevent extreme venous pooling in the legs and feet and how do they function?
venous valves counteract venous pooling that discontinues the column blood by more evenly distributing weight
what are the 2 structure that prevent venous pooling?
1) venous valves
2) ‘tone’ of surrounding tissue
how does the ‘tone’ of surrounding tissue prevent venous pooling?
- skeletal muscle because it can alter its tensile state
- muscle tone acts to stiffen the veins which makes them less compliant and prone to pooling
what is the relationship between the location of veins and muscle ‘tone’?
veins are located on top of muscles therefore the ‘tone’ of the muscle controls and counteracts venous pooling within veins
what is the relationship between skeletal muscle contractions and ‘venous return’?
skeletal muscle contraction increase ‘venous return’ to the heart
-the valves superior to the contracting muscle open, allowing blood to move toward the heart
what is Starling’s law of the heart?
the more stretched muscle fibres are before a contraction, the stronger the contraction will be by an increased venous return means increased stroke volume
why does the heart contract stronger if there is a larger volume of venous return?
when you pump more blood into the heart, the heart and the myocytes expand, therefore the sarcomere is pulled further apart and stretched out therefore the further apart the sarcomere the stronger the contraction, greater stroke volume and increased cardiac output
