HUBS192 Lecture 12 - Venous Blood Flow and the Heart

Question 1

why is it important for more blood to be stored in the body than required?

Answer 1

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

Question 2

where is the extra blood stored in the body?

Answer 2

small veins and venules store the extra blood circulating in our system

Question 3

what are arteries in terms of pressure and volume?

Answer 3

low volume of blood at a high pressure

Question 4

what are veins in terms of pressure and volume?

Answer 4

high volume of blood at a low pressure

Question 5

what is compliance?

Answer 5

the extent to which a vessel allows deformation in response to an applied force
-how much does it distend or expand when pressure increases?

Question 6

what are 2 features to the structure of an artery?

Answer 6

thick wall makes an artery rigid

Question 7

what are 2 features to the structure of a vein?

Answer 7

thin wall makes a vein compliant

Question 8

what is the equation for compliance?

Answer 8

compliance= ΔV/ΔP

Question 9

what is an example of a compliant object? and does this object represent an artery or a vein?

Answer 9

a ballon

-represents a vein

Question 10

what is an example of a non-compliant object? and does this object represent an artery or a vein?

Answer 10

rubber tube (they will not change shape)
-represents an artery

Question 11

what is the relationship between veins and compliance?

Answer 11

veins are highly compliant vessels

Question 12

what does it mean that veins have “survival value”?

Answer 12

blood can be transported from veins to the arteries in an emergency situation

Question 13

what is venoconstricton?

Answer 13

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

Question 14

what does high vascular compliance mean?

Answer 14

means that blood tends to accumulate (pool) in veins

Question 15

how does gravity affect venous volume in a supine (laying down) position?

Answer 15

while supine (laying down) venous volume is uniform from head to toe

Question 16

what does supine mean?

Answer 16

laying down

Question 17

how does gravity affect venous volume in the upright position?

Answer 17

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

Question 18

what are the structures that prevent extreme venous pooling in the legs and feet and how do they function?

Answer 18

venous valves counteract venous pooling that discontinues the column blood by more evenly distributing weight

Question 19

what are the 2 structure that prevent venous pooling?

Answer 19

1) venous valves

2) ‘tone’ of surrounding tissue

Question 20

how does the ‘tone’ of surrounding tissue prevent venous pooling?

Answer 20

• 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

Question 21

what is the relationship between the location of veins and muscle ‘tone’?

Answer 21

veins are located on top of muscles therefore the ‘tone’ of the muscle controls and counteracts venous pooling within veins

Question 22

what is the relationship between skeletal muscle contractions and ‘venous return’?

Answer 22

skeletal muscle contraction increase ‘venous return’ to the heart
-the valves superior to the contracting muscle open, allowing blood to move toward the heart

Question 23

what is Starling’s law of the heart?

Answer 23

the more stretched muscle fibres are before a contraction, the stronger the contraction will be by an increased venous return means increased stroke volume

Question 24

why does the heart contract stronger if there is a larger volume of venous return?

Answer 24

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