venous return and starlings law

Question 1

where do veins carry blood

Answer 1

towards the heart

Question 2

what blood do they carry

Answer 2

deoxygenated blood

Question 3

what is the structure of a vein

Answer 3

no stretch, thin layer of smooth muscle
thin walled large lumen have valves to prevent backflow

Question 4

what is venous return

Answer 4

return of blood to the right side of the heart via the vena cava
- up to 70 % of the total volume of blood is contained in the veins at rest
- large amount of blood can be returned to the heart when needed
- during exercise amount of blood returning to the heart increases
- meaning if more blood is being pumped back to the heart, then more blood has to be pumped out so stroke volume will increase= starlings law

Question 5

under normal circumstances…

Answer 5

venous return = stroke volume (what goes in comes out)

Question 6

what are the 6 venous return mechanisms

Answer 6

• the skeletal muscle pump
• the respiratory pump
• pocket valves or valves
• smooth muscle in the walls of veins
• gravity
• the suction pump action of the heart

Question 7

the skeletal muscle pump

Answer 7

• when muscles contract and relax they change shape, this shape change means that muscles press on the nearby veins and cause a pumping effect and squeeze the blood towards the heart

Question 8

the respiratory pump

Answer 8

when muscles contract and relax during breathing in and out, pressure changes occur in the thoracic (chest) cavity and the abdominal (stomach) cavity

Question 9

pocket valves

Answer 9

important that blood in the veins only flow in one direction, presence of valves ensures that this happens, this is because once the blood has passed through the valves, they close to prevent the blood flowing back

Question 10

what are the other 2 factors that aid venous return

Answer 10

• a very thin layer of smooth muscle in the walls of the veins. helps squeeze blood back towards the heart
• gravity helps the blood return to the heart from the upper body

Question 11

why is it important to maintain venous return during exercise

Answer 11

to ensure the skeletal muscles are receiving enough oxygen to meet the demands of the activity
- during exercise, demand for oxygen is greater and heart is beating faster so vascular system has to help out too
- now skeletal muscle pump and respiratory pump are needed to ensure venous return is maintained

Question 12

what does an active cool down do

Answer 12

keep the skeletal muscle pump and respiratory pump working, therefore preventing blood pooling

Question 13

what is blood pooling

Answer 13

blood collecting in the veins

Question 14

blood pressure during exercise

Answer 14

important to increase blood flow through the circulatory system so the muscles receive the oxygen they require. an increase in blood pressure can achieve this

Question 15

what is blood pressure

Answer 15

force exerted by the blood against the blood vessel wall

Question 16

systolic pressure

Answer 16

pressure in the arteries when the ventricles are contracting

Question 17

diastolic pressure

Answer 17

pressure in the arteries when the ventricles are relaxing

Question 18

blood pressure formula

Answer 18

blood flow x resistance

Question 19

where is blood pressure measured

Answer 19

at the brachial artery in the upper arm, a typical reading at rest is 120mmHg/80 (millimetres of mercury)

Question 20

what is blood pressure largely dependant on

Answer 20

the distance of the blood vessel from the heart, the low pressure of blood in the veins means that mechanisms are needed to pump the blood back to the heart

Question 20

what is blood pressure largely dependant on

Answer 20

the distance of the blood vessel from the heart, the low pressure of blood in the veins means that mechanisms are needed to pump the blood back to the heart

Question 21

impact of blood pressure on venous return

Answer 21

when systolic pressure increases, there is also an increase in venous return and when systolic pressure decreases there is a decrease in venous return