Control of Cardiac Output

Question 1

what is afterload

Answer 1

the pressure in the wall of the LV during ejection

Question 2

what is preload

Answer 2

the amount the ventricles are stretched during diastole

Question 3

what is the total peripheral resistance

Answer 3

resistance to blood flow

Question 4

which blood vessels offer the greatest resistance to blood flow

Answer 4

arterioles

Question 5

what happens to arterial and venous pressure if total peripheral pressure decreases

Answer 5

arterial pressure decreases but venous pressure increases

Question 6

what happens to arterial and venous pressure if total peripheral pressure increases

Answer 6

arterial pressure increases but venous pressure decreases

Question 7

what happens to arterial and venous pressure if cardiac output increases

Answer 7

arterial pressure increases but venous pressure decreases

Question 8

what happens to arterial and venous pressure if cardiac output decreases

Answer 8

arterial pressure falls but venous pressure rises

Question 9

true or false; narrowing the arterioles increases blood flow

Answer 9

false.

Question 10

true or false constricting arterioles increases arteriole pressure but decreases venous pressure

Answer 10

true

Question 11

true or false; constricting arterioles increases resistance

Answer 11

true

Question 12

what happens to the arterioles and precapillary sphincters if tissues need more blood

Answer 12

they will dilate

Question 13

what happens to the heart rate if the peripheral resistance falls

Answer 13

pumps more so that the arterial pressure doesn’t fall and venous pressure doesn’t rise

Question 14

what are the 2 mechanisms of how the heart changes to control arterial and venous pressure

Answer 14

intrinsic and extrinsic

Question 15

what is the intrinsic mechanism of heart response

Answer 15

where the heart response if due to factors within the heart

Question 16

what is the extrinsic mechanism of the heart response

Answer 16

where the heart responds to factors outside of the CVS e.g. the ANS

Question 17

what is cardiac output equal to

Answer 17

stroke volume x heart rate

Question 18

what is the stroke volume

Answer 18

end diastolic volume - end systolic volume

Question 19

what is the end diastolic volume of a normal heart

Answer 19

120ml

Question 20

what is the LV pressure of a normal heart at the end diastolic volume

Answer 20

10 mmHg

Question 21

what is the normal stroke volume

Answer 21

70 ml

Question 22

what does the Frank-Starling Law state

Answer 22

as the heart fills more, it contracts harder and so the stroke volume increases

Question 23

what must happen to the venous pressure to allow the heart to fill more

Answer 23

it increases

Question 24

what happens to contraction there is too much overlap of filaments in a sarcomere

Answer 24

the cell cant contract well

Question 25

what happens when the filaments in a sarcomere are stretched

Answer 25

the cell can contract better

Question 26

what happens to calcium sensitivity as cardiac muscle fibres are stretched

Answer 26

it increases

Question 27

is the frank starling mechanism an intrinsic or extrinsic control mechanism

Answer 27

intrinsic

Question 28

what is the mechanism by which increasing the filling of the heart increases stroke volume

Answer 28

Frank-Starling mechanism

Question 29

what does it mean by saying the pulmonary and systemic circulations operate in series

Answer 29

same volume of blood pumped to the body must also be pumped to the lungs

Question 30

what is contractility

Answer 30

the force of contraction for a given fibre length

Question 31

was do extrinsic mechanisms do

Answer 31

increases contractility without increasing fibre length

Question 32

what happens to aortic pressure when peripheral resistance is increased

Answer 32

it increases

Question 33

what happens to the filling of the heart when peripheral resistance is increased

Answer 33

it decreases as venous pressure is reduced

Question 34

what is cardiac output

Answer 34

how much the ventricles empty

Question 35

what does cardiac output depend on

Answer 35

how hard the heart contract and how hard it is to eject blood

Question 36

what increases contractility

Answer 36

sympathetic drive (extrinsic mechanisms)

Question 37

what happens to the total peripheral pressure when metabolism increases

Answer 37

decreases to supply more blood. this causes an increase in venous pressure and decrease in arteriole pressure so the heart responds by pumping more

Question 38

what happens to the TPR when eating

Answer 38

decreases as there is vasodilation. this decreases arteriole pressure and increases venous pressure so heart rate increases

Question 39

what happens to venous pressure when you stand

Answer 39

it decreases so cardiac output decreases causing arteriole pressure to decrease

Question 40

true or false; pressure changes in the veins and arteries when standing up can be corrected by intrinsic mechanisms

Answer 40

false. baroreceptor reflex and the ANS increase heart rate and TPR. if this doesn't work you get postural hypotension