control of cardiac output

Question 1

define after load

Answer 1

load heart must eject blood against (aortic pressure)

Question 2

define preload

Answer 2

amount ventricles are stretched in diastole

Question 3

define TPR (total peripheral resistance)

Answer 3

resistance to blood flow offered by all systematic vascuculture

Question 4

what happens when you increase the resistance in the blood vessel

Answer 4

the greater the resistance the more pressure decreases on the venous side (after the pressure increase) and the more it increases on the atrial side (before pressure increase)

Question 5

in which vessel does pressure most decrease in the CVS

Answer 5

decreases most in the arterioles due to them offering the most resistance. largest decrease in size of lumen

Question 6

how decreasing TPR affects venous pressure, arterial pressure and cardiac output

Answer 6

arterial pressure decreases, venous pressure increases and cardiac output does not change

Question 7

how increasing TPR affects venous pressure, arterial pressure and cardiac output

Answer 7

arterial pressure increases, venous pressure decreases and cardiac output does not change

Question 8

what happens to arterial and venous pressure when you increase cardiac output

Answer 8

arterial pressure increases and venous pressure decreases because more blood pumped out of the venous system (TPR doesnt change)

Question 9

what happens to arterial and venous pressure when you decrease cardiac output

Answer 9

arterial presure decreases because less blood being pumped into venous system and venous pressure increases

Question 10

what happens when demand for blood in tissues increases

Answer 10

sphincters dilate and resistance falls. the heart therefore needs to pump more so arterial pressure doesnt fall and venous pressure doesnt rise. this is a response coordinated by intrinsic and extrinsic mechanisms

Question 11

equation for cardiac output

Answer 11

stroke volume (usually 70ml) x heart rate

Question 12

how to calculate stroke volume

Answer 12

end disatolic volume - end systolic volume

Question 13

how to increase stroke volume

Answer 13

increase EDV by filling ventricles more and decrease ESV by emptying ventricles more

Question 14

explain the ventricular compliance curve

Answer 14

shows that ventricular volume increases as ventricular pressure increases. this is because the heart fills more if there is a higher venous pressure and the therefore there is a higher ventricular pressure. DRAW GRAPH

Question 15

what is the frank starling law

Answer 15

if you stretch the fibre of the heart before contraction it will contract harder and therefore the heart fills more and it contracts harder. therefore increasing venous pressure increases contraction

Question 16

describe and draw the starling curve

Answer 16

increasing venous return leads to higher LVEDP and an increased stroke volume. shows sigmoidal curve with stroke volume down y axis and LVEDP across x axis

Question 17

describe and draw the length tension curve for cardiac muscle

Answer 17

if the sarcomere has too much overlap it interferes with contraction and also muscle is more sensitive to calcium if muscle fibres are stretched. is sigmoidal curve with contraction force down y and resisting sarcomere length across x axis

Question 18

why do the right and left sides of the heart both have same amounts of blood

Answer 18

explained by starlings law. its under intrinsic control if the stroke volume increases. if stroke volume increases more blood pumped to opposite side of the heart increasing its stroke volume too

Question 19

how contractility force is controlled by extrinsic factors

Answer 19

more sympathetic and adrenaline means increased contractility and therefore higher stroke volume and PVEDP and it decreases with less sympathetic stimulations

Question 20

how increased arterial pressure decreases stroke volume

Answer 20

aortic pressure increases when TPR increases. This decreases venous pressure and stroke volume goes down due to decreased filling of ventricles. overtime this causes hypertension and hypertrophy

Question 21

how CVS responds to eating a meal and vasodilation in the gut to supply extra blood supply to gut

Answer 21

TPR decreases due to vasodilation this decreases arterial which increases heart rate pressure and decreases venous pressure which increases stroke volume. both these increase cardiac output which decreases arterial pressure and increase venous pressure

Question 22

how CVS responds to standing up

Answer 22

blood pools in venous system when you stand up decreasing venous pressure and therefore cardiac output which in turn decreases arterial pressure. can’t adjust these consequences by intrinsic mechanisms.

Question 23

how CVS responds to exercise

Answer 23

vasocontriction and muscle pumping increases blood returning to heart. in response heart rate increase and TPR decreases to increase venous return. also contractility increased by sympathetic nervous system. all of these increase cardiac output

Question 24

what is the jugular venous pulse

Answer 24

it measures venous pressure and seen along neck muscle. its an important exam to evaluate cardiac contains because there are no valves in this vein. both a and v waves observed as pulses in the physical exam

Question 25

draw an explain the graph

Answer 25

a- atrial contraction increases pressure
x- atrial relaxation decreases pressure
c- eluding of tricuspid valve with ventricular contraction
x’- downaward movement of tricuspid valve with ventricular contraction decreases atrial pressure
v- pressure increases as atria fill
y - atrial emptying as tricuspid valve opens. pressure decreases

Question 26

what is an elevated JVP caused by

Answer 26

too much fluid from an IV infusion, obstruction of superior vena cava, inability to pump blood (bradycardia, right ventricular failure and more) and hyper dynamic circulation all cause an elevated JVP.