cardiac output

Question 1

what is afterload

Answer 1

the load the heart must eject blood against( roughly equivalent to aortic pressure)

Question 2

what is preload

Answer 2

amount the ventricles are stretched in diastole

Question 3

what is central venous pressure

Answer 3

pressure in large veins draining into the heart

if the pressure is high then heart will fill more and end diastolic vol will be greater

Question 4

what is total peripheral resistance (aka systemic vascular resistance )

Answer 4

resistance to blood flow offered by the systemic vasculature

Question 5

where is the greatest resistance in the vascular system and how does this affect pressure elsewhere

Answer 5

arterioles

causes pressure in capillaries and venous side to fall but pressure in arterial side to increase

Question 6

what happens if TPR falls and cardiac output is unchanged

Answer 6

arterial pressure decreases easier for blood to get to venous side.
venous pressure increases

Question 7

what are the effects of increasing total peripheral resistance

Answer 7

increase in arterial pressure

decrease in central venous pressure

Question 8

what are the effects of increasing cardiac output if TPR is unchanged

Answer 8

more blood is being pumped out so arterial pressure increases and central venous pressure decreases.

Question 9

what are the effects of decreasing CO and keeping TPR unchanged

Answer 9

less blood ejected so arterial pressure decreases and venous pressure increases.

Question 10

what happens when there is a higher demand for blood in tissues

Answer 10

arterioles and precapillary sphincters will dilate. Therefore TPR falls. The heart needs to pump more so that the arterial pressure doesn’t fall and the venous pressure doesn’t rise

Question 11

what is the relationship between intraventricular pressure and venous pressure

Answer 11

the higher the venues pressure the more the heart fills. the more the heart fills the higher the left ventricular pressure
displayed in ventricular compliance curve

Question 12

what is the Frank-starling Law of the heart

Answer 12

the more the heart fills the harder it contracts(up to a limit)
as its beings stretched more

Question 13

what happens in cardiac muscle when it stretches in relation to calcium sensitivity

Answer 13

calcium sensitivity increases which is why the length tension curve is steeper in cardiac muscle than skeletal muscle

Question 14

what is an intrinsic control mechanism on the heart

Answer 14

increased stroke vol with increased filling

same vol of blood pumped to body must also be pumped to lungs

Question 15

example of extrinsic factors on starling curve

Answer 15

sympathetic stimulation

circulating adrenaline

Question 16

what factors determine cardiac output

Answer 16

how much the ventricle empties- determined by how hard it contracts, how hard it is to eject blood
stroke vol, heart rate
contractility and heart rate are controlled by the autonomic nervous system.

Question 17

how arterial blood pressure affects nervous system

Answer 17

stretch receptors in aorta and carotid arteries sense arterial bp and alter parasmpathetic and sympathetic ns activity to control heart rate and contractility.
decrease in arterial bp reduces parasympathetic ns and stimulates sympathetic ns to increase heart rate and contractility

Question 18

what are the effects of increase in metabolism on TPR,CO,arterial pressure and venous pressure

Answer 18

TPR falls to supply more blood
results in a decrease of arterial pressure and increase in venous pressure
heart responds by pumping more

Question 19

how the cvs responds to eating a meal (local vasodilation of gut-needs blood supply)

Answer 19

TPR decreases, arterial pressure decreases
this is detected by stretch receptors in arteries stimulating increase in sympathetic NS increasing contractility which increases stroke vol & heart rate.
overall increasing cardiac output

Question 20

how standing up affects CNS

Answer 20

standing up causes pooling of blood in legs due to effect of gravity on a column of liquid.
venous pressure , cardiac output and arterial pressure decrease.
cannot be adjusted by intrinsic factors.
baroreceptor reflex and autonomic NS increase heart rate, contractility and increase TPR.
if these reflexes don’t work you get postural hypotension ( not enough blood going to brain causing dizziness and faint).

Question 21

why is there higher cardiac output during exercise

Answer 21

calf muscle pumping and venoconstriction(Smooth muscle cells in veins contract) returns more blood to the heart.
Decreased TPR increases venous return
increased contractility and heart rate due to increased sympathetic drive

Question 22

why is the internal jugular vein important

Answer 22

is in direct contact with superior vena cava which drains into right atrium. therefore changes in pressure in right atrium transmit back to the internal jugular vein.
biphasic pulse

Question 23

conditions that will increase jugular venous pressure

Answer 23

if right sided of heart doesn’t pump blood out properly
volume overload with IV infusion
if anything impairs filling of the heart e.g stabbing