cardiodynamics

Question 1

definition of cardiodynamics

Answer 1

cardiodynamics is the study of blood flow i.e the cardiac output
blood flow is required for the flow of organ perfusion and for the delivery of oxygen and removal of co2 from tissues

Question 2

flow equation

Answer 2

change in pressure/resistance

Question 3

how do you calculate change in pressure

Answer 3

mean arterial pressure- right arterial pressure

Question 4

cardiac output definition

Answer 4

stroke volume xheart rate

Question 5

blood pressure equation

Answer 5

blood pressure= cardiac outputx total peripheral resistance

Question 6

if the pressure stays the same what does decreasing resistance do to the flow

Answer 6

increase the flow

Question 7

if sepsis causes vasodilation how does this reduce blood flow instead of improving it

Answer 7

reduces afterload
reduced venous return
reduced preload-dilation of venules
hypovolaemia- vasodilation causes permeable leaky capillaries
causes myocardial depression- affects contractility

Question 8

how is cardiac output controlled intrinsically

Answer 8

determined by the degree of stretch in myocardial fibres

Question 9

how is cardiac output controlled extrinsically

Answer 9

determined by the activity of autonomic nervous system and circulating hormones

Question 10

what three factors can affect cardiac output by affecting heart rate and stroke volume

Answer 10

preload
afterload
contractility

Question 11

what is preload

Answer 11

stretch of the heart muscle at the end of diastole determined by end diastolic volume and venous return

Question 11

what is afterload

Answer 11

resistance heart must overcome to eject blood during systole its determined by systemic vascular resistance and aortic pressure

Question 12

what is meant by contractility

Answer 12

strength of myocardial contractions independent of afterload and preload

Question 13

how does increasing preload increase cardiac output

Answer 13

frank starling law increasing preload enhances stroke volume because a greater volume of blood stretches the ventricular walls, optimising overlap of actin and myosin filaments in the heart muscle for a more forceful contraction
increased preload increases stroke volume which increases cardiac output

Question 14

how does enhances contractility increase cardiac output

Answer 14

increases ejection fraction (volume of blood pumped out of left ventricle with each beat) which boosts stroke volume
sympathetic nervous system activation adrenaline and noreadrenaline
positive ionotrophic agents digoxin dobutamine
increased contractility increases stroke volume so increased cardiac output

Question 15

how does reducing afterload increase cardiac output

Answer 15

reduces workload on the heart as less resistance that ventricle pumping needs to overcome making it easier for the ventricles to eject blood
lower afterload leads to increased stroke volume increasing cardiac output
ace inhibitors and nitrates can reduce afterload

Question 16

heart rate will increase cardiac output up until a certain point why

Answer 16

very high heart rate will reduce ventricular filling because diastole is shortened as very high heart rate reduces stroke volume

Question 17

what happens during exercise to the cardiac output

Answer 17

during exercise the cardiac output increases and is mostly contributed to by an increase in heart rate there is a slight increase in stroke volume of the heart this is due to vasodilation of the peripheral circulation and therefore a decrease in resistance to the cardiac contractions therefore a slightly higher pulse pressure. there is also an increase in stroke volume related to the the increased venous return and starlings force. increased muscle activity drives increased venous return. increased respiratory effort therefore pumping more return to the left side. increased sympathetic activity will increase contractility

Question 18

if the heart rate is too fast how do we slow it down

Answer 18

drugs
dc cardiovert shock with electricity
parasympathetic stimuli