cardiac output (lecture 4 )

Question 1

what is cardiac output

Answer 1

volume of blood ejected by each ventricle each minute

Question 2

what is venous return

Answer 2

volume of blood returning to atrium each minute
NB: must be equivalent to Cardiac Output

Question 3

what factors influence cardiac output

Answer 3

metabolism
rest
exercise
age
bpdy size

Question 4

what is the formula for cardiac output

Answer 4

heart rate x stroke volume

Question 5

what is stroke volume

Answer 5

volume of blood ejected by each ventricle per heart beat

Question 6

what is the parasympathetic control of cardiac output

Answer 6

vagus via nucleus ambiguus

Question 7

what is the sympathetic control of cardiac output

Answer 7

via rostral ventrolateral medulla
sympathetic chain

Question 8

what are the major factors that effect stroke volume

Answer 8

Preload (intrinsic mechanism)
Contractility (extrinsic and intrinsic influences)
Afterload (extrinsic mechanism)

Question 9

what is frank starlings law

Answer 9

increased preload (EDV), increases contractility, increases SV

Question 10

what is preload

Answer 10

the degree of stretch of the heart muscle fibers at the end of diastole

depends on the end diastolic pressure P, chamber radius r and wall thickness w

Question 11

what are Positive inotropic agents

Answer 11

factors that increase contractility: sympathetic neurotransmitters noradrenaline, circulating adrenaline and reduced beat interval

Question 12

what are Negative inotropes

Answer 12

factors that decrease contracility: ischemia, acidosis, heart failure, anaesthetics, parasympathetic fibre activity and calcium channel blockers

Question 13

what is ventricular afterload

Answer 13

the resistance the heart must overcome to eject blood. It’s mainly determined by arterial blood pressure and vascular resistance.