17-4: Cardiac output

Question 1

cardiac output

Answer 1

the amount of blood ejected from each ventricle in one minute, determined by heart rate and stroke volume

Question 2

heart rate

Answer 2

the number of heartbeats per minute

Question 3

stroke volume

Answer 3

amount of blood ejected by a ventricle during each beat

Question 4

What is the cardiac output equation?

Answer 4

CO = SV x HR

Question 5

cardiac reserve

Answer 5

the difference between max CO and resting CO

Question 6

What factors affect stroke volume?

Answer 6

amounts of blood in the ventricles - end diastolic volume and end systolic volume

Question 7

end diastolic volume

Answer 7

the volume of blood entering each ventricle during diastole (eg. when ventricles are full and ready to contract)

Question 8

EDV is determined by the ___

Answer 8

length of diastole

Question 9

If HR increases, EDV ___; if HR decreases, EDV ___.

Answer 9

HR increase: EDV decreases (since diastole is shorter)

HR decreases: EDV increases

Question 10

end systolic volume

Answer 10

volume of blood remaining in ventricle after systole (eg. after contraction has finished)

Question 11

What is the equation for ESV?

Answer 11

ESV = EDV - SV

or:
SV = EDV - ESV
(volume of blood entering ventricle during diastole - volume of blood remaining in ventricle after systole)

Question 12

What is ESV determined by?

Answer 12

arterial blood pressure: high BP in the arteries leaving the heart prevents the ventricles from emptying normally (pushing against pressure in the SL valves)

Question 13

If blood pressure increases, ESV ___ and SV ___

Answer 13

ESV increases and SV decreases

Question 14

afterload

Answer 14

back pressure exerted on SL valves by blood in arteries leaving heart; this pressure must be overcome for blood to be ejected from ventricles

Question 15

Starling’s Law of the Heart

Answer 15

the more you stretch the myocardium (due to blood in chambers), the harder it will contract, maintaining cardiac output

Question 16

preload

Answer 16

amount the ventricles are stretched by the blood they contain just before contracting; critical factor controlling stroke volume and depends on EDV

Question 17

venous return

Answer 17

amount of blood returning to the heart

Question 18

Increased venus return causes ___ stroke volume

Answer 18

increased (increases the stretch per Starling’s law)

Question 19

A greater preload ___ the force of contraction, ensuring the R&L ventricles will pump ___.

Answer 19

increases; equal volumes of blood, preventing backup of blood in the circulation