The heart as a pump

Question 1

waves on ECG

Answer 1

created by excitation and recovery of different regions of the heart
height reflects amount of muscle involved

Question 2

P wave

Answer 2

atrial excitation

Question 3

QRS complex

Answer 3

ventricular excitation

Question 4

T wave

Answer 4

ventricular recovery

Question 5

interval/segment

Answer 5

interval includes the peaks
segment doesn’t

Question 6

isometric

Answer 6

contraction gives increase in tension in elastic elements first without a shortening of the muscle length
occurs if the load is too heavy to move

Question 7

isotonic

Answer 7

when muscle tension is high enough to match the load then can move the load
muscle shortens without a further increase in tension

Question 8

passive ventricular filling

Answer 8

pressure in ventricles falls lower than in the atria
AV (mitral and tricuspid) valves open
ventricles passively fill with blood

Question 9

atrial ejection

Answer 9

following P wave, atria contract
another 30% blood is pushed into the ventricles
attic and pulmonary (semilunar) valves closed as pressure higher in arteries than the ventricles

Question 10

isovolumic ventricular construction

Answer 10

following QRS ventricles start to contract
tension in muscle building (no shortening yet)
pressure higher in the ventricles than the atria
AV valves slam shut (lub)
pressure not yet high enough to open aortic and pulmonary valves

Question 11

ventricular ejection

Answer 11

pressure in ventricles now higher than arteries
aortic and pulmonary valves open (AV valves still closed)
ejection phase

Question 12

isovolumetric ventricular relaxation

Answer 12

following T wave ventricles start to relax
pressure falls lower in the ventricles than the arteries
aortic and pulmonary valves slam shut (dub)
ventricular pressure still higher than atria so AV valves still shut

Question 13

pre-load in length tension relationship

Answer 13

left ventricle preload is left ventricular end-diastolic finer length
preload is the resting length from which the muscle contracts

Question 14

afterload in length tension relationship

Answer 14

for the left ventricle is aortic pressure

Question 15

Frank-starling relationship

Answer 15

states the volume of blood ejected by the ventricle depends on the volume present in the ventricle at the end of diastole

cardiac output= venous return

Question 16

stroke volume

Answer 16

volume of blood ejected by the ventricle on each beat

Question 17

ejection fraction

Answer 17

fraction of the EDV ejected in one stroke volume

Question 18

cardiac output

Answer 18

total volume ejected by the ventricle per unit time

Question 19

stroke volume calculation

Answer 19

EDV- ESV

volume of blood in ventricle before ejection - volume remaining in the ventricle after ejection (end-systolic volume)

Question 20

approximate stroke volume

Answer 20

70l

Question 21

factors affecting stroke volume

Answer 21

preload
contractility
afterload

Question 22

how does preload affect stroke volume

Answer 22

changes in stroke volume occur following changes in resting ventricular muscle fibre length
mechanism intrinsic to the heart

Question 23

how does contractility affect stroke volume

Answer 23

inotropic effect
changes in stroke volume without changes in resting ventricular muscle fibre length (no change in preload)
mechanism extrinsic to the heart

Question 24

how does after load affect the heart

Answer 24

changes in aortic pressure

Question 25

postive inotropic effect

Answer 25

sympathetic nervous system
catecholamines
increased calcium ion availability (digoxin)

Question 26

negative inotropic effect

Answer 26

beta blockers
calcium ion channel blockers

Question 27

haemorrhage

Answer 27

reduced venous return
reduced EDV
reduced SV
sympathetic response, positive inotropic
CO= HR x SV
reduced filling time with large tachycardia (reduced EDV)

Question 28

sympathetic effects on force of contraction and relaxation

Answer 28

non/adrenaline binds to beta adrenoreceptors
phosphorylation of Ca channels, increased Ca influx and stronger force of contraction, more cross bridge cycling
relaxation is quickened by increased Ca pumped back into SR, pump works faster and reduces cytosolic Ca
increased amounts of Ca are stored in SR for next release
next beat can happen sooner and will be stronger

Question 29

how to calculate ejection fraction

Answer 29

stroke value divided by EDV

Question 30

ejection fraction

Answer 30

used to determine the effectiveness of the ventricles in ejecting blood
normally 55%
is an indicator of contractility

Question 31

how is ejection fraction of contractility

Answer 31

increase in ejection fraction reflects an increase in contractility

Question 32

cardiac output

Answer 32

depends on the volume ejected on a single beat and number of beats per minute
approximately 5000l/min in 70kg person

Question 33

what is the image and label the numbers

Answer 33

ventricular pressure-volume loops
1. atrial systole
2. isovolumic ventricular contraction
3. rapid ventricular contraction
4. reduced ventricular ejection
5. isovolumic ventricular ejection
6. rapid ventricular filling
7. reduced ventricular filling

A. mitral valve closing
B. aortic valve opening
C. aortic valve closing
D. mitral valve opening

Question 34

what does the image show

Answer 34

increased preload

Question 35

what does the image show

Answer 35

increased afterlaod