The heart as a pump Flashcards

1
Q

waves on ECG

A

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

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2
Q

P wave

A

atrial excitation

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3
Q

QRS complex

A

ventricular excitation

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4
Q

T wave

A

ventricular recovery

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5
Q

interval/segment

A

interval includes the peaks
segment doesn’t

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6
Q

isometric

A

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

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7
Q

isotonic

A

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

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8
Q

passive ventricular filling

A

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

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9
Q

atrial ejection

A

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

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10
Q

isovolumic ventricular construction

A

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

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11
Q

ventricular ejection

A

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

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12
Q

isovolumetric ventricular relaxation

A

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

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13
Q

pre-load in length tension relationship

A

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

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14
Q

afterload in length tension relationship

A

for the left ventricle is aortic pressure

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15
Q

Frank-starling relationship

A

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

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16
Q

stroke volume

A

volume of blood ejected by the ventricle on each beat

17
Q

ejection fraction

A

fraction of the EDV ejected in one stroke volume

18
Q

cardiac output

A

total volume ejected by the ventricle per unit time

19
Q

stroke volume calculation

A

EDV- ESV

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

20
Q

approximate stroke volume

A

70l

21
Q

factors affecting stroke volume

A

preload
contractility
afterload

22
Q

how does preload affect stroke volume

A

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

23
Q

how does contractility affect stroke volume

A

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

24
Q

how does after load affect the heart

A

changes in aortic pressure

25
Q

postive inotropic effect

A

sympathetic nervous system
catecholamines
increased calcium ion availability (digoxin)

26
Q

negative inotropic effect

A

beta blockers
calcium ion channel blockers

27
Q

haemorrhage

A

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

28
Q

sympathetic effects on force of contraction and relaxation

A

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

29
Q

how to calculate ejection fraction

A

stroke value divided by EDV

30
Q

ejection fraction

A

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

31
Q

how is ejection fraction of contractility

A

increase in ejection fraction reflects an increase in contractility

32
Q

cardiac output

A

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

33
Q

what is the image and label the numbers

A

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

34
Q

what does the image show

A

increased preload

35
Q

what does the image show

A

increased afterlaod