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Pathophysiology 2 > Cardiac centre > Flashcards

Cardiac centre Flashcards

1
Q

Cardiac centre

A

events associated with one heartbeat

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2
Q

cycle

A

In a normal cycle the atria contract while ventricles relax followed by atrial relaxation and ventricular contraction

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3
Q

Systole

A

contraction

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4
Q

Diastole

A

relaxation

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5
Q

Relaxation period

A

end of heartbeat chambers in diastole

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6
Q

isocolumetric relaxation

A

mitral and tricuspid valves closed no change in blood volume in ventricles

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7
Q

ventricular filling

A

ventricle diastyole
intraventicular pressure drops below atrial pressure
AV valve opens
passive ventricle filling

rapid ventricular filling
diastasis- only small colume enters
atrial systole pumps 20-25mls of blood

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8
Q

End-diastole volume

A

each ventricle contain 130mls
atrial systole 20-30% of EDV
Aortic and Pulmonary valves remain shut

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9
Q

Ventricular Stystole

A

near end of atrial systole ventricles depolarise and ventricular contraction begins
A-V valves are pushed closed by blood
after 0.05 seconds all valves are shut
isovolumetric contraction occurs
ventricular ejection occurs when pressure in ventricle opens Ao and pulmonary valve

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10
Q

t wave

A

ventricular polarasation

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11
Q

Cardiac Output

A

CO = SV x HR
ml per min

the total amount of blood ejected from the left ventricle in one minute

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12
Q

Cardiac reserve

A

Cardiac reserve refers to the difference between the rate at which the heart pumps blood and its maximum capacity for pumping blood at any given time

cardiac reserve is 4-5x than at rest

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13
Q

Age related changes

A

decreased maximal CO
changes in nodal and conducting cells
decreased elasticity of fibrous skeleton

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14
Q

Stroke volume factor

A

preload
contractility
afterload

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15
Q

Preload

A

greater preload on cardiac muscles fibers prior to contraction increases their force of contraction

if HR > 160 bpm SV falls due to reduced filling time
low heart rate have longer filling times raising preload giving larger stroke volumes

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16
Q

Starlings law of the heart

A

The more the heart is filled in diastole, the greater the stretch and the greater the force of systole

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17
Q

Contractility

A

the strength of contraction at a given preload

18
Q

positive inotropic substances

A

calcium

adrenaine

19
Q

negative inotrophic substances

A

beat blockers

calcium channel blockers

20
Q

Afterload

A

the pressure in the aorta and pulmonary artery that needs to be exceeded
increased after load result in reduced SV
more blood remainsin ventricle at end of systole

21
Q

preload

A

volume of blood im ventricles at end of diastole

increased
-hypervolemia
regurgataion of cardiac valves
heart failure

22
Q

Afterloas

A

resistance left ventricle must overcome to circulate blood

  • increase
  • hypertension
  • vasoconstriction

higher after load = higher cardiac workload

23
Q

regulation of HR

A

autonomic control

sympathetic and parasympathetic

24
Q

sympathetic

A

sympathetic nerve increases the HR and strength of contraction

25
Q

parasympathetic

A

parasympathetic nerve slows HR

26
Q

Input to cardiovascular centre

A

cerebral cortex
limbic system
hypothalamus

proprio-receptors
chemo-receptor
baro-receptors

27
Q

output to heart (sympatheitc)

A

cardiac accelerator nerve

increased rate of spontaneous depolarization of SA node and AV node increasing HR

Increased contractility of atria and ventricles increasing stroke volume

28
Q

output to heart (parasympatheitc)

A

Vagus nerves (cranial nerve X)

decreased rate of spontaneous depolarization in SA node and AV node decreasing HR

29
Q

Chemical regulaiton hormones

A

adrenal medulla produces adrenaline and noradrenalince

thyroid hormones

increases HR and contractility

30
Q

chemical regulation IONS

A

increased potassium and sodium decrease HR and contractility
increased calcium increases HR and contractility

31
Q

Phases

A 
Atrial contraction
isovolumetric contraction
rapid ejection
reduced ejection
isovolumetric relaxation
rapid filling
reduced filling
32
Q

atrial systole

A

P wave of the EGC
electrical depolarization of the atria

atria contract
atrial pressure increases
blood flows through AV valve
Aortic + Pulmonary valves remain shut so no blood leaves ventricles
Delay before qrs complex because allow ventricles to fill before contracting
rapid blood flow into ventricles

(1/3 of filling time), pumps 20-25 mls of blood, each ventricle contains about 130ml (EDV) pumps 20-30% of EDV.

33
Q

End diastole volume

A

after atrial contraction atrial pressure falls
pressure gradient across AV valve
AV valve closes
ventricular volumes are maximal-EDV

34
Q

Preload

A

left ventricle end diastole volume

120ml

35
Q

Isovolumetic contraction

A

QRS complex of the the ECG

ventricular depolirisation
excition-contraction coupling myocyte contraction
rapid increase in intraventricular pressure

AV valve closes when intraventricular pressure exceeds atrial pressure

contraction of ventricles increases pressure with no change in volume as semilunar valves are closed

36
Q

Rapid ejection

A

interventricular pressie exceed the pressures within the aorta and pulmonary artery
aortic valves and pumonic valve open
blood ejected due to pressure gradient between ventricles and arteries

37
Q

Reduced ejection

A

T- wave of ecg

ventricular repolarization
ventricle emptying falls

38
Q

isovolumetric relaxation

A

all valves closed

intraventricular pressures fall aortic and pulmonic valve close

39
Q

rapid filling

A

ventricles relax intraventricular pressure falls below atrial pressure
AV valves rapidly open
passive ventricular filling

intraventricular pressure continues to fall as ventricles relaxation occurs

40
Q

reduced filling

A

ventricle fill with blood
increase intraventricular pressure
decreased pressure gradient
90% of ventricle filling is passive

41
Q

Cardiac cycle

A
  • all chambers in diastole at end of heartbeat,. The pressure in the ventricles falls and therefore Aortic and Pulmonary valves close
  • Isovolumetric relaxation - Mitral & tricuspid closed, no change in blood volume in ventricles. The ventricles continue to relax & pressure falls.
  • rapid ventricular filling (1/3 of filling time) AV (Mitral & tricuspid) valves open. Blood pours from atria into the ventricles passively.
  • Atrial Diastasis only small volume enters
  • Atrial systole resembles P wave (final 1/3 of time), pumps 20-25 mls of blood, each ventricle contains about 130ml (EDV) pumps 20-30% of EDV. Aortic + Pulmonary valves remain shut so no blood leaves ventricles Delay before qrs complex because allow ventricles to fill before contracting
  • Ventricular contraction QRS wave
  • Ventricular systole - near end of atrial systole ventricles depolarise and ventricular contraction begins, A-V valves are pushed closed by blood All valves are now closed (0.05 secs)
  • Isovolumetric contraction occurs, contraction of ventricles increases pressure with s semilunar valves are closed therefore pressure in ventricles rises
  • Ventricular ejection interventricular pressure exceed the pressures within the aorta and pulmonary artery opening Aortic and Pulmonary valves , lasts 0.25 secs valves close, relaxation begins again
  • T wave resemble ventricular repolarisation, QRS complex cover atrial repolarisation
42
Q

3 factors that govern cardiac output

A

Preload- (end diastolic volume) i that is amount of blood returning to left ventricle i.e. venous return. Greater venous return greater CO. Starlings law of heart s the amount of strectch of the left ventricle at the end of diatole prior to contraction related to muscle sarcomere length.

Afterload- pressure in the ascending aorta that has to overcome to open aortic valve and eject blood.

Contracility- the force of contraction at a given preload

Pathophysiology 2 (18 decks)

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