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Pumps Pipes and Electrics > Lecture 6 - cardiovascular response to stress > Flashcards

Lecture 6 - cardiovascular response to stress Flashcards

1
Q

What external factors affect CO?

A 
ANS
noradrenaline / adrenaline 
drugs
electrolytes
excercise
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2
Q

How is CO measured?

A

HR x SV

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3
Q

What is SV?

A

EDV - ESV

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4
Q

typical values for SV/EDV/ESV

A

SV = 70
EDV=140
ESV=70

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5
Q

What factors affect HR?

A
  • autonomic innervation
  • hormones
  • fitness levels
  • age
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6
Q

What factors affect SV?

A
  • heart size
  • fitness levels
  • gender
  • contractility
  • duration of contraction
  • Preload
  • afterload
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7
Q

How is heart rate maintained?

A

SAN intrinsic rate of 110bpm

PNS lowers the rate to 60-80

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8
Q

what are factors that change the HR?

A

chronotropic agents?

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9
Q

What are positive chronotrophic factors?

A
  • SNS
  • excercise
  • increased body temperature
  • hypercalaemia
  • hypokalaemia
  • hyponatraemia
  • chemorceptors –> acidotic
  • atropine/caffeine
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10
Q

What factors are negative chronotrophic?

A
  • PNS–> AcH
  • hypocalaemia
  • hyperkalaemia
  • hypernataemia
  • alkali state
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11
Q

How does HR increase during excercise?

A

exercise stimulate proprioceptors in vessels and increases body temperature

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12
Q

What is HR max

A

The maximum rate the heart can reach without affecting the filling of the ventricles

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13
Q

why is there a limit to rapid filling time?

A

excessive increase in HR affects CO

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14
Q

what is preload

A

Volume of blood entering the ventricles

-Preload= the degree of stretch on myocardium when filled with blood at end of diastole (EDV)

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15
Q

What is afterload

A

resistance the ventricles have to overcome to pump blood out the ventricles

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16
Q

What is contractility ?

A

contraction of the myocardium

17
Q

What is the preload increased in?

A

hypervolaemia
regurg of cardiac valves
heart failure

18
Q

What is afterload increased in?

A

HTN

vasoconstriction

19
Q

What happens when afterload increases?

A

CO increases

20
Q

What does a higher preload mean

A

Higher EDV

21
Q

What factors reduce preload

A

myocardium damage –> reduced stretch

Increased HR –> reduced filling time

22
Q

What factors ensure blood returns to the heart

A
  • gravity when standing -ve
  • skeletal muscle pump +ve
  • A-T pump when breathing +ve
23
Q

Impact of IV fluids on blood volume?

A

Bainbridge reflex

  • receptors in the right atrium detect distension
  • sympathetic activity stimulate through SAN
  • HR increases
24
Q

impact of IV fluids on BP in atrium?

A

Baroreceptor reflex

  • pressure increase detected by baroreceptors in atria#
  • signals to decrease HR
  • increased urine output –> decreased vasopressin and increased ANP
25
Q

What does the overall effect of the baroreceptor and bainbridge reflex depend on?

A

the previous HR

26
Q

Explain how ANP works?

A
  • secreted by the heart
  • in response to atrial stretch
  • causes glomerular arteriolar dilation
  • diuresis
27
Q

explain how RAAS works?

A
  • regulates pressure + volume
  • decrease in GFR –> kidney releases renin
  • renin cleaves AT-1 into AT-2
  • AT-2 is a potent vasoconstrictor –> increases BP
28
Q

What does an increase in afterload do to SV?

A

decreases SV

29
Q

what factors increase afterload?

A
  • HTN
  • cartoid artery stenosis
  • atherosclerosis
  • carotid valve stenosis
  • pulmonary hypertension
30
Q

What does an increased afterload lead to?

A

LVH

31
Q

What is SCD?

A
  • inherited heart condition
  • heart muscle thickens and becomes stiff
  • most common genetic heart condition 1 in 500 affected
  • AD
32
Q

How is contractility affected in pathology?

A

Acidoisis (poorly: diabetes, heart attack, sepsis) – reduced contractility
H+ is the strongest –ve ionotrope
Ionotropes for cardiogenic shock
+ve: Digoxin, Ad, NorAd, Dopamine, Dobutamine
-ve: β blockers, Diltiazem

33
Q

What is the frank-starling law?

A

The Frank–Starling law of the heart represents the relationship between stroke volume and end diastolic pressure. The law states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction, when all other factors remain constant

34
Q

What does the frank-starling graph represent

A

relationship between cardiac output and EDV

35
Q

What does a steep curve on a frank-starling graph represent?

A

increased contractility

-

36
Q

What does a less steep frank-starling curve show?

A

reduced contractility

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