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Case 4 > cardiovascular physiology > Flashcards

cardiovascular physiology Flashcards

1
Q

what is stroke volume?

A

volume of blood pumped by one ventricle per contraction
~ 75ml

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2
Q

what is cardiac output?

A

volume pumped per ventricle per minute
~ 5L/min

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3
Q

what is venous return?

A

volume of blood returning to the heart

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4
Q

correlation between CO and VR?

A

should be equal

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5
Q

where does electrical activity originate in the heart?

A

sinoatrial SA node

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6
Q

how does the electrical activity spread?

A

via gap junction

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7
Q

role of annulus fibrosis?

A

non-conducting layer between atria and ventricles electrically insulates/isolates chambers

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8
Q

what does the P wave show?

A

atrial depolarisation

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9
Q

what is the Q interval?

A

P-R
interval between start of excitation of atria and ventricles

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9
Q

what is the QRS complex?

A

ventricular depolarisation
atrial repolarisation occurs but is obscured

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9
Q

what is the ST segment?

A

all ventricular tissue depolarised, contraction

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9
Q

what is the QT interval?

A

contraction occurring but includes ventricular repolarisation

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10
Q

what is the T wave?

A

ventricular repolarisation

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11
Q

how does activation of sympathetic nerves effect heart rate?

A
  • release of noradrenaline, binds to B1 receptors
  • increased opening of HCN channels
  • opens Ca2+ channels
  • increased phase 4 slope
  • increased heart rate
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12
Q

how does activation of parasympathetic nerves effect heart rate?

A
  • release of Ach, binds to muscarinic receptors
  • decreased opening of HCN channels
  • slowed opening of Ca2+ channels
  • opens additional K+ channels
  • reduces slope of phase 4
  • heart rate decreases
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13
Q

normal value for intrinsic rate of firing of SA node?

A

~ 100-110 APs per min

14
Q

what is preload ?

A

degree of stretch in ventricles due to end diastolic pressure

15
Q

what is the heterometric (intrinsic) mechanism of regulating force of contraction?

A

starlings law of the heart
- force of contraction is proportional to the INITIAL fibre length in diastole / number of cross bridges possible

16
Q

effect on muscles of low preload (almost empty chamber)?

A
  • actin and myosin overlap isn’t optimal
  • reduced ability to contract
17
Q

effect on muscles of high preload (full ventricle)?

A

stretching of muscle
optimal cross bridges available
increased affinity of troponin C to Ca2+
maximal force

18
Q

effect on muscles of heart failure(overfull heart)?

A

actin and myosin physically separated
prevents interaction
reduced force

19
Q

effects of sympathetic nerve stimulation on homeometric (extrinsic) mechanism?

A

increased stroke volume without change in initial fibre length
increased contractility (positive ionotropic)

20
Q

effect of catecholamines in extrinsic mechanism?

A

produces more forceful but shorter contraction

Case 4 (6 decks)

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