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22 Cards in this Set
- Front
- Back
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What is preload?? |
The initial stretching of the cardiac myocytes prior to contraction. It is directly related to end diastolic volume |
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What is afterload? |
The force that the heart must overcome in order to eject the blood. Otherwise known as total peripheral resistance |
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What is contractility? |
The intrinsic strength of the cardiac muscle to contract |
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Which components affecting stroke volume are intrinsically controlled? |
Preload and afterload |
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Which component of SV is extrinsically controlled? |
Contractility, controlled by autonomic nervous system |
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What effect does increased preload have on SV? |
Increases it |
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What effect does increased afterload have on SV? |
Decreases it |
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How can contractility be extrinsically controlled? |
Autonomic nerves and circulating hormones |
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How is the heart parasympathetically innervated? |
By the vagus nerve, CN X, arising from the medulla oblongata and innervating mainly supraventricular structures |
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How is the heart sympathetically innervated? |
Via C1, C2, C3, and C7, C8, T1, T2, T3, T4
Arising from sympathetic trunk and innervating supra, atrial and ventricular structures |
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What is the pre- disease state? |
A state where there are no overt clinical symptoms, but the cardiac innervation has begun to remodel itself in response to a pathological stimulus |
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What happens in the pre- disease state? |
Sympathetic nervous system becomes overactive Parasympathetic becomes underactive |
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Are cardiac myocytes innervated by varicosities or presynaptic terminals? |
Varicosities |
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What is Takotsubo cardiomyopathy? |
A sudden weakening of Muscular contraction after a physical or emotional stressor, such as divorce or bereavement. It is thought to be caused by an overstimulation by the sympathetic nervous system which leads to heart failure |
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What is Frank Starlings Law of the heart? |
The intrinsic relationship between EDV and SV |
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How does Frank Starlings Law relate EDV to SV? |
As EDV increases, it increases preload on the heart. This increases ventricular contraction which leads to an increase in SV. However, past a maximum point, increasing EDV will decrease SV |
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Why should you raise someone's legs if they have fainted? |
It will increase blood flowing back to the heart, raising CVP, RA pressure, preload, EDV, SV, and consequently CO |
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How does gravity and posture influence venous return? |
If you are standing up, blood pools around your feet and so venous return decreases |
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Draw the Frank-Starling curves |
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How does PKA affect intracellular Ca? |
It will phosphorylate cell membrane Ca channels which allow calcium to flow into the cell |
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Which is the more effective modulator of cardiac output? |
Heart rate |
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Why is ischaemia Negatively inotropic? Describe the mechanism |
Ischaemia causes an increase in lactic acid due to anaerobic respiration, which decreases pH of cell. Lower pH means more protons, which have a higher affinity for TnC than calcium. Protons act as competitive inhibitors of TnC, which decreases contractility |
