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health advisory Hospital Doctor Yu 2007-11-8 19:08:53

I want to know why there is pain when the cardiac muscle is deprived of oxygen? Are there sensory receptors that signal to the Central Nervous System that O2 is low?

Thanks a lot,

Mario

Answers:

There are pain receptors in the heart, and cell injury (ischemia) sets off those receptors.

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Hi. The pain is caused because the muscle is dying. There is sometimes no pain and that's called a "silent" heart attack, or MI.

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ischaemia is nothing but death of a tissue or muscle, related to loss of oxygen which can be related to blockage as a result of a tight band, or blockage caused by cholesterol, or blood clot.

the pain is because of the pressure caused by any of the above itiology on a pain nerve, that transmits messages to the pain center and received by the specific receptors of the heart for pain sensation

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The pain comes from a hypoxic state (lack of oxygenation) cells start dying. The vessels within the heart vasopres (or contract) causing pain. If I remember correctly from my college days its the chemo and baro receptors that trigger certain cascades especially to the nervous system regulating internal oxygen levels. It's a complicated event because respiratory acidosis, alkalosis, can occur and that's a weeks worth of lectures alone. PS ischemia just means tissue death usually from extensive trauma and lack of oxygen.

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There are sensory receptors in the heart but they are called "visceral afferents". You have these in other places of your body like intestines, kidneys etc. Evolutionarily you don't want to feel any pain in these organs because you can't do anything about it. Evolution did not know about surgery. If you felt pain everytime you ran from a predator because your oxygen got low, you would probably get eaten.