about heart

[gustavson]

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Hi everybody,

I'm not sure if this would be the right place to ask a question, but I'll give it a try: given the pressures the heart operates at, why do we not feel it contracting? Seems interesting and I couldn't find an answer yet.

Thank you.

 

[thos]

A couple of thoughts off the top of my head.

1. Maybe it's like wearing clothes, after a few minutes you don't notice them anymore because your sensory system acclimates. Well, your heart is always beating.

2. Speaking of the sensory system, what's it like inside the chest anyway? Is it like the brain, which has no pain receptors to speak of? (This isn't rhetorical, I really don't know).

3. Sometimes I do notice my heart beating.

4. I'm not sure why the pressure is important. Do you mean because it's a strong contraction? Besides, what's the touchstone for a pressure we do notice vs. one we don't?

 

[xanthines]

The heart has quite a few pain receptors. Angina, anyone?

As near as I can tell, the baroreceptors do not send pain signals, they send a signal (if bp drops, that is) to your vasculature to "tighten up", and to your kidneys so save water both of which will elevate your blood pressure. Sorry if that's vague, but that's about all I can muster right now (cardio was so long ago!). In addition, when you get an infarct (ie "a coronary") and heart tissue begins to die, the cellular components bind to receptors in the heart which DO cause pain. I think they are A2 receptors or something and recognize adenosine.

-X

A couple of thoughts off the top of my head.

1. Maybe it's like wearing clothes, after a few minutes you don't notice them anymore because your sensory system acclimates. Well, your heart is always beating.

2. Speaking of the sensory system, what's it like inside the chest anyway? Is it like the brain, which has no pain receptors to speak of? (This isn't rhetorical, I really don't know).

3. Sometimes I do notice my heart beating.

4. I'm not sure why the pressure is important. Do you mean because it's a strong contraction? Besides, what's the touchstone for a pressure we do notice vs. one we don't?

 

[Gfunk6]

I think they are A2 receptors or something and recognize adenosine.

All correct, except for this minor bit. ATP degrades to adenosine during ischemia --> binds A1 receptors --> pain.

Re: the OP question, I agree w/ thos and xanthines. Baroreceptors don't transmit pain. Also when you stress your heart by exercise, fear, or whatever the contracting myocardium is so strong that it probably moves adjacent structures with afferent pain fibers which can result in the sensation of feeling your heart beating in your chest.

 

[thos]

The heart has quite a few pain receptors. Angina, anyone?

I'll pass on the angina, thanks anyway.

Good point, I guess I was really thinking more of non-pain sensory like pressure, proprioception, etc., the kind of things that would allow one to feel the movement of the heart (although I didn't make that very clear).

 

[xanthines]

Why? It's a lot fun!

Oh well, maybe next time...

-X

I'll pass on the angina, thanks anyway.