Hearts

Heart shapes can be found in nature, if you’re lucky enough to see one.  There’s a heart on this elephant’s trunk, a ridge of skin that feels like fine shoe leather.  One of his wrinkles pierces the lower third of this heart shape, from left to right, straight as an arrow.  His real heart hangs between his breastbone and ribs, a little to the left, just like mine does.  But instead of having a heart with a single point, an elephant’s heart has two points at its apex – so it’s the wrinkled outline of a human heart that he carries on his trunk.

 

The human heart is approximately five inches long, three-and-a-half inches wide and shaped like a pulsing cone.  It is the only muscle in my body that acts on its own – my heartbeat doesn’t need any messages from my brain.  The cells in my heart tissue involuntarily constrict, all together, all at once, over and over, a soft perpetual-motion machine.  Rip my heart from my body, chop it into pieces, immerse the pieces in a saline solution, and then give them a small jolt of electricity.  The remnants of my cardiac muscle will contract . . . contract . . .  contract – all on their own, sometimes for hours.

It’s designed to be strong, our hearts.

 

 

4 responses

  1. Eye lids, intestines, and a few other muscles also act “on their own” ie, are part of the “involuntary nervous system” — and ALL muscles will contract via electrical impulse, even if removed from the body and immediately put into a 10% salinesolution.

    1. Thanks for this info, Meg. Will any other of the voluntary muscles keep on contracting when jolted with electricity in a saline solution? It’s my understanding only heart cells will do so, but I want to be correct with what I write! Not being a scientist….I’m using this image in my book about elephants and want to make sure about it. Any help is greatly appreciated if you know more. Thanks!

      1. I used to be an histologist, long, long ago. It makes it a bit hard to answer succinctly. How big is the sample? If you’re talking about a contiguous chunk, than most smooth muscles will contract for 1-2 minutes in saline, if stimulated by electrical current, while the heart muscle will “beat” for 5-10 minutes providing you’re dealing with the entire heart, and the heart is undamaged. A few cells are just like any other smooth muscle tissue. This is, as far as I know, true of all mammals. I think you’re thinking of dissecting frogs in High School Biology, where one can keep a frog’s heart beating almost as long as one wants, as long as there’s saline and electrical current. I’ve read that there are (now) ways to keep a mammal’s heart cells actually growing, but it’s not just saline and electricity, and I haven’t seen it in any journal I truly trust.

      2. Once again, thanks so much. I’m dealing with a chapter right now that includes this, so I’ll need to rewrite it a bit. Histologist must look cool on your resume! I avoided biology just because of frogs and took physics instead . . . Funny how life cycles round to the subjects you always wanted to avoid….

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