3 fascinating peculiarities of the heart and a great disadvantage

You’ve probably felt them: those muscle aches that you didn’t even know you had, and that appear after exercising.

The muscles in our legs and arms and even our face—called skeletal muscles—allow us to run, jump, and lift because at the subcellular level, these tiny protein strands collectively slide past each other causing the entire muscle to contract or lengthen.

And if we try harder than usual, we do a little damage.

That’s why a couple of days later we can’t walk downstairs without wincing. That pain is our cells repairing the damage. And by doing so, the muscles get stronger.

But have you ever wondered why, being a muscle and having been involved in the same activity, your heart doesn’t hurt?

What’s so special about the heart?

The answer, in a word, is: a lot, and here we will highlight a little.

Let’s start at the beginning… literally.

1. Always beating

The heart is the first structure to form in the uterus

“At first it’s basically a tube,” cardiologist Rohin Francis tells the BBC.

“That tube, through a really amazing sort of origami folding process, eventually becomes the mature heart.”

From very early in our embryological development, there is a primitive heart, which begins to beat.

Gradually, as we develop in the womb, it becomes more complex and eventually forms the four-chamber structure with which we are familiar.

So almost from the moment of inception to death, it is always beating.

That is why so early in pregnancy you can hear that heartbeat that moves parents so much.

And that’s not the only amazing thing, says the cardiologist.

“If you put a culture of cardiac cells in a Petri dish, even if it’s just a few, not only will they begin to beat spontaneously but they will also synchronize with each other.

“They just have an intrinsic tendency to throb.”

To do so, they need a lot of energy.

2. Super energetic

“Compared to those in skeletal muscles, cardiac cells are much more efficient,” explains Francis.

“They have a denser supply of mitochondria, so they are extremely energetic cells.”

Mitochondria are like the powerhouse of the cell.

“They create ATP that we use to fuel all of our cellular metabolism.”

Adenosine triphosphate (ATP) is an organic and hydrotropic compound found in all known life forms. It provides energy to drive many processes in living cells.

And energy is what it takes to move any muscle, particularly the heart which, even in a state of rest, is always working very hard.

Cells have to be able to keep beating steadily without becoming fatigued, and for that they need much higher levels of ATP than skeletal muscles.

But there is something that they have less of.

3. Few nerves

“When you’re talking about the sensation of pain in the skin or muscles, it’s very important to be able to pinpoint exactly where the pain is coming from, so you have a high density of sensory nerves supplying those parts of the body so you can pinpoint exactly where it’s coming from. the problem,” explains the cardiologist.

If it’s your internal organs, he adds, while it’s important for the organs to be able to tell the brain that something’s wrong, the information isn’t as precise.

“The sensory nerve density is much lower.”

It sounds worrying, but it would probably be more so if it were different because if it weren’t for the fact that we have far fewer nerve endings in our hearts, we would feel it constantly and we would be aware of every heartbeat… can you imagine?

But as wonderful as the heart is, it has one big drawback.

4. If it breaks, it can’t be fixed.

“The heart is terrible at repairing itself,” Sanjay Sinha, a senior fellow at the British Heart Foundation and professor of Cardiovascular Regenerative Medicine at the University of Cambridge, tells the BBC.

“When the average person has a heart attack or injury, what usually happens is that part of the heart muscle dies, and it never recovers.”

“It repairs itself to the extent that it forms a scar. But that muscle that you’ve lost won’t come back, so the heart doesn’t contract as well. That’s basically why it’s so serious.”

What is it about heart muscle tissue that doesn’t allow it to repair itself in the same way that skeletal muscle does?

The reason is in that amazing ‘intrinsic tendency to beat’ that we talked about before.

For a tissue to repair itself, its cells have to multiply, and for them to multiply, they have to divide.

“Cardiac cells are specialized to contract, so they are full of contractile myofilament proteins,” says the expert.

If one of those cells were to divide to form another, “you would have to take all of that apart and then reassemble all the contractile machinery.”

But while that’s going on, they wouldn’t be able to contract, and since the heart is in continual use, it can’t afford that on a large scale.

The fact that it can’t stop, because that would be fatal, inhibits the heart’s ability to repair itself.

“If you look very closely, you can see maybe 1% of heart muscle cells dividing over a year. That’s very, very low, and not enough to regenerate the heart,” says Sinha.

So the best thing, as always, is to take care of it.

How?

“What we tend to advise at the moment, and this is just a guideline,” says cardiologist Rohin Francis, “is to do some activity that leaves you a little breathless for at least half an hour three times a week.”

* This article is based on part of the episode “The painless heart” from the BBC series “The curious cases of Rutherford & Fry”.

Remember that you can receive notifications from BBC Mundo. Download the new version of our app and activate it so you don’t miss out on our best content.

• Do you already know our YouTube channel? Subscribe!