Go Ahead And Let Out That Long Sigh — It's Good For You!


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Just when we think there couldn't possibly be any more mysteries left to solve about the human anatomy, comes another discovery. This one has to do with sighing. It turns out that the involuntary reflex that is generally associated with sadness or despair is crucial to our well-being. That is why researchers at the University of California, Los Angeles, and Stanford University were determined to find out what triggers the spontaneous action, without which our lungs would collapse!

A sigh is just a deep breath which starts out as a normal breath but extends when we inhale more air before letting it out. And while you may not realize it, most of us sigh once about every five minutes, or approximately twelve times an hour, regardless of whether we are sad or depressed.

To understand why we need to learn a little about how the lungs function. As you are probably aware, our lungs comprise of many branches or bronchioles each of which divides into millions of tiny sacs called alveoli. The alveolus (singular for alveoli) is where the respiratory system comes in contact with the circulatory system and conducts the all-important exchange of oxygen and carbon dioxide. The sacs inflate and collapse as we breathe in and out. However, the alveoli need to be inflated completely to avoid them from collapsing. Since that cannot be accomplished with just regular breathing, our body takes a deep breath or what we call a 'sigh' every few minutes.

Photo Credit: Med-health.net

Though scientists have known this for many years, they had not been able to identify what triggers this involuntary life-sustaining reflex. However, two previous studies - One conducted by the University of California, Los Angeles and the other at Stanford University had found the answer to half the puzzle — Now thanks to a collaboration between the two institutions, the mystery has been finally solved.

The study conducted by Stanford researcher Mark Krasnow and his team had identified the 200 neurons in the brain cells that are responsible for releasing two peptides, protein fragments that allow the brain cells to 'talk' to each other. What they could not figure out was which brain cells they were communicating with and more importantly what they were instructing them to do. Meanwhile, UCLA neurology professor Jack Feldman and his team had discovered that the same family of peptides, (common to both mice and humans) were very involved in the part of the brain that controls breathing.

On each side of the brain stem, a florescent-green marker illuminates the two networks of 200 neurons that control the sighing reflex (Photo Credit: Stanford/Krasnow lab

The two combined their knowledge to conduct further studies on mice. They discovered that the peptides triggered the nerve cells that activate the rodent's muscles, which in turn instigate the involuntary sighs. The researchers said that when they blocked one set of peptides the mice sighed at half the rate. When the peptides were blocked completely, the mice stopped sighing altogether. Conversely, when the peptides were increased the number of sighs went up substantially — From 40 times an hour to 400 times!

The study which was published in the digital edition of the science journal, Nature, on February 8, opens the possibilities of new medications to help people with severe respiratory conditions. It will also assist in a more efficient design of life support systems. But most important of all, it gives us a compelling reason to sigh! So go ahead and let out a long deep one — It will do your body good!

Resources: Theguardian.co.uk, newsroom.ucla.edu

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