A while ago I read a prank online. It was

Now you are breathing manually.

It got me manually breathing then just as it got you now. This spurred me into thinking about the mechanics of how different parts of our respiratory system operate, how is the air actually inhaled and exhaled and what part/parts of our brain control it. Let me tell you what I learnt.

Moving with the air

Let us first take a short trip inside our bodies to understand how the air we breathe travels inside us.

1. Taking a breath

When you take a breath, the air goes through your nose and/or mouth, down your throat and into the trachea (also known as windpipe).

2. Into the lungs

The end of trachea splits into an upside down Y-shape (something like this ⅄), thus forming the two bronchi (bronchus for singular). Air passes through left or right bronchus into respective lung.

3. Climbing the branches of the bronchial tree

Inside the lungs, each bronchus branch off into a tree-like structure of bronchioles. The air flows through bronchioles, which keep getting smaller, until it reaches the end of branches.

4. Filling up countless tiny balloons

At the end of each bronchiole, there is a tiny balloon like tissue structure called alveolus (plural alveoli) which forms an air pocket where external air is collected.

5. Gas exchange

When the air reaches the alveoli, a process similar to osmosis dissolves the oxygen from the air into capillaries while extracting carbon-dioxide from blood into the air inside alveoli at the same time.

6. The journey back to surface

The exhale phase starts at this moment and the air in the alveoli travel back to outside world following the same path it came in. That is

  1. Alveoli
  2. Bronchiole
  3. Bronchi
  4. Trachea
  5. Throat
  6. Nose/Mouth
  7. Sweet freedom of outside world

Mechanics of all these

There are 2 main mechanical processes:

  1. How is air inhaled?
  2. Consequently, how is it exhaled afterwards?

1. Inhaling the external air

When we want to inhale, the diaphragm (a large dome-shaped muscle located below the lungs) and the muscles between our lungs and rib-cage contract, thus creating a vacuum (more precisely they create a negative air-pressure). This forces the external air to enter our lungs through the path mentioned earlier.

2. Exhaling the inside air

Subsequently, when we want to exhale the air that we inhaled into the lungs, the same muscles (diaphragm and the muscles between lungs and rib-cage) relax. This creates a positive air-pressure inside lungs which forces the air inside them to go out.

Controlling our breathing

Finally returning to my original question of, "How is the actual breathing controlled? Who determines whether we breath manually or autonomously?"

There is a part of our brain aptly named "Respiratory center". Respiratory center (RC) is responsible for generating and maintaining the rhythm of respiration. They receive control/sensor signals of neural, chemical and hormonal nature. After processing these signals, this center sends down the appropriate signal(s) to the muscles involved in breathing. These signals ensure that your breathing muscles contract and relax regularly, thus allowing the breathing to be automatic without us even being aware of it.

Although to a limited degree we can also affect our breathing rate. The cerebral-cortex sends one of the control signal to RC. This allows us to do things like holding our breath, breathing faster/slower than usual consciously.

Our emotions can also affect our breathing pattern. Like being scared or angry can increase our respiratory rate. It also depends upon how physically active we are at the moment or what are the conditions of air around us.

Two of the main sensor systems for respiratory regulations are:

  1. Sensors in the brain and the 2 major blood vessels (the carotid artery and the aorta) detect levels of CO2 and O2 mixed in the blood and change our breathing as needed.
  2. Sensors in the airways (mouth, nose, trachea etc.) detect lung irritants. These sensors are generally responsible for triggering sneezes or coughs. After all sneezing and coughing are a form of sharp exhale of air from lungs.

That's all folks

These are my finding when I went down the Internet lanes to find the answer of "How is our breathing rate controlled?". If you have any other suggestions regarding these or any other topics under the sky, contact me or tweet to me @varun_barad.

Disclaimer

I am not a doctor and I don't pose as one on the internet. This post is just a compilation of what I found while learning about this topic.

Sources