Breathing Mechanics explained

Nitzan Arad
Sep 13, 2024
2 min read

Updated: Jul 10

Take a deep breath in.

Now, slowly let it all out.

Feel the difference? Let's explore the mechanics behind it.

The Cycle:

We breathe to exchange oxygen for carbon dioxide. Here's a quick breakdown:

Inhalation:

Diaphragm and Intercostal muscles contract, creating more space for the lungs to expand and reducing pressure in the lungs that suck the air in.
Air rich in oxygen (21.1%) fills the lungs.

Gas Exchange:

Oxygen travels through alveoli into red blood cells using the hemoglobin molecule. This blood travels through the arteries in the body and into the tissues.
The cells use the oxygen for metabolism, and at the end of the process - carbon dioxide (CO2) is produced as a byproduct that diffuses back into the bloodstream.

Exhalation:

Blood, now enriched with CO2, returns to the lungs by the venous system.
The diaphragm and intercostals relax, moving upward inward and pressing on the lungs to expel CO2 from the body.

This entire process happens 12 to 20 times per minute, moving about 6-10 liters of air in and out.

What does breathing have to do with the Nervous system?

Vagus Nerve is the answer.

Due to Anatomical proximity and physiological interaction - the diaphragm and the vagus nerve affect each other.

The diaphragm -

is a dome-shaped muscle beneath the lungs, innervated by the phrenic nerve (C3-5).
It is one of the core muscles and is the most important muscle of inspiration.
Except for breathing, It also participates in swallowing, coughing, sneezing, vocalization, vomiting, and even giving birth.

The vagus nerve (cranial nerve #10, and the longest one of them) -

is responsible for 75% of the Parasympathetic Nervous system's actions, which, together with the sympathetic system, makes up the Autonomic nervous system (ANS).
It is composed of sensory and motor nerve fibers and is an essential pathway in regulating food intake and energy metabolism.

The Parasympathetic system is the one responsible for the “rest and digest” mode. It has control over digestion, heart rate, and immune system.

The sympathetic system is the "Fight, Flight or Freeze” system, taking action during stressful events that require our response.

The Connection -

The vagus runs from the brain to the lower body parts and crosses through the diaphragm!

In the passage through the diaphragm, the vagus nerve is connected directly to the diaphragm and esophagus by connective tissue and small muscular fibers.

And since the vagus is autonomous (= out of our conscious control), we can effect this interaction only by using the diaphragm.

When the diaphragm engages in deep, purposeful breathing, it stimulates the vagus nerve, initiating a cascade of physiological responses: Heart rate decreases, blood pressure stabilizes, and a sense of calm permeates the body.

The bottom line

Deep, intentional breathing with prolonged exhalation activates the vagus nerve and the Parasympathetic Nervous system > offering a simple yet powerful tool to reduce stress and promote calmness.

Main Scientific Resources that helped me with this blog post -