Breathing - It's all about the Rhythm, but what is the Nervous System's Role

You may think you are Breathing voluntarily, but your Brain says different!

The Nervous System plays a key role in generating a normal breathing rhythm.

The Diaphram is an integral part of the Pulmonary System, and is supplied with Spinal Nerves via segments c3, c4 and c5 of the Spinal Cord.

The nerves are connected to the Medulla Oblongta, which is a control centre for respiration. It is located in the lower part of the Brain Stem.
There is a second respiratory centre in the Pons, of which the nerves are also connected. This control centre is located above the Medulla Oblongata.

The interaction between these two particular respiratory centres enable automatic breathing.

Autonomic control of breathing is achieved by the respiratory system and the nervous system being conected by stretch receptors, sensory nerves and the vagus nerve.
The vagus is a cranial nerve which starts in the medulla and continues through the body. It conveys sensory information to the brain on how all the bodys organs are performing.

For autonomic control of breathing the bronchi and bronchioles contain stretch receptors in their walls, which are stimulated when the lungs inflate during inspiration. These receptors are connected to the sensory nerves which send action potentials along the vagus nerve to inhibit the inspiratory centre in the medulla.
This makes inspiration stop so expiration can start. When the lungs deflate the stretch receptors stop sending action potentials to the inspiratory centre so inhibition stops, and allows inspiration to start again.



Now for the technical bit....

• The diaphragm and the intercostal muscles can only contract once they have received an action potential from the medulla


• The centres within the medulla which control the basic Breathing Rhythm are connected to the muscles by motor nerves of the autonomic nervous system


• The inspiratory centre stimulates contractions of the diaphragm and external intercostal muscles, and inhibits the expiratory centre


• As soon as inspiration is complete, the inspiration centre centre stops inhibiting the expiration centre


• When the expiratory centre operates it inhibits the inspiratory centre, so the diaphragm and external intercostal muscles relax


• The inhibition means that both the inspiratory and expiratory centres cannot stimulate the lungs at the same time, this results in a basic breathing rhythm being established

Photos sourced from:

www.infovisual.info

www.apsu.edu

Bibliography

CG Partnership handout, wk 24, Structure and function of the respiratory system

CG Partnership handout, wk 22, The Pulmonary system

Wikipedia