Breathing and Exchange of Gases

Regulation of Respiration

What is respiration?Do humans have the ability to regulate their breathing? Yes, they do! Human beings can control their respiration to suit the demands of the body tissues. Which body system do you think is responsible for this regulation? It is the nervous system. Special centres in the nervous system called ‘The respiratory centres of the brain’ regulate different aspects of respiration. Let’s learn about how these centres regulate respiration.

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Respiration Centres Of The Brain

The neuronal signals transmitted between respiratory centres of the brain and the muscles in the chest and diaphragm modulate respiration. There are three main centres of the brain that regulate breathing. They are present in the medulla and the pons region of the brain. They regulate breathing by stimulating the contraction of the intercostal muscles and the diaphragm. Let’s take a closer look at these different centres.

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In Medulla

Respiratory Rhythm Centre

Inspiration is followed by expiration, thus creating a regular, oscillating cycle of breathing. This is the respiratory rhythm. A special centre in the medulla region of the brain is primarily responsible for regulating respiratory rhythms. This is the ‘Respiratory Rhythm Center’. This centre produces rhythmic nerve impulses that contract the muscles responsible for inspiration (diaphragm and external intercostal muscles).

Normally, expiration happens when these muscles relax. However, in case of rapid breathing, this centre stimulates the muscles responsible for expiration (internal intercostal muscles and abdominal muscles).

In The Pons

Pneumotaxic Centre

This centre regulates the functions of the respiratory rhythm centre. It controls both the rate and pattern of breathing. The pneumotaxic centre can send neural signals to reduce the duration of inspiration, thereby affecting the rate of respiration. The actions of this centre prevent the lungs from over-inflating.

It also regulates the amount of air that the body takes in, in a single breath. If this centre is absent, it increases the depth of breathing and decreases the respiratory rate. It performs the opposite function of the Apneustic centre described below.

Apneustic Centre

This centre promotes inspiration by constantly stimulating the neurons in the medulla region. It sends signals that oppose the action of the signals from the pneumotaxic centre. It sends positive signals to the neurons that regulate inspiration, thereby controlling the intensity of breathing.

what is respiration

Respiratory Centers of the Brain (Source: Wikimedia Commons)

There also exists a chemosensitive area in the brain stem adjacent to the respiratory rhythm centre. It is highly sensitive to CO2 and hydrogen ions. Increase in CO2 and H+ ions activate this centre, which in turn signals the rhythm centre to adjust the respiratory process and eliminate these substances.

In addition to respiratory centres, there are certain receptors also that can detect changes in CO2 and H+ ion concentration and send signals to regulate breathing. Some of these are chemoreceptors located in the medulla, aortic arch, and carotid artery whereas some are receptors in the walls of bronchi and bronchioles.

Some factors that affect the rate of respiration are:

A Solved Example For You

Q: Which respiratory centres work against each other and together control the rate of respiration?

  1. Pneumotaxic centre and Apneustic centre
  2. Apneustic centre and Rhythm centre
  3. Pneumotaxic centre and Rhythm centre
  4. Chemosensitive area and Apneustic centre

Solution: The answer is ‘a’. The Pneumotaxic centre prevents over-inflation of the lungs, while the apneustic centre promotes over-inflation, thus controlling the rate of respiration.

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