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Regulation of Respiration

  • Respiration can be regulated voluntarily, like while doing yoga.
  • But usually, it is regulated involuntarily by both the nervous system and chemosensory receptors.

    regulation-of-respiration


Topics covered:

  • Neural Regulation
  • Chemical Regulation
  • Hering-Breuer reflex

Neural Regulation


Introduction:

  • Nervous system regulates the respiratory rhythm through various respiratory centres present in the brain.
  • Parts of the brain that participate in neural regulation are:
    A.  Medulla oblongata
    B.  Pons varolii

Explanation
 

A. Medulla oblongata

  • Medulla has 2 respiratory centres:
    1. Dorsal neuron group
    2. Ventral neuron group

A.1. Dorsal neuron group (DNG)a

Located in the dorsal aspect of medulla.
Maintains respiratory rhythm and respiratory rate.
As inspiration is an active process, DNG regulates the process of inspiration.
Therefore it is also called as inspiratory centre or respiratory rhythm centre.

A.2. Ventral neuron group (VNG)

Responsible for regulation of forceful expiration.
Also known as expiratory centre.

B. Pon varolii

  • Pons has got two regulatory centres:
    1. Pneumotaxic centre
    2. Apneustic centre

B.1. Pneumotaxic centr

It is activated in presence of toxic gases like CO2
It switches off or inhibits inspiratory centre, hence called as inspiratory cut off centre
In this condition, breathing is shallow and rapid

B.2. Apneustic centre

It is associated centre of pneumotaxic centre
 

regulation-of-breathing


Chemical Regulation


Introduction:

  • Also called chemosensory regulation.
  • Centres are associated with chemical regulation:
    A. Central chemoreceptors
    B. Peripheral chemoreceptors

A. Central chemoreceptors

  • Present in the medullary region around the inspiratory centre
  • This area is sensitive to pCO2 and H+ ions concentration.
  • So an increase in pCO2 and H+ ions activate these receptors, which in turn activate the inspiratory centre or respiratory rhythm centre.
  • Activated rhythm centre alter the rate of respiration or inspiration.

B. Peripheral chemoreceptors

  • These include:
    1. Aortic bodies - Chemoreceptors present in aortic artery.
    2. Carotid bodies - Chemoreceptors present in carotid artery.
  • These are activated by increase in pCO2 and H+ ions in arterial blood.
  • These activate the inspiratory centre or respiratory rhythm centre to reverse the situation.


    1


Hering-Breuer Reflex


Definition:

“Hering-Breuer reflex is a reflex initiated to prevent the over-inflation of the lungs.”

Detailed Explanation:

  • It is a protective reflex mechanism that helps in respiratory regulation.
  • Stretch receptors are present in the wall of bronchi and bronchioles.
  • Overstretching of lungs and airways activates the stretch receptors, which send the nerve impulse to medulla through the vagus nerve,to inhibit the inspiration.
  • With the inhibition of inspiration, expiration begins.


Frequently Asked Questions - FAQs

Q1. What are the parts of the brain that participate in neural regulation?
Ans.
Parts of the brain that participate in neural regulation are:
A. Medulla oblongata
B. Pons Varolii

Q2. What activates the central chemoreceptors centre?
Ans.

- The central chemoreceptors area is sensitive to pCO2 and H+ ions
- So, increase in pCO2 and H+ ions activate the receptors.

Q3. Where is the pneumotaxic centre located in the brain?
Ans. 

Pneumotaxic centre is located in the pons varolii.

Q4. How does pneumotaxic centre alter the respiratory rate?
Ans. 
In the presence of toxic gases like CO2, it gets activated. - It switches off or inhibits the inspiratory centre, hence called as inspiratory cut off centre.

Q5. What is the purpose of the Hering-Breuer reflex?
Ans. 
Hering-Breuer reflex is a protective mechanism that prevents over-inflation of lungs - Walls of bronchi and bronchioles have stretch receptors that get activated on the inflation of lungs - On activation nerve impulses are sent to inhibit the inspiratory rate

Q6. How do peripheral chemoreceptors regulate rate of respiration?
Ans.
Peripheral chemoreceptors (aortic and carotid bodies) are activated by increase in pCO2 and H+ ions in arterial blood - On activation, these in return activate the inspiratory centre or respiratory rhythm centre to reverse the situation by increasing the respiratory rate

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