Breathing Definition

Breathing or exchange of gases is very important for the human body. The process of respiration can only be achieved with the help of breathing. Respiration is the process where the oxygen from the environment is utilized for the purpose of breaking down the food and helps in providing us energy. Breathing involves the intake of oxygen and the expiration of carbon dioxide and thus is the most crucial process. The process of respiration is controlled by different parts of the body. The action of breathing or the control of respiration in humans is not under our control. It is therefore an involuntary action. A normal human or adult breathes 12-16 times per minute. The process of inspiration lasts for around 2 seconds and the process of expiration lasts for around 3 seconds. According to the needs of the body, the rate and amount of breathing can be controlled. Two types of control of breathing human respiratory system are present. They are Nervous regulation and Chemical regulation. 

Nervous Regulation

As the name suggests, the rate of breathing is controlled by the nervous system. There are various respiratory centres that are present in the brain and they are responsible for the control of breathing human respiratory system. There are a group of neurons that are present in the brain and they are named medulla oblongata and pons. They help in controlling the rate and depth of breathing. Respiration is controlled by two centres that are: 

  • Respiratory Rhythm Centre: As we read above this centre is present in the medulla region of the hindbrain. It is a specialized centre that helps in the control of respiration. According to the neurons, it helps in controlling the activity of inspiration or expiration. This happens when the neurons are activated. This control of breathing takes place according to the need of the body. 

  • Pneumotaxic Centre: In the pons region of the hindbrain this centre is present. It is the respiratory rhythm centre, which means that this centre is responsible for controlling or setting up the rhythm of breathing. The rate of breathing is controlled by sending nerve impulses that can increase or decrease the amount of inspiration and expiration. This helps in affecting the overall respiration rate. 

Chemical Regulation

Just close to the rhythm centre, we have a centre that is responsible for the chemical regulation of respiration. It is a chemosensitive area which means that it is sensitive to chemicals and it has the presence of chemical receptors. These receptors are sensitive to hydrogen ions and carbon dioxide gas. Respiration is controlled by the concentration or the partial pressure of the above two chemicals. When there is an increase in the concentration of hydrogen ions or the levels of carbon dioxide then this centre is activated. The sensitive receptors or the hydrogen ions and the carbon dioxide are located in the aortic arch. They are also present in the carotid artery. This artery is responsible for supplying blood to the brain. The oH of the body is decreased when there is a high amount of carbon dioxide and when the amount of carbon dioxide is low then the pH of the body is increased. So the rate of breathing is controlled by the chemical receptors. Narcosis is a disease or depression of the central nervous system. This affects the rate of respiration and then affects the regulation of respiration. 


There are a pair of lungs present in human beings. They are present in the thoracic cavity and it is an air-tight chamber. The thoracic cavity is also known as the chest cavity. This cavity is present on the dorsal side of the vertebral column, and on the ventral side, the sternum is present. Ribs are present on the lateral side of the lungs. Below the lungs, the diaphragm is present. This is a dome-shaped structure and it is made up of muscles. This is also responsible for separating the thoracic cavity and abdominal cavity. Pleura and pleural membrane are the two membranes that help in enclosing the lungs. With the thoracic cavity, the outer pleural membrane is in very close contact. And with the lung’s surface, the inner pleural membrane is in close contact. Pleural fluid is the fluid that is present in the fluid cavity. This fluid is secreted by the pleural membrane. The inner layer is called the visceral pleura and the parietal pleura is the outermost layer.

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Steps of Respiration

There are five steps that are involved in respiration. 

  • Breathing: Breathing is a simple process that involves taking in oxygen and then throwing out the carbon dioxide to the environment. Pulmonary ventilation is the other name for breathing. 

  • Diffusion of Gases: After breathing, the gases are then diffused between the alveoli and the blood. Oxygen and carbon dioxide are exchanged across the alveolar membrane. This membrane is very thin and thus this helps in the exchange of gases.

  • Transport of Gases: The gases are transported with the help of blood. 

  • Diffusion of Gases Between Blood and Tissues: The oxygen is diffused into the blood and the carbon dioxide is diffused from the tissues to the blood. 

  • The Utilisation of Oxygen: The oxygen is then utilized by the cells and parts of the body. 

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FAQs on Control of Breathing

1. What are Occupational Respiratory Disorders?

Answer: These are the disorders that are related to the respiratory system and the cause of these disorders is working in factories under stressful conditions. They are caused when gases, fumes, and dust are exposed continuously to them. Some common names of the diseases that are caused are Silicosis and Asbestosis. They are caused by continuous exposure to dust at the workplace. The upper part of the lungs is damaged and the fibrosis of the upper part of the lungs occurs. The redness and swellings of the lungs take place. To avoid this, the workers should wear masks, and also long exposures to such conditions should be avoided. 

2. What is the Route Followed at the Time of Breathing?

Answer: The external nostrils are the first part that inhales the air from outside. It then travels through the internal nares and nasopharynx to the glottis. The glottis is a part of the larynx. From the larynx, it travels through the trachea and then goes into the primary bronchi. From the primary bronchi, it goes to secondary bronchi and then to tertiary bronchi. Then it reaches bronchioles and from them to the alveolar duct and then the atria sac and the alveoli. 

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