Mechanism of Breathing
The mechanism of breathing involves the events that occur during two processes, i.e. inhalation or inspiration and exhalation or expiration. The events involved are given below:
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Events During Inspiration |
Events During Expiration |
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The respiratory centre initiates the stimulus/stimuli. |
The respiratory centre terminates the stimulus/stimuli. |
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Diaphragm and expiratory muscles contract. |
Diaphragm relaxes and internal intercostal muscles contract. |
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Thoracic volume increases because the chest wall expands. |
Thoracic volume decreases because the chest wall contracts. |
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Intra-pulmonary pressure (inside the lungs) is reduced. |
Intra-pulmonary pressure (inside the lungs) is increased. |
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Alveolar pressure decreases more than atmospheric pressure. |
Alveolar pressure increases more than atmospheric pressure. |
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Air is taken inside due to the expansion of the alveoli. |
Air is given out due to the contraction of the alveoli. |
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Air rushes into the alveoli until the alveolar pressure equalizes to the atmospheric pressure and the alveoli become inflated. |
Air rushes out of the alveoli until the alveolar pressure equalizes to the atmospheric pressure and the alveoli become deflated. |
NCERT Notes Class 11 Biology Chapter 14 – Breathing and Exchange of Gases
Notes for NCERT Class 11 Biology Chapter 14 Breathing and Exchange of Gases: Breathing (ventilation) is a process of moving air into and from the lungs so that the exchange of gases can be taken place with the internal environment. The main purpose is to expel carbon dioxide and take in oxygen. Respiration is a process in which the cells of an organism get energy by the oxidation or burning of the glucose molecules when we inhale oxygen from the air. The liberated energy is used up by our body to perform some functions like muscle contraction, nerve impulse transmission, protein synthesis, etc. There are some organs involved in these processes which perform specific functions.
Class 11 Biology Chapter 14 Breathing and Exchange of Gases: Explains the respiratory system is the network of many organs which help in breathing. It comprises the airways, lungs and blood vessels. These work together to transport oxygen throughout the body and clean out the waste gases like carbon dioxide. The respiratory system performs many functions. It helps to inhale (breathe in) and exhale (breathe out), allows us to talk and to smell. It also helps to deliver oxygen to the cells, warms up the air according to the body’s temperature and moisturises it to the humidity level according to the need. Removal of gases waste, including carbon dioxide, is another job, it performs. Some conditions may affect the organs and tissues of the respiratory system. Some may be developed due to the irritants we inhale from the air, including viruses or bacteria which cause infection.