The physiological definition of respiration differs from the biochemical definition, which refers to cellular respiration, a metabolic process by which an organism obtains energy (in the form of ATP) by oxidizing nutrients and releasing waste products. Although physiologic respiration is necessary to sustain cellular respiration and thus life in animals, the processes are distinct: cellular respiration takes place in individual cells of the organism, while physiologic respiration concerns the diffusion and transport of metabolites between the organism and the external environment.
In animals with lungs, physiological respiration involves respiratory cycles of inhaled and exhaled breaths. Inhalation (breathing in) is usually an active movement. The contraction of the diaphragm muscle cause a pressure variation, which is equal to the pressures caused by elastic, resistive and inertial components of the respiratory system. In contrast, exhalation (breathing out) is usually a passive process. Breathing in, brings air into the lungs where the process of gas exchange takes place between the air in the alveoli and the blood in the pulmonary capillaries
The process of breathing does not fill the alveoli with atmospheric air during each inhalation (about 350 ml per breath), but the inhaled air is carefully diluted and thoroughly mixed with a large volume of gas (about 2.5 liters in adult humans) known as the functional residual capacity which remains in the lungs after each exhalation, and whose gaseous composition differs markedly from that of the ambient air. Physiological respiration involves the mechanisms that ensure that the composition of the functional residual capacity is kept constant, and equilibrates with the gases dissolved in the pulmonary capillary blood, and thus throughout the body. Thus, in precise usage, the words breathing and ventilation are hyponyms, not synonyms, of respiration; but this prescription is not consistently followed, even by most health care providers, because the term respiratory rate (RR) is a well-established term in health care, even though it would need to be consistently replaced with ventilation rate if the precise usage were to be followed.
Classifications of respirationEdit
There are several ways to classify the physiology of respiration:
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- Huff and puff
- Selected ion flow tube mass spectrometry
- Bell Jar Model Lung
- Sudden Infant Death Syndrome
- Myasthenia gravis
- Severe acute respiratory syndrome
- Pulmonary aspiration - Pulmonary edema
By intensive care and emergency medicineEdit
- Mechanical ventilation
- Iron lung
- Intensive care medicine
- Liquid breathing
- Oxygen toxicity
- Medical ventilator
- Life support
- General anaesthesia
By other medical topicsEdit
- Nelsons VCE Units 1-2 Physical Education. 2010 Cengage Copyright.
- Overview at Johns Hopkins University
- Clinical Sciences - Respiratory An iPhone app covering detailed respiratory physiology and anatomy
- Nilsson, Goran E. (2010). Respiratory Physiology of Vertebrates. Cambridge: Cambridge University Press. ISBN 978-0-521-70302-4.
- Randall, David (2002). Eckert Animal Physiology. New York: W.H. Freeman and CO. ISBN 0-7167-3863-5., human biology 146149
- C.Michael Hogan. 2011. Respiration. Encyclopedia of Earth. Eds. Mark McGinley and C.J.Cleveland. National Council for Science and the Environment. Washington DC