respiration

respiration,

process by which an organism exchanges gases with its environment. The term now refers to the overall process by which oxygen is abstracted from air and is transported to the cells for the oxidation of organic molecules while carbon dioxide (CO₂) and water, the products of oxidation, are returned to the environment. In single-celled organisms, gas exchange occurs directly between cell and environment, i.e., at the cell membrane. In plants, gas exchange with the environment occurs in special organs, the stomates, found mostly in the leaves (see leafleaf,
chief food-manufacturing organ of a plant, a lateral outgrowth of the growing point of stem. The typical leaf consists of a stalk (the petiole) and a blade—the thin, flat, expanded portion (needlelike in most conifers) that is normally green in color because of the
..... Click the link for more information. ; transpirationtranspiration,
in botany, the loss of water by evaporation in terrestrial plants. Some evaporation occurs directly through the exposed walls of surface cells, but the greatest amount takes place through the stomates, or intercellular spaces (see leaf).
..... Click the link for more information. ).

Organisms that utilize respiration to obtain energy are aerobic, or oxygen-dependent. Some organisms can live in the absence of oxygen and obtain energy from fuel molecules solely by fermentationfermentation,
process by which the living cell is able to obtain energy through the breakdown of glucose and other simple sugar molecules without requiring oxygen. Fermentation is achieved by somewhat different chemical sequences in different species of organisms.
..... Click the link for more information. or glycolysisglycolysis
, term given to the metabolic pathway utilized by most microorganisms (yeast and bacteria) and by all "higher" animals (including humans) for the degradation of glucose. Glycolysis means, literally, the dissolution of sugar.
..... Click the link for more information. ; these anaerobic processes are much less efficient, since the fuel molecules are merely converted to end products such as lactic acid and ethanol, with relatively little energy-rich ATP produced during these conversions.

For individual respiratory organs, see separate articles.

Animal Respiration

In complex animals, where the cells of internal organs are distant from the external environment, respiratory systems facilitate the passage of gases to and from internal tissues. In such systems, when there is a difference in pressure of a particular gas on opposite sides of a membrane, the gas diffuses from the side of greater pressure to the side of lesser pressure, and each gas is transported independently of other gases. For example, in tissues where carbon dioxide concentration is high and oxygen concentration is low as a result of active metabolism, oxygen diffuses into the tissue and carbon dioxide diffuses out.

In lower animals, gas diffusion takes place through a moist surface membrane, as in flatworms; through the thin body wall, as in earthworms; through air ducts, or tracheae, as in insects; or through specialized tracheal gillsgills,
external respiratory organs of most aquatic animals. In fishes the gills are located in gill chambers at the rear of the mouth (pharynx). Water is taken in through the mouth, is forced through openings called gill slits, and then passes through the gill clefts, spaces
..... Click the link for more information. , as in aquatic insect larvae. In the gills of fish the blood vessels are exposed directly to the external (aquatic) environment. Oxygen–carbon dioxide exchange occurs between the surrounding water and the blood within the vessels; the blood carries gases to and from tissues.

In other vertebrates, including humans, gas exchange takes place in the lungslungs,
elastic organs used for breathing in vertebrate animals, excluding most fish, which use gills, and a few amphibian species that respire through the skin. The word is sometimes applied to the respiratory apparatus of lower animals.
..... Click the link for more information. . Breathing is the mechanical procedure in which air reaches the lungs. During inhalation muscular action lowers the diaphragm and raises the ribs; atmospheric pressure forces air into the enlarged chest cavity. In exhalation the muscles relax and the air is expelled. This combined rhythmic action takes place about 12–16 times per minute when the body is at rest. The rate of breathing is controlled mainly by a respiratory center in the brain stem that responds to changes in the level of hydrogen ion and carbon dioxide in the blood, as well as to other factors such as stress, temperature changes, and motor activities. Some residual air always remains in the lungs, but with each breath an additional quantity of fresh air, called tidal air, is inhaled. Artificial respirationartificial respiration,
any measure that causes air to flow in and out of a person's lungs when natural breathing is inadequate or ceases, as in respiratory paralysis, drowning, electric shock, choking, gas or smoke inhalation, or poisoning.
..... Click the link for more information. is used for respiratory failure.

In higher vertebrates, oxygen-poor, carbon dioxide–rich blood from the right side of the heart is pumped into the lungs and flows through the net of capillaries surrounding the alveoli, the cup-shaped air sacs of the lungs; oxygen diffuses across the capillary membranes into the blood, and carbon dioxide diffuses in the opposite direction. The oxygen combines with the protein hemoglobin in red blood cells as the blood returns to the left side of the heart, is pumped throughout the body, and is released into tissue cells (see circulatory systemcirculatory system,
group of organs that transport blood and the substances it carries to and from all parts of the body. The circulatory system can be considered as composed of two parts: the systemic circulation, which serves the body as a whole except for the lungs, and the
..... Click the link for more information. ). Carbon dioxide passes in the opposite direction, from the cells of the tissues to the red blood cells. In the blood, carbon dioxide exists in three forms: as bicarbonate ion, in which form it serves as a buffer, keeping blood acidity fairly constant; combined with hemoglobin; and as the dissolved free gas. Of these, only free carbon dioxide gas is available for diffusion from the blood into the lungs.

Biochemical Respiration

In biochemistry, respiration refers to the series of biochemical oxidations in which organic molecules are converted to carbon dioxide and water while the chemical energy thus obtained is trapped in a form useful to the cell. Biochemical respiration occurs in both plant and animal cells. Carbohydrates, amino acids, and fatty acids—the organic fuel molecules of the cell—can be converted to acetyl CoA, a derivative of acetic acid and coenzymecoenzyme
, any one of a group of relatively small organic molecules required for the catalytic function of certain enzymes. A coenzyme may either be attached by covalent bonds to a particular enzyme or exist freely in solution, but in either case it participates intimately in
..... Click the link for more information. A.

Acetyl CoA then enters a series of reactions in the mitochondria, organelles in the cell's cytoplasm. The series of reactions, known as the Krebs cycleKrebs cycle,
series of chemical reactions carried out in the living cell; in most higher animals, including humans, it is essential for the oxidative metabolism of glucose and other simple sugars.
..... Click the link for more information. , converts the acetic acid portion of acetyl CoA to carbon dioxide, protons, and hydride ions, the latter usually as part of the coenzyme NADH. This molecule is oxidized back to NAD when it donates the hydride ion to the series of enzymes known as the electron transport chain. In a process called oxidative phosphorylationphosphorylation,
chemical process in which a phosphate group is added to an organic molecule. In living cells phosphorylation is associated with respiration, which takes place in the cell's mitochondria, and photosynthesis, which takes place in the chloroplasts.
..... Click the link for more information. , each electron transport enzyme is in turn reduced (receives the hydride ion), then oxidized (donates a hydride ion to the next enzyme in the series), and the chemical energy liberated in this series of reactions is coupled to the synthesis of adenosine triphosphateadenosine triphosphate
(ATP) , organic compound composed of adenine, the sugar ribose, and three phosphate groups. ATP serves as the major energy source within the cell to drive a number of biological processes such as photosynthesis, muscle contraction, and the synthesis of
..... Click the link for more information. (ATP) from adenosine diphosphate (ADP) and phosphoric acid.

ATP, the cell's form of energy storage and supply, furnishes the chemical energy needed for muscle contraction, protein synthesis, active transport of substances across membranes, and electrical impulses. At the end of the electron transport chain, a hydride ion is donated to an atom of oxygen; this pair, together with a proton from the surrounding solution, forms a molecule of water. Thus, in the overall process of cellular respiration, the fuel molecules are converted to carbon dioxide and water while the chemical energy gained is trapped in a useful form as ATP.

Respiration

The various processes associated with the biochemical transformation of the energy available in the organic substrates derived from foodstuffs, to energy usable for synthetic and transport processes, external work, and, eventually, heat. This transformation, generally identified as metabolism, most commonly requires the presence of oxygen and involves the complete oxidation of organic substrates to carbon dioxide and water (aerobic respiration). If the oxidation is incomplete, resulting in organic compounds as end products, oxygen is typically not involved, and the process is then identified as anaerobic respiration. See Metabolism

The term “external respiration” is more appropriate for describing the exchange of O₂ and CO₂ between the organism and its environment. In most multicellular organisms, and nearly all vertebrates (with the exception of a few salamanders lacking both lungs and gills), external respiration takes place in specialized structures termed respiratory organs, such as gills and lungs. See Lung, Respiratory system

The ultimate physical process causing movement of gases across living tissues is simple passive diffusion. Respiratory gas exchange also depends on two convective fluid movements. The first is the bulk transport of the external medium, air or water, to and across the external respiratory exchange surfaces. The second is the transport of coelomic fluid or blood across the internal surfaces of the respiratory organ. These two convective transports are referred to as ventilation and circulation (or perfusion). They are active processes, powered by ciliary or muscular pumps.

In all vertebrates and many invertebrates, the circulating internal medium (coelomic fluid, hemolymph, or blood) contains a respiratory pigment, for example, hemocyanin or hemoglobin, which binds reversibly with O₂, CO₂, and protons. Respiratory pigments augment respiratory gas exchange, both by increasing the capacity for bulk transport of the gases, and by influencing gas partial pressure (concentration) gradients across tissue exchange surfaces. See Blood, Hemoglobin, Respiratory pigments (invertebrate)

The physiological adjustment of organisms to variations in their need for aerobic energy production involves regulated changes in the exchange and transport of respiratory gases. The adjustments are effected by rapid alterations in the ventilatory and circulatory pumps and by longer-term modifications in the respiratory properties of blood.

Respiration

the totality of processes that ensure the entrance of oxygen into the organism and the discharge from it of carbon dioxide gas (external respiration); also, the use of oxygen by the cells and tissues to oxidize organic substances and release the energy contained in them, which is necessary for life processes (tissue respiration, cellular respiration). Anaerobic means of releasing energy are characteristic only of a small group of organisms—the so-called anaerobes. In the course of evolution respiration became the principal means of releasing energy in the overwhelming majority of organisms, and anaerobic reactions were maintained primarily as intermediate stages of metabolism.

Animals and humans. In protozoans, sponges, coelenterates and a few other organisms, oxygen (O₂) diffuses directly through the surface of the body. More complex, larger animals have special respiratory organs and a circulatory system that contains a fluid-—bloodor hemolymph, with substances capable of binding and transporting O₂ and carbon dioxide (CO₂). In insects, O₂ enters the tissues from a system of air-carrying tubules—tracheae. In aquatic animals, which use O₂ dissolved in water, the respiratory organs are gills, which are equipped with a rich network of blood vessels. Oxygen dissolved in water diffuses into the blood that circulates in the blood vessels of the gill slits. In many fish, intestinal respiration plays an important role. Air is swallowed and O₂ enters the blood vessels of the intestine. The swim bladder also plays some role in fish respiration. In many aquatic animals exchange of gases (mainly CO₂) also occurs through the skin.

In land animals external respiration is ensured primarily by the lungs. Amphibians and many other animals also respire through the skin. Birds have air sacs that are connected with the lungs, change in volume during flying, and facilitate respiration during flight. In amphibians and reptiles the air is forced into the lungs by movements of the muscles of the floor of the mouth. In birds, mammals, and humans external respiration is ensured by the rhythmic functioning of the respiratory muscles (chiefly the diaphragm and the intercostal muscles), which are coordinated by the nervous system. When these muscles contract, the volume of the thorax is increased, and the lungs (located in the thorax) expand. This causes a difference between the atmospheric pressure and the intrapulmonary pressure, and air enters the lungs (inspiration). Expiration may be passive—that is, a result of the collapse of the thorax and subsequently, of the lungs, which had been expanded during inspiration. Active expiration is caused by the contraction of certain groups of muscles. The quantity of air entering the lungs in one inspiration is called the respiratory volume.

During respiration the respiratory musculature overcomes the elastic resistance that is due to the resilience of the thorax, the draw of the lungs, and the surface tension of the alveoli. The latter, however, is significantly decreased by a substance that is active on the alveolar surface and that is secreted by the cells of the alveolar epithelium. Because of this substance the alveoli do not collapse upon expiration, and they expand easily upon inspiration. The greater the elastic resistance, the more difficult is the expansion of the thorax and lungs. During deep respiration the energy that the respiratory musculature must expend to overcome the resistance is greatly increased.

Nonelastic resistance to respiration is caused mainly by friction as the air moves through the nasal passages, throat, trachea, and bronchi. It is a function of the quality of the air current and its velocity during respiration. During tranquil breathing the current is similar to a laminar (linear) flow in the straight sections of the air passages and similar to a turbulent (whirling) flow in places of branching or narrowing. With an increase in the velocity of the current (during forced respiration), turbulence increases. A greater pressure difference is required for passage of the air, and consequently, there is an increase in work for the respiratory muscles. Unequal distribution of resistance to air movement along the respiratory passages leads to unequal entry of air into various groups of pulmonary alveoli. This difference in ventilation is especially significant in lung diseases.

The amount of air ventilating the lungs in one minute is called the minute respiration volume (MRV). The MRV is equal to the product of the respiratory volume and the frequency of respiration (the number of respiratory movements per minute—in humans, approximately 15-18). In an adult human at rest the MRV is 5-8 liters per minute. The part of the MRV (approximately 70 percent) that participates in the exchange of gases between the inspired and the alveolar air is the volume of alveolar ventilation. The rest of the MRV is used to flush the dead space of the respiratory tract, which, at the beginning of expiration, retains some of the air from outside with which the space had been filled at the end of the preceding inspiration. (The volume of dead space is approximately 160 milliliters [ml].) Ventilation of the alveoli ensures the constant composition of alveolar air. The partial pressures of O₂ (pO₂) and CO₂ (pCO₂) in alveolar air fluctuate within very narrow limits and total approximately 13 kilonewtons (kN) per sq m (100 mm mercury [Hg]) for O₂ and approximately 5.4 kN/m₂ (40 mm Hg) for CO₂.

Exchange of gases between alveolar air and the venous blood that enters the capillaries of the lungs occurs through the alveolar capillary membrane, whose total surface is very large (in humans, approximately 90 sq m). Diffusion of O₂ into the blood is ensured by the difference in the partial pressures of O₂ in the alveolar air and in the venous blood (8-9 kN/m², or 60-70 mm Hg). Bound carbon dioxide (bicarbonates, carbonates, and carbohemoglobin) that has been transported by the blood from the tissues is released in the capillaries of the lung with the participation of the enzyme carbonic anhydrase and diffuses from the blood into the alveoli. The difference in pCO₂ between the venous blood and the alveolar air is approximately 7 mm Hg. The capacity of the alveolar wall to pass O₂ and CO₂—the so-called pulmonary diffusing capacity—is very great. At rest it is approximately 30 ml O₂ per 1 mm of difference in pCO₂ between alveolar air and blood in one minute (for CO₂ the diffusing capacity is many times greater). Therefore, the partial pressure of the gases in the arterial blood leaving the lungs is able to approach the pressure of the gases in the alveolar air. The passage of O₂ into the tissues and the removal from them of CO₂ also occur by means of diffusion, since the pO₂ in the tissue fluid is 2.7-5.4 kN/m² (20-40 mm Hg), while in the cells it is still lower. In the cells the pCO₂ may reach 60 mm mercury.

The requirement of cells and tissues for O₂ and their formation of CO₂, which is the essence of tissue, or cellular, respiration, is one of the principal forms of dissimilation and is, in principle, accomplished in the same way in plants and animals. A high O₂ requirement is characteristic of tissues of the kidneys, the cortex of the cerebral hemispheres, and the heart. As a consequence of the oxidation-reduction reactions of tissue respiration, energy is released that is expendable for all phenomena of life. Oxidation-reduction processes occur in the mitochondria and arise from the dehydrogenation of the substrates of respiration—carbohydrates and the products of their decomposition, fats and fatty acids, and amino acids and the products of their deamination. The substrates of respiration absorb O₂ and serve as a source of CO₂. (The ratio between CO₂ and O₂ is called the respiratory quotient.) The energy released during the oxidation of organic substances is not immediately used by the tissues. Approximately 70 percent of it is expended on the formation of ATP, one of the adenosine phosphoric acids, whose subsequent enzymic decomposition supplies the energy requirements of the tissues, organs, and the body as a whole. Thus, from a biochemical point of view, respiration is the conversion of the energy of carbohydrates and other substances into the energy of macroergic phosphate bonds.

The constancy of the alveolar and arterial pO₂ and pCO₂ can be maintained only on condition that alveolar ventilation corresponds to the body’s requirement for O₂ and the formation of CO₂—that is, to the level of metabolism. This condition is met by means of the perfect regulatory mechanisms of respiration. Reflexes control the frequency and depth of respiration. Thus, an increase in the pCO₂ and a decrease in the pO₂ in the alveolar air and in the arterial blood excites the chemoreceptors of the carotid sinus and cardiac aorta, resulting in the stimulation of the respiratory center and an increase in the MRV. According to classic concepts, an increase in the pCO₂ in the arterial blood that bathes the respiratory center excites the respiratory center and produces an increase in the MRV. Thus, regulation of respiration according to the changes in the arterial pO₂ andpCO₂ is effected on the feedback principle, ensuring an optimal MRV. However, in a number of cases (for example, during muscular work) the MRV increases until the onset of metabolic shifts, which lead to changes in the gas composition of the blood. Increased ventilation is caused by signals entering the respiratory center from receptors of the motor apparatus and the motor zone of the cortex of the cerebral hemispheres, as well as by conditioned reflexes to various signals associated with habitual work and work conditions. Thus, control of respiration is effected by a complex, self-instructing system, according to the principle of regulation according to changes in the partial pressures of O₂ and CO₂ and according to signals that prevent possible deviations.

The succession of inspiration and expiration is ensured by a system of complementary mechanisms. During inspiration impulses from stretch receptors in the lungs travel along the fibers of the.vagus nerves to the respiratory center. When the lungs attain a certain volume, these impulses inhibit the cells of the respiratory center, whose excitation causes inspiration. If the nerve paths that ensure entry of impulses into the respiratory center are blocked, the rhythm of respiration is maintained by the automatism of the respiratory center. However, the rhythm is markedly different from the normal one. When there are disturbances of respiration and its regulatory mechanisms, the gas composition of the blood changes.

Methods of investigating respiration are varied. In the physiology of work and athletics and in clinical medicine, widely used techniques include recording the depth and frequency of respiratory movements, measurement of the gas composition of expired air and arterial blood, and measurement of pleural and alveolar pressure.

REFERENCES

Sechenov, I. M. Izbrannye trudy. Moscow, 1935.
Holden, J., and J. Priestley. Dykhanie. Moscow-Leningrad, 1937. (Translated from English.)
Marshak, M. E. Reguliatsiia dykhaniia u cheloveka. Moscow, 1961.
Fiziologiia cheloveka. Moscow, 1966.
Comroe, J. H. Physiology of Respiration. Chicago, 1966.
Dejours, P. Respiration. Oxford, 1966.L. L. SHIKPlants. Respiration is characteristic of all plant organs, tissues, and cells. The intensity of respiration may be judged by measuring either the quantity of CO₂ eliminated by the tissue or the quantity of O₂ absorbed. Young, rapidly growing plant organs and tissues have higher rates of respiration than older organs and tissues. The highest rate of respiration occurs in the reproductive organs. The leaves are second in rate of respiration, and the rate of respiration of stalks and roots is lower than that of the leaves. Plants that endure shade have a lower rate of respiration than those that require light. A higher rate of respiration is characteristic of high-altitude plants, which have adapted to a decreased partial pressure of O₂ Fungi and bacteria have very high rates of respiration. With increases in temperature, the rate of respiration is roughly doubled or tripled for each 10°C (this phenomenon ceases at 45°-50°C). In the tissues of dormant plant organs (buds of deciduous trees and needles of conifers) respiration continues at sharply reduced rates, even during heavy frosts.
Respiration is stimulated by mechanical and chemical irritants (for example, wounds, certain toxins, and narcotics). During the development of the plant and its organs, respiration varies with lawlike regularity. Dry (dormant) seeds have a very low rate of respiration. With the swelling and subsequent sprouting of seeds, the rate of respiration increases hundreds and thousands of times. At the end of the plant’s period of active growth, the rate of respiration of the tissues decreases as a result of the aging of the protoplasm. During the ripening of seeds and fruits the rate of respiration decreases.
According to the theory of the Soviet biochemist, A. N. Bakh, the process of respiration (the oxidation of carbohydrates, fats, and proteins) occurs by means of the oxidation system of the cells in two stages. First, the oxygen in the air is activated by means of its addition to unsaturated compounds (oxygenases), which are capable of being spontaneously oxidized to form peroxides. Subsequently, the peroxides are activated, releasing atomic oxygen, which is capable of oxidizing organic substances that are not readily oxidized.
According to the theory of dehydrogenation of the Russian botanist V. I. Palladin, the most important link in respiration is the activation of the hydrogen of the substrate, which is accomplished by dehydrogenases. A necessary participant in the complex chain of respiratory processes is water, whose hydrogen is used in addition to the hydrogen in the substrate to reduce the self-oxidizing compounds—the so-called respiratory pigments. During respiration carbon dioxide is formed anaerobically—that is, without the participation of O₂ from the air. Oxygen from the air is used to oxidize respiratory chromogens, which are converted into respiratory pigments.
The theory of plant respiration was further developed through the research of the Soviet botanist S. P. Kostychev, who asserted that the first stages of aerobic respiration are analogous to the respiratory processes that are characteristic of anaerobes. The transformations of the intermediate products formed in the early stages of aerobic respiration may proceed, according to Kostychev, with the participation of O₂, which is characteristic of aerobes. In anaerobes, however, the transformation of intermediate products of respiration proceeds without the participation of molecular O₂.
According to present-day concepts, the process of oxidation, which is the chemical basis of respiration, involves the loss of an electron by a substance. The capacity to take on or give up electrons is a function of the oxidation potential of the compound. Oxygen has the highest oxidation potential and therefore, the maximum capacity to take on electrons. However, the oxidation potential of O₂ differs sharply from that of the respiratory substrate. For this reason, specific compounds play the role of intermediate carriers of electrons from the respiratory substrate to the oxygen. Alternately oxidized and reduced, the carriers make up the system of electron transfer. In taking on an electron from a less oxidized component, a carrier is reduced, and in giving up the electron to the next with a higher potential, the carrier is oxidized. Thus, an electron is transferred from one link in the respiratory chain to another. The final stage of respiration is the transfer of the electron to oxygen.
All these processes (activation of oxygen and hydrogen and electron transfer along the respiratory chain to oxygen) occur primarily in the mitochondria, as a result of the activity of a ramified system -of oxidation-reduction enzymes (cytochromes). Along the chain to oxygen, the electrons, which are mobilized primarily from molecules of organic substances, gradually release the energy contained in them, which is stored by the cells in the form of chemical compounds, chiefly ATP.
Because of the perfect mechanisms of energy storage and use, the processes of energy exchange in the cell proceed at a very high efficiency, as yet unattained in technology. The biological role of respiration is not exhausted with the use of the energy contained in the oxidized organic molecule. During the oxidative conversions of organic substances, active intermediate compounds are formed—metabolites, which the living cell uses to synthesize components of its protoplasm and to form enzymes. These essential processes give respiration its central role in the complex of metabolic processes of the living cell. In respiration the processes of the metabolism of proteins, nucleic acids, carbohydrates, fats, and other components of protoplasm intersect and are interconnected.

REFERENCES

Kostychev, S. P. Fiziologiia rastenii, 3rd ed., vol. 1. Moscow-Leningrad, 1937.
Bakh, A. N. Sobr. trudovpo khimii khimii i hiokhimii. Moscow, 1950.
Tauson, V. O. Osnovnye polozheniia rastitel’noi bioenergetiki. Moscow-Leningrad, 1950.
James, W. O. Dykhanie rastenii. Moscow, 1956. (Translated from English.)
Palladin, V. I. hbrannye trudy. Moscow, 1960.
Mikhlin, D. M. Biokhimiia kletochnogo dykhaniia. Moscow, 1960.
Szent-Gyorgyi, A. Bioenergetika. Moscow, 1960. (Translated from English.)
Rubin, B. A., and M. E. Ladygina. Enzimologiia i biologiia dykhaniia rastenii. Moscow, 1966.
Racker, E. Bioenergeticheskie mekhanizmy. Moscow, 1967. (Translated from English.)
Rubin, B. A. Kurs fiziologii rastenii, 3rd ed. Moscow, 1971.
Kretovich, V. L. Osnovy biokhimii rastenii. Moscow, 1971.

B. A. RUBIN

respiration

[‚res·pə′rā·shən] (physiology) The processes by which tissues and organisms exchange gases with their environment. The act of breathing with the lungs, consisting of inspiration and expiration.

respiration

1. the process in living organisms of taking in oxygen from the surroundings and giving out carbon dioxide (external respiration). In terrestrial animals this is effected by breathing air 2. the chemical breakdown of complex organic substances, such as carbohydrates and fats, that takes place in the cells and tissues of animals and plants, during which energy is released and carbon dioxide produced (internal respiration)
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respiration

[res″pĭ-ra´shun] 1. the exchange of oxygen" >oxygen and carbon dioxide" >carbon dioxide between the atmosphere and the body cells, including inhalation and exhalation, diffusion of oxygen from the pulmonary alveoli to the blood and of carbon dioxide from the blood to the alveoli, followed by the transport of oxygen to and carbon dioxide from the body cells. See also ventilation (def. 2) and see Plates.2. the metabolic processes by which living cells break down carbohydrates, amino acids, and fats to produce energy in the form of adenosine triphosphate (ATP); called also cell respiration.The Respiratory Sequence. The sequence of the respiration process begins as air enters the corridors of the nose or mouth, where it is warmed and moistened. The air then passes through the pharynx, larynx, and trachea and into the bronchi.

The bronchi branch in the lungs into smaller and smaller bronchioles, ending in clusters of tiny air sacs called alveoli" >alveoli; there are 750 million alveoli in the lungs. The blood flows through the lungs in the pulmonary circulation" >pulmonary circulation. Through the thin membrane of the network of capillaries around the alveoli, the air and the blood exchange oxygen and carbon dioxide. The carbon dioxide molecules migrate from the erythrocytes in the capillaries through the porous membrane into the air in the alveoli, while the oxygen molecules cross from the air into the red blood cells.
The erythrocytes proceed through the circulatory system, carrying the oxygen in loose combination with hemoglobin and giving it up to the body cells that need it. In cellular respiration the blood cells release oxygen and pick up carbon dioxide. The lungs dispose of the carbon dioxide, left there by the red blood cells, in the process of breathing. With each breath, about one-sixth of the air in the lungs is exchanged for new air.Breathing. The lungs inflate and deflate 16 to 20 times per minute in adults, 12 to 20 per minute in teenagers, 20 to 30 per minute in children 2 to 12 years old, and 30 to 50 per minute in newborns. Their elastic tissue allows them to expand and contract like a bellows worked by the diaphragm and the intercostal muscles. The diaphragm contracts, flattening itself downward, and thus enlarges the thoracic cavity. At the same time the ribs are pulled up and outward by the action of the narrow but powerful intercostal muscles that expand and contract the rib cage. As the chest expands, the air flows in. Exhalation occurs when the respiratory muscles relax and the chest returns automatically to its minimum size, expelling the air (see also lung).Automatic Breathing Controls. The automatic control of breathing stems from poorly defined areas known as the centers" >respiratory centers, located in the medulla oblongata and pons. From there, impulses are sent down the spinal cord to the nerves that control the diaphragm, and to the intercostal muscles. Chemical and reflex signals control these nerve centers. (See hering-breuer reflexes.)
The chemical controls of breathing are mainly dependent on the level of carbon dioxide in the blood. The response is so sensitive that if the carbon dioxide level increases two-tenths of 1 per cent, the respiratory rate increases automatically to double the amount of air taken in, until the excess of carbon dioxide is eliminated. It is not lack of oxygen but excess of carbon dioxide that causes this instant and powerful reaction.
The tension" >carbon dioxide tension (Pco₂), of arterial blood normally is 35 to 45 mm Hg. When the Pco₂ increases, the respiratory centers are stimulated and breathing becomes more rapid; conversely, decrease of the Pco₂ slows the rate of respiration. The Pco₂ acts both directly on the respiratory centers and on the carotid and aortic bodies, chemoreceptors that are responsive to changes in blood Pco₂, Po₂, and pH (see also blood gas analysis).Protective Respiratory Mechanisms. The lungs are constantly exposed to the surrounding atmosphere. Twenty times a minute, more or less, they take in a gaseous mixture, along with whatever foreign particles happen to be suspended in it and at whatever temperature it may be. To compensate, the lungs have some remarkable protective devices.

On its way through the nasal passage, the cold air from outside is preheated by a large supply of blood, which gives off warmth through the thin mucous membrane that lines the respiratory tract. This same mucous lining is always moist, and dry air picks up moisture as it passes.
Dust, soot, and bacteria are filtered out by a barrier of cilia, tiny hairlike processes that line the passageways of the respiratory tract. The cilia trap not only foreign particles but also mucus produced by the respiratory passages themselves. Since the movement of the cilia is always toward the outside, they move the interfering matter upward, away from the delicate lung tissues, so that it can be expectorated or swallowed. Particles that are too large for the cilia to dispose of usually stimulate a sneeze or a cough, which forcibly expels them. Sneezing and coughing are reflex acts in response to stimulation of nerve endings in the respiratory passages. The stimulus for a cough comes from the air passages in the throat; for a sneeze, from those in the nose.abdominal respiration inspiration accomplished mainly by the diaphragm.aerobic respiration oxidative transformation of certain substrates into high-energy chemical compounds; see also adenosine triphosphate.artificial respiration see artificial respiration.Biot's respiration breathing characterized by irregular periods of apnea alternating with periods in which four or five breaths of identical depth are taken; seen in patients with increased intracranial pressure associated with spinal meningitis and other central nervous system disorders.cell respiration respiration (def. 2).Cheyne-Stokes respiration see cheyne-stokes respiration.cogwheel respiration breathing with jerky inhalation.diaphragmatic respiration that performed mainly by the diaphragm.electrophrenic respiration induction of respiration by electric stimulation of the phrenic nerve; see pacemaker" >phrenic pacemaker. Called also diaphragmatic or phrenic pacing.external respiration the exchange of gases between the lungs and the blood.internal respiration the exchange of gases between the body cells and the blood.Kussmaul's respiration a distressing, paroxysmal dyspnea affecting both inspiration and expiration, characterized by increased respiratory rate (above 20 per minute), increased depth of respiration, panting, and labored respiration; seen in diabetic acidosis and coma and renal failure. Called also air hunger.paradoxical respiration see paradoxical respiration.tissue respiration internal respiration.respiration (omaha) in the omaha system, a client problem in the physiologic domain, defined as the exchange of oxygen and carbon dioxide in the body.

res·pi·ra·tion

(res'pi-rā'shŭn), 1. A fundamental process of life, characteristic of both plants and animals, in which oxygen is used to oxidize organic fuel molecules, providing a source of energy as well as carbon dioxide and water. In green plants, photosynthesis is not considered respiration 2. Synonym(s): ventilation (2) [L. respiratio, fr. respiro, pp. -atus, to exhale, breathe]

respiration

(rĕs′pə-rā′shən)n.1. a. The action or process of inhaling and exhaling; breathing. Also called ventilation.b. An act of inhaling and exhaling; a breath.2. The action or process by which an organism without lungs, such as a fish or plant, exchanges gases with its environment.3. a. The oxidative process occurring within living cells by which the chemical energy of organic molecules is converted in a series of metabolic steps into usable energy in the form of ATP, involving the consumption of oxygen and the production of carbon dioxide and water as byproducts.b. Any of various analogous metabolic processes by which certain organisms, such as anaerobic bacteria and some fungi, obtain energy from organic molecules without consuming oxygen.

res′pi·ra′tion·al adj.

respiration

Breathing; to inhale and exhale; the exchange of gases between the external environment and an organism's cells. See Anaerobic respiration, Cellular respiration, Cheyne-Stokes respiration.

res·pi·ra·tion

(res'pir-ā'shŭn) 1. A fundamental process of life, characteristic of both plants and animals, in which oxygen is used to oxidize organic fuel molecules, providing a source of energy as well as carbon dioxide and water. In green plants, photosynthesis is not considered respiration. 2. Synonym(s): ventilation (2) . [L. respiratio, fr. respiro, pp. -atus, to exhale, breathe]

respiration

(res?pi-ra'shon ) [L. respiratio, breathing] 1. The interchange of gases between an organism and the medium in which it lives.

MUSCLES OF RESPIRATION2. The act of breathing (inhaling and exhaling) during which the lungs are provided with air through inhaling and the carbon dioxide is removed through exhaling. Normal respiratory exchange of oxygen and carbon dioxide in the lungs is impossible unless the pulmonary tissue is adequately perfused with blood. See: lung; ventilation; illustration

abdominal respiration

Respiration in which chiefly the diaphragm exerts itself while the chest wall muscles are nearly at rest; used in normal, quiet breathing, and in pathological conditions such as pleurisy, pericarditis, and rib fracture. Synonym: belly breathing; diaphragmatic respiration

absent respiration

Respiration in which respiratory sounds are suppressed or absent.

accelerated respiration

Tachypnea.

aerobic respiration

Cellular respiration in which oxygen is used in the production of energy.

amphoric respiration

Respiration having amphoric resonance. See: amphoric resonance

anaerobic respiration

The release of energy from the reduction of metals (such as iron, manganese, or sulfur) by cells or organisms that do not use oxygen as their primary energy source.

apneustic respiration

Breathing marked by prolonged inspiration unrelieved by attempts to exhale. It is seen in patients who have had the upper part of the pons of the brain removed or damaged.

artificial respiration

Maintenance of respiratory movement by artificial means, such as rescue breathing, bag mask, pocket mask, automatic transport ventilator, manual transport ventilator, or a flow-restricted oxygen-powered ventilation device. See: cardiopulmonary resuscitation

Biot respiration

Biot breathing.

Bouchut respiration

See: Bouchut respiration

cell respiration

The gradual breakdown of food molecules in the presence of oxygen within cells, resulting in the formation of carbon dioxide and water and the release of energy in the forms of adenosine triphosphate and heat. In many intermediary reactions, substances other than oxygen act as oxidizing agents (hydrogen or electron acceptors). Reactions are catalyzed by respiratory enzymes, which include the flavoproteins, cytochromes, and other enzymes. Certain vitamins (nicotinamide, riboflavin, thiamine, pyridoxine, and pantothenic acid) are essential in the formation of components of various intracellular enzyme systems.

Cheyne-Stokes respiration

See: Cheyne-Stokes respiration

cogwheel respiration

Interrupted respiration.

costal respiration

Respiration in which the chest cavity expands by raising the ribs.

cutaneous respiration

The transpiration of gases through the skin.

decreased respiration

Respiration at less than a normal rate for the individual's age. In adults, it is a respiratory rate of less than 12 breaths per minute. Slower than normal respiratory rates occur after opiate or sedative use, during sleep, in coma, and other conditions and may result in respiratory failure or carbon dioxide retention. Synonym: slow respiration

diaphragmatic respiration

Abdominal respiration.

direct respiration

Respiration in which an organism, such as a one-celled ameba, secures its oxygen and gives up carbon dioxide directly to the surrounding medium.

electrophrenic respiration

Radiofrequency electrophrenic respiration.

external respiration

The exchange of gases in the lungs. Oxygen diffuses from the air to the blood, and carbon dioxide diffuses from the blood to the air. See: gas exchange

fetal respiration

Gas exchange in the placenta between the fetal and maternal blood. Synonym: placental respiration

forced respiration

Voluntary hyperpnea.

internal respiration

The exchange of gases in body tissues. Oxygen diffuses from the blood to the cells, and carbon dioxide diffuses from the cells to the blood. Oxygen is carried in combination with hemoglobin. Oxyhemoglobin gives arterial blood its red color; reduced hemoglobin gives venous blood its dark red color. Most carbon dioxide is carried in the blood as bicarbonate ions; a small amount is bonded to hemoglobin. Normally the partial pressure of oxygen in the blood is 75 to 100 mm Hg, depending on age; for carbon dioxide it is 35 to 45 mm Hg. Synonym: tissue respiration See: gas exchange

interrupted respiration

Respiration in which inspiratory or expiratory sounds are not continuous. Synonym: cogwheel respiration

intrauterine respiration

Respiration by the fetus before birth. See: fetal respiration

Kussmaul respiration

See: Kussmaul, Adolph

labored respiration

Respiration that involves active participation of accessory inspiratory and expiratory muscles; dyspnea.

mitochondrial respiration

The stages of cell respiration (citric acid cycle and cytochrome transport system) that take place in the mitochondria. Water is formed from oxygen and hydrogen ions, and energy is released. See: cell respiration

paradoxical respiration

1. Respiration occurring in patients with chest trauma and multiple rib fractures in which a portion of the chest wall sinks inward with each spontaneous inspiratory effort.2. A condition seen in paralysis of the diaphragm in which the diaphragm ascends during inspiration.

periodic respiration

Periodic breathing.

placental respiration

Fetal respiration.

radiofrequency electrophrenic respiration

A method of stimulating respiration in cases of respiratory paralysis from spinal cord injury at the cervical level. Intermittent electrical stimuli to the phrenic nerves are supplied by a radiofrequency transmitter implanted subcutaneously. The diaphragmatic muscles contract in response to these stimuli.

slow respiration

Decreased respiration.

stertorous respiration

Stertor.

stridulous respiration

Respiration marked by high-pitched crowing or barking sound heard on inspiration, caused by an obstruction near the glottis or in the respiratory passageway.

thoracic respiration

Respiration performed entirely by expansion of the chest when the abdomen does not move. It is seen when the peritoneum or diaphragm is inflamed, when the abdominal cavity is restricted by tight bandages or clothes, or during abdominal surgery. See: Thoracic Spine and Rib Cage Breathing

tissue respiration

Internal respiration.

vicarious respiration

Increased respiration in one lung when respiration in the other is lessened or abolished.

respiration

1. Breathing. 2. The whole process by which oxygen is transferred from the atmosphere to the body cells and carbon dioxide is moved from the cells to the atmosphere. Respiration is vital to life and cessation for more than a few minutes is fatal. See also CHEYNE-STOKES RESPIRATION.

respiration

a process by which gaseous exchange (oxygen and carbon dioxide) takes place between an organism and the surrounding medium. See AERIAL RESPIRATION, AQUATIC RESPIRATION, BREATHING.
a form of CATABOLISM that takes place in all living cells. See ANAEROBIC RESPIRATION, AEROBIC RESPIRATION.

Respiration

Respiration is the process by which nutrients (specifically sugar, or glucose) and oxygen are taken in to a cell; chemical reactions take place; energy is produce and stored; and carbon dioxide and wastes are given off.Mentioned in: Pellagra

res·pi·ra·tion

(res'pir-ā'shŭn) 1. Fundamental process of life, characteristic of both plants and animals, in which oxygen is used to oxidize organic fuel molecules, providing a source of energy as well as carbon dioxide and water. In green plants, photosynthesis is not considered respiration 2. Synonym(s): ventilation (2) . [L. respiratio, fr. respiro, pp. -atus, to exhale, breathe]

Patient discussion about respiration

Q. Help her to breathe. My sixteen year old cousin (girl) who is wondering if she is suffering from asthma, anxiety or both. She is thin, healthy girl and have been very worried She have asthma and have been thinking about it constantly. When she exercise, she get more out of breath, more worn out, and her heart beats faster than other people. Sometimes her chest hurts, but people tell me that is from my chest muscles being worked. She get a little dizzy also. When she go to bed at night sometimes it seems hard to breathe. She can take a deep breath and everything but it seems hard or something. I know there isn't anything wrong with my heart because she had an EKG done recently and chest x-rays. That was fine. When it is hot humid and muggy outside she find it hard to breath. Do you think she have asthma. She don't have any coughing or any known wheezing. Could thinking about every breath she take seem like she have asthma? She really want to know and me too, what is going on! Please help her to breathe!!!!A. PS--alcohol and cigarettes can cause this problem to(drugs)mrfoot56.

Q. What causes bad breath? I have bad breath for a long time. What causes it?A. Here are some causes of bad breath:
A Dry mouth- Saliva helps cleanse and moisten your mouth. A dry mouth enables dead cells to accumulate on your tongue, gums and cheeks. These cells then decompose and cause odor. Dry mouth naturally occurs during sleep. It's what causes "morning breath." Dry mouth is even more of a problem if you sleep with your mouth open. Some medications as well as smoking can lead to a chronic dry mouth, as can a problem with your salivary glands.
Some Diseases can also cause bad breath- Chronic lung infections and lung abscesses can produce very foul-smelling breath. Other illnesses, such as some cancers and certain metabolic disorders, can cause a distinctive breath odor. Kidney failure can cause a urine-like odor, and liver failure may cause an odor described as "fishy." People with uncontrolled diabetes often have a fruity breath odor. Chronic reflux of stomach acids from your stomach (gastroesophageal reflux disease, or GERD)

Q. How to get rid of bad breath? My wife complains that I have bad breath. How can I get rid of it?A. Consider that candida infection can make your breath worse. You might try cutting down on sugar and carbs.
"Bad breath can also be caused by a candida (yeast infection), you may have a constant white furry tongue. Look at cutting down your intake of sugars and processed foods, as well as those containing yeast. - Search for Anti-Candida diet on a search engine for more info"
http://www.wikihow.com/Fix-Bad-Breath-on-the-Spot

More discussions about respiration

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Animal Respiration

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REFERENCES

REFERENCES

respiration

respiration

respiration

respiration

res·pi·ra·tion

respiration

respiration

res·pi·ra·tion

respiration

abdominal respiration

absent respiration

accelerated respiration

aerobic respiration

amphoric respiration

anaerobic respiration

apneustic respiration

artificial respiration

Biot respiration

Bouchut respiration

cell respiration

Cheyne-Stokes respiration

cogwheel respiration

costal respiration

cutaneous respiration

decreased respiration

diaphragmatic respiration

direct respiration

electrophrenic respiration

external respiration

fetal respiration

forced respiration

internal respiration

interrupted respiration

intrauterine respiration

Kussmaul respiration

labored respiration

mitochondrial respiration

paradoxical respiration

periodic respiration

placental respiration

radiofrequency electrophrenic respiration

slow respiration

stertorous respiration

stridulous respiration

thoracic respiration

tissue respiration

vicarious respiration

respiration

respiration

Respiration

res·pi·ra·tion

Patient discussion about respiration

Respiration

respiration

Synonyms for respiration

noun the act or process of breathing

Synonyms

Synonyms for respiration

noun the metabolic processes whereby certain organisms obtain energy from organic molecules

Synonyms

Related Words

noun a single complete act of breathing in and out

Related Words

noun the bodily process of inhalation and exhalation