Breathing

breathventilationrespirationbreathealveolar ventilationbreathing exercisespulmonary ventilationexhalinginhalingrespiratory
Breathing (or ventilation) is the process of moving air into and out of the lungs to facilitate gas exchange with the internal environment, mostly by bringing in oxygen and flushing out carbon dioxide.wikipedia
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Lung

lungspulmonaryright lung
Breathing (or ventilation) is the process of moving air into and out of the lungs to facilitate gas exchange with the internal environment, mostly by bringing in oxygen and flushing out carbon dioxide.
Mammals, reptiles and birds use their different muscles to support and foster breathing.

Atmosphere of Earth

airEarth's atmosphereatmosphere
Breathing (or ventilation) is the process of moving air into and out of the lungs to facilitate gas exchange with the internal environment, mostly by bringing in oxygen and flushing out carbon dioxide.
Air composition, temperature, and atmospheric pressure vary with altitude, and air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth's troposphere and in artificial atmospheres.

Exhalation

expirationexhaleexhaled
The breathing of all vertebrates with lungs consists of repetitive cycles of inhalation and exhalation through a highly branched system of tubes or airways which lead from the nose to the alveoli.
Exhalation (or expiration) is the flow of the breath out of an organism.

Respiratory rate

breathing rateraterate of breathing
The number of respiratory cycles per minute is the breathing or respiratory rate, and is one of the four primary vital signs of life.
The respiratory rate is the rate at which breathing occurs.

Hypoventilation

respiratory depressiondecreased effort to breathedecreased breathing
Over-breathing (hyperventilation) and under-breathing (hypoventilation), which decrease and increase the arterial partial pressure of carbon dioxide respectively, cause a rise in the pH of ECF in the first case, and a lowering of the pH in the second.
Hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate (hypo meaning "below") to perform needed gas exchange.

Oxygen

OO 2 molecular oxygen
Breathing (or ventilation) is the process of moving air into and out of the lungs to facilitate gas exchange with the internal environment, mostly by bringing in oxygen and flushing out carbon dioxide. Under normal conditions the breathing depth and rate is automatically, and unconsciously, controlled by several homeostatic mechanisms which keep the partial pressures of carbon dioxide and oxygen in the arterial blood constant.
He noted that candles burned brighter in the gas and that a mouse was more active and lived longer while breathing it.

Hyperventilation

hyperventilatinghyperventilaterapid breathing
Over-breathing (hyperventilation) and under-breathing (hypoventilation), which decrease and increase the arterial partial pressure of carbon dioxide respectively, cause a rise in the pH of ECF in the first case, and a lowering of the pH in the second.
Hyperventilation occurs when the rate or tidal volume of breathing eliminates more carbon dioxide than the body can produce.

Gas exchange

pulmonary gas exchangegaseous exchangealveolar gas exchange
Breathing (or ventilation) is the process of moving air into and out of the lungs to facilitate gas exchange with the internal environment, mostly by bringing in oxygen and flushing out carbon dioxide.
Air is brought to the alveoli in small doses (called the tidal volume), by breathing in (inhalation) and out (exhalation) through the respiratory airways, a set of relatively narrow and moderately long tubes which start at the nose or mouth and end in the alveoli of the lungs in the chest.

Respiratory tract

airwayupper respiratory tractlower respiratory tract
The breathing of all vertebrates with lungs consists of repetitive cycles of inhalation and exhalation through a highly branched system of tubes or airways which lead from the nose to the alveoli.
The diaphragm is also the main muscle of respiration involved in breathing, and is controlled by the sympathetic nervous system.

Muscles of respiration

respiratory musclesaccessory muscles of respirationmuscle of respiration
During forceful inhalation (Figure on the right) the accessory muscles of inhalation, which connect the ribs and sternum to the cervical vertebrae and base of the skull, in many cases through an intermediary attachment to the clavicles, exaggerate the pump handle and bucket handle movements (see illustrations on the left), bringing about a greater change in the volume of the chest cavity.
The diaphragm and, to a lesser extent, the intercostal muscles drive respiration during quiet breathing.

Hyperpnea

hyperpnoeaheavy breathing
During heavy breathing (hyperpnea) as, for instance, during exercise, exhalation is brought about by relaxation of all the muscles of inhalation, (in the same way as at rest), but, in addition, the abdominal muscles, instead of being passive, now contract strongly causing the rib cage to be pulled downwards (front and sides).
Hyperpnea is increased depth and rate of breathing.

Dead space (physiology)

dead spacedead-space volumedeadspace
A system such as this creates dead space, a volume of air that fills the airways (the dead space) at the end of inhalation, and is breathed out, unchanged, during the next exhalation, never having reached the alveoli.
In other words, not all the air in each breath is available for the exchange of oxygen and carbon dioxide.

Sneeze

sneezingAtchoo!Achoo
It is also used for reflexes such as yawning, coughing and sneezing.
In Europe, principally around the early Middle Ages, it was believed that one's life was in fact tied to one's breath – a belief reflected in the word "expire" (originally meaning "to exhale") gaining the additional meaning of "to come to an end" or "to die".

Medulla oblongata

medullabulbarmedullary
The sensors are, firstly, the central chemoreceptors on the surface of the medulla oblongata of the brain stem which are particularly sensitive to pH as well as the partial pressure of carbon dioxide in the blood and cerebrospinal fluid.
The medulla contains the cardiac, respiratory, vomiting and vasomotor centers and therefore deals with the autonomic functions of breathing, heart rate and blood pressure as well as the sleep wake cycle.

Reflex

reflexesreflex actioninvoluntary action
It is also used for reflexes such as yawning, coughing and sneezing.

Peripheral chemoreceptors

peripheral chemoreceptorperipheralaortic and carotid bodies
The tissues are therefore not exposed to swings in oxygen and carbon dioxide tensions in the blood during the breathing cycle, and the peripheral and central chemoreceptors do not need to "choose" the point in the breathing cycle at which the blood gases need to be measured, and responded to.
Afferent nerves carry signals back from the carotid and aortic bodies to the brainstem, which responds accordingly (e.g. increasing ventilation).

Acid–base homeostasis

acid-base balanceacid-base homeostasisphysiological pH
Keeping the partial pressure of carbon dioxide in the arterial blood unchanged under a wide variety of physiological circumstances, contributes significantly to tight control of the pH of the extracellular fluids (ECF).
This is achieved by changes in the rate and depth of breathing (i.e. by hyperventilation or hypoventilation), which blows off or retains carbon dioxide (and thus carbonic acid) in the blood plasma.

Breathing gas

breathing gasesmixed gasGas
In addition to air, underwater divers practicing technical diving may breathe oxygen-rich, oxygen-depleted or helium-rich breathing gas mixtures.
A breathing gas is a mixture of gaseous chemical elements and compounds used for respiration.

Basal metabolic rate

metabolic ratebasal metabolismBMR
The metabolic rate slows right down.
Some of those processes are breathing, blood circulation, controlling body temperature, cell growth, brain and nerve function, and contraction of muscles.

Homeostasis

homeostaticequilibriumimmunomodulation
Under normal conditions the breathing depth and rate is automatically, and unconsciously, controlled by several homeostatic mechanisms which keep the partial pressures of carbon dioxide and oxygen in the arterial blood constant.
Measurement of the plasma osmolality to give an indication of the water content of the body, relies on the fact that water losses from the body, (through unavoidable water loss through the skin which is not entirely waterproof and therefore always slightly moist, water vapor in the exhaled air, sweating, vomiting, normal feces and especially diarrhea) are all hypotonic, meaning that they are less salty than the body fluids (compare, for instance, the taste of saliva with that of tears.

Thoracic diaphragm

diaphragmdiaphragmatichemidiaphragm
In humans, as in the other mammals, this is achieved primarily through the contraction of the diaphragm, but also by the contraction of the intercostal muscles which pull the rib cage upwards and outwards as shown in the diagrams on the left.
The diaphragm is the main muscle of respiration and functions in breathing.

Chronic obstructive pulmonary disease

emphysemaCOPDpulmonary emphysema
This external manifestation of the use of the accessory muscles of inhalation is sometimes referred to as clavicular breathing, seen especially during asthma attacks and in people with chronic obstructive pulmonary disease.
This can also lead to insufficient ventilation, and eventually low blood oxygen levels.

Inhalation

inspirationinhaledinhale
The breathing of all vertebrates with lungs consists of repetitive cycles of inhalation and exhalation through a highly branched system of tubes or airways which lead from the nose to the alveoli.

Diaphragmatic breathing

deep breathingdiaphragmabdominal breathing
Diaphragmatic breathing causes the abdomen to rhythmically bulge out and fall back.

Shortness of breath

dyspnearespiratory distressdyspnoea
Other breathing disorders include shortness of breath (dyspnea), stridor, apnea, sleep apnea (most commonly obstructive sleep apnea), mouth breathing, and snoring.
Shortness of breath (SOB), also known as dyspnea, is the feeling that one cannot breathe well enough.