The control of ventilation is the

physiological Physiology (; ) is the science, scientific study of function (biology), functions and mechanism (biology), mechanisms in a life, living system. As a branches of science, subdiscipline of biology, physiology focuses on how organisms, organ syst ...

mechanisms involved in the control of

breathing Breathing (spiration or ventilation) is the rhythmical process of moving air into ( inhalation) and out of ( exhalation) the lungs to facilitate gas exchange with the internal environment, mostly to flush out carbon dioxide and bring in oxy ...

, which is the movement of air into and out of the lungs. Ventilation facilitates respiration. Respiration refers to the utilization of

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

and balancing of

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

by the body as a whole, or by individual cells in

cellular respiration Cellular respiration is the process of oxidizing biological fuels using an inorganic electron acceptor, such as oxygen, to drive production of adenosine triphosphate (ATP), which stores chemical energy in a biologically accessible form. Cell ...

. The most important function of breathing is the supplying of oxygen to the body and balancing of the carbon dioxide levels. Under most conditions, the partial pressure of carbon dioxide (PCO₂), or concentration of carbon dioxide, controls the

respiratory rate The respiratory rate is the rate at which breathing occurs; it is set and controlled by the respiratory center of the brain. A person's respiratory rate is usually measured in breaths per minute. Measurement The respiratory rate in humans is mea ...

. The

peripheral chemoreceptor Peripheral chemoreceptors (of the carotid and aortic bodies) are so named because they are sensory extensions of the peripheral nervous system into blood vessels where they detect changes in chemical concentrations. As transducers of patterns of ...

s that detect changes in the levels of oxygen and carbon dioxide are located in the

arterial An artery () is a blood vessel in humans and most other animals that takes oxygenated blood away from the heart in the systemic circulation to one or more parts of the body. Exceptions that carry deoxygenated blood are the pulmonary arteries in ...

aortic bodies and the carotid bodies.

Central chemoreceptors A central chemoreceptor is a chemoreceptor sensitive to the pH of its environment. Central chemoreceptors are located on the ventrolateral medulla oblongata, medullary surface in vicinity of the exit of CN IX and CN X in the central nervous syste ...

are primarily sensitive to changes in the pH of the

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood is com ...

, (resulting from changes in the levels of carbon dioxide) and they are located on the

medulla oblongata The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involun ...

near to the medullar respiratory groups of the

respiratory center The respiratory center is located in the medulla oblongata and pons, in the brainstem. The respiratory center is made up of three major respiratory groups of neurons, two in the medulla and one in the pons. In the medulla they are the dorsal ...

. Information from the peripheral chemoreceptors is conveyed along nerves to the respiratory groups of the respiratory center. There are four respiratory groups, two in the medulla and two in the

pons The pons (from Latin , "bridge") is part of the brainstem that in humans and other mammals, lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum. The pons is also called the pons Varolii ("bridge of ...

. The two groups in the pons are known as the pontine respiratory group. # Dorsal respiratory group – in the medulla # Ventral respiratory group – in the medulla # Pneumotaxic center – various nuclei of the pons # Apneustic center – nucleus of the pons From the respiratory center, the

muscles of respiration The muscles of respiration are the muscles that contribute to inhalation and exhalation, by aiding in the expansion and contraction of the thoracic cavity. The diaphragm and, to a lesser extent, the intercostal muscles drive respiration during ...

, in particular the diaphragm,Tortora, G. J. and Derrickson, B. H., (2009). Principles of Anatomy and Physiology – Maintenance and continuity of the human body. 12th Edition. Danvers: Wiley are activated to cause air to move in and out of the lungs.

Control of respiratory rhythm

Ventilatory pattern

Breathing is normally an unconscious, involuntary, automatic process. The pattern of motor stimuli during breathing can be divided into an

inhalation Inhalation (or inspiration) happens when air or other gases enter the lungs. Inhalation of air Inhalation of air, as part of the cycle of breathing, is a vital process for all human life. The process is autonomic (though there are exceptions ...

stage and an

exhalation Exhalation (or expiration) is the flow of the breathing, breath out of an organism. In animals, it is the movement of air from the lungs out of the airways, to the external environment during breathing. This happens due to elastic properties of ...

stage.

Inhalation Inhalation (or inspiration) happens when air or other gases enter the lungs. Inhalation of air Inhalation of air, as part of the cycle of breathing, is a vital process for all human life. The process is autonomic (though there are exceptions ...

shows a sudden, ramped increase in motor discharge to the respiratory muscles (and the pharyngeal constrictor muscles). Before the end of inhalation, there is a decline in, and end of motor discharge.

Exhalation Exhalation (or expiration) is the flow of the breathing, breath out of an organism. In animals, it is the movement of air from the lungs out of the airways, to the external environment during breathing. This happens due to elastic properties of ...

is usually silent, except at high

s. The respiratory centre in the medulla and pons of the brainstem controls the rate and depth of respiration, (the respiratory rhythm), through various inputs. These include signals from the peripheral chemoreceptors and central chemoreceptors; from the vagus nerve and glossopharyngeal nerve carrying input from the pulmonary stretch receptors, and other mechanoreceptors in the

lung The lungs are the primary Organ (biology), organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the Vertebral column, backbone on either side of the heart. Their ...

s. as well as signals from the

cerebral cortex The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. It is the largest site of Neuron, neural integration in the central nervous system, and plays ...

and

hypothalamus The hypothalamus (: hypothalami; ) is a small part of the vertebrate brain that contains a number of nucleus (neuroanatomy), nuclei with a variety of functions. One of the most important functions is to link the nervous system to the endocrin ...

. * Medulla ** ventral respiratory group (includes the pre-Bötzinger complex). The ventral respiratory group controls voluntary forced exhalation and acts to increase the force of inhalation. Regulates rhythm of inhalation and exhalation. ** dorsal respiratory group (

solitary nucleus The solitary nucleus (SN) (nucleus of the solitary tract, nucleus solitarius, or nucleus tractus solitarii) is a series of neurons whose cell bodies form a roughly vertical column of grey matter in the medulla oblongata of the brainstem. Their a ...

). The dorsal respiratory group controls mostly movements of inhalation and their timing. * Pons ** pneumotaxic center. *** Coordinates speed of inhalation and exhalation *** Sends inhibitory impulses to the inspiratory area *** Involved in fine tuning of respiration rate. ** apneustic center *** Coordinates speed of inhalation and exhalation. *** Sends stimulatory impulses to the inspiratory area – activates and prolongs inhalations *** Overridden by pneumotaxic control from the apneustic area to end inhalation

Control of ventilatory pattern

Ventilation is normally unconscious and automatic, but can be overridden by conscious alternative patterns. Thus the emotions can cause yawning, laughing, sighing (etc.), social communication causes speech, song and whistling, while entirely voluntary overrides are used to blow out candles, and breath holding (for instance, to swim underwater).

Hyperventilation Hyperventilation is irregular breathing that occurs when the rate or tidal volume of breathing eliminates more carbon dioxide than the body can produce. This leads to hypocapnia, a reduced concentration of carbon dioxide dissolved in the blo ...

may be entirely voluntary or in response to emotional agitation or anxiety, when it can cause the distressing

hyperventilation syndrome Hyperventilation syndrome (HVS), also known as chronic hyperventilation syndrome (CHVS), dysfunctional breathing hyperventilation syndrome, cryptotetany, spasmophilia, latent tetany, and central neuronal hyper excitability syndrome (NHS), is a r ...

. The voluntary control can also influence other functions such as the

heart rate Heart rate is the frequency of the cardiac cycle, heartbeat measured by the number of contractions of the heart per minute (''beats per minute'', or bpm). The heart rate varies according to the body's Human body, physical needs, including the nee ...

as in

yoga Yoga (UK: , US: ; 'yoga' ; ) is a group of physical, mental, and spiritual practices or disciplines that originated with its own philosophy in ancient India, aimed at controlling body and mind to attain various salvation goals, as pra ...

practices and

meditation Meditation is a practice in which an individual uses a technique to train attention and awareness and detach from reflexive, "discursive thinking", achieving a mentally clear and emotionally calm and stable state, while not judging the meditat ...

. The ventilatory pattern is also temporarily modified by complex reflexes such as sneezing, straining, burping, coughing and vomiting.

Determinants of ventilatory rate

Ventilatory rate ( respiratory minute volume) is tightly controlled and determined primarily by blood levels of

as determined by

metabolic rate Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the co ...

. Blood levels of

become important in hypoxia. These levels are sensed by

central chemoreceptors A central chemoreceptor is a chemoreceptor sensitive to the pH of its environment. Central chemoreceptors are located on the ventrolateral medulla oblongata, medullary surface in vicinity of the exit of CN IX and CN X in the central nervous syste ...

on the surface of the

for decreased pH (indirectly from the increase of carbon dioxide in

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless Extracellular fluid#Transcellular fluid, transcellular body fluid found within the meninges, meningeal tissue that surrounds the vertebrate brain and spinal cord, and in the ventricular system, ven ...

), and the peripheral chemoreceptors in the arterial blood for oxygen and carbon dioxide. Afferent neurons from the peripheral chemoreceptors are via the

glossopharyngeal nerve The glossopharyngeal nerve (), also known as the ninth cranial nerve, cranial nerve IX, or simply CN IX, is a cranial nerve that exits the brainstem from the sides of the upper Medulla oblongata, medulla, just anterior (closer to the nose) to t ...

(CN IX) and the

vagus nerve The vagus nerve, also known as the tenth cranial nerve (CN X), plays a crucial role in the autonomic nervous system, which is responsible for regulating involuntary functions within the human body. This nerve carries both sensory and motor fibe ...

(CN X). The concentration of

(CO₂) rises in the blood when the metabolic use of oxygen (O₂), and the production of CO₂ is increased during, for example, exercise. The CO₂ in the blood is transported largely as bicarbonate (HCO₃⁻) ions, by conversion first to

carbonic acid Carbonic acid is a chemical compound with the chemical formula . The molecule rapidly converts to water and carbon dioxide in the presence of water. However, in the absence of water, it is quite stable at room temperature. The interconversion ...

(H₂CO₃), by the enzyme

carbonic anhydrase The carbonic anhydrases (or carbonate dehydratases) () form a family of enzymes that catalyst, catalyze the interconversion between carbon dioxide and water and the Dissociation (chemistry), dissociated ions of carbonic acid (i.e. bicarbonate a ...

, and then by disassociation of this acid to H⁺ and HCO₃⁻. Build-up of CO₂ therefore causes an equivalent build-up of the disassociated hydrogen ions, which, by definition, decreases the pH of the blood. The pH sensors on the brain stem immediately respond to this fall in pH, causing the respiratory center to increase the rate and depth of

. The consequence is that the

partial pressure In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. The total pressure of an ideal g ...

of CO (P_CO₂) does not change from rest going into exercise. During very short-term bouts of intense exercise the release of lactic acid into the blood by the exercising muscles causes a fall in the blood plasma pH, independently of the rise in the P_CO₂, and this will stimulate pulmonary ventilation sufficiently to keep the blood pH constant at the expense of a lowered P_CO₂. Mechanical stimulation of the lungs can trigger certain reflexes as discovered in animal studies. In humans, these seem to be more important in neonates and ventilated patients, but of little relevance in health. The tone of respiratory muscle is believed to be modulated by

muscle spindle Muscle spindles are stretch receptors within the body of a skeletal muscle that primarily detect changes in the length of the muscle. They convey length information to the central nervous system via afferent nerve fibers. This information can be ...

s via a reflex arc involving the spinal cord. Drugs can greatly influence the rate of respiration.

Opioids Opioids are a class of Drug, drugs that derive from, or mimic, natural substances found in the Papaver somniferum, opium poppy plant. Opioids work on opioid receptors in the brain and other organs to produce a variety of morphine-like effects, ...

and

anesthetic An anesthetic (American English) or anaesthetic (British English; see spelling differences) is a drug used to induce anesthesia ⁠— ⁠in other words, to result in a temporary loss of sensation or awareness. They may be divided into t ...

s tend to depress ventilation, by decreasing the normal response to raised

levels in the arterial blood. Stimulants such as

amphetamines Substituted amphetamines, or simply amphetamines, are a chemical class, class of compounds based upon the amphetamine structure; it includes all derivative (chemistry), derivative compounds which are formed by replacing, or substitution reacti ...

can cause

hyperventilation Hyperventilation is irregular breathing that occurs when the rate or tidal volume of breathing eliminates more carbon dioxide than the body can produce. This leads to hypocapnia, a reduced concentration of carbon dioxide dissolved in the blo ...

Pregnancy Pregnancy is the time during which one or more offspring gestation, gestates inside a woman's uterus. A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Conception (biology), Conception usually occurs ...

tends to increase ventilation (lowering plasma carbon dioxide tension below normal values). This is due to increased

progesterone Progesterone (; P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the ma ...

levels and results in enhanced gas exchange in the

placenta The placenta (: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas, and waste exchange between ...

Feedback control

Receptor Receptor may refer to: * Sensory receptor, in physiology, any neurite structure that, on receiving environmental stimuli, produces an informative nerve impulse *Receptor (biochemistry), in biochemistry, a protein molecule that receives and respond ...

s play important roles in the regulation of respiration and include the central and peripheral chemoreceptors, and

pulmonary stretch receptors Pulmonary stretch receptors are mechanoreceptors found in the lungs. When the lung expands, the receptors initiate the Hering-Breuer reflex, which reduces the respiratory rate. This signal is transmitted by vagus nerve. Increased firing from th ...

, a type of

mechanoreceptor A mechanoreceptor, also called mechanoceptor, is a sensory receptor that responds to mechanical pressure or distortion. Mechanoreceptors are located on sensory neurons that convert mechanical pressure into action potential, electrical signals tha ...

. *

of the central nervous system, located on the ventrolateral medullary surface, are sensitive to the pH of their environment.Coates EL, Li A, Nattie EE. Widespread sites of brain stem ventilatory chemoreceptors. J Appl Physiol. 75(1):5–14, 1984.Cordovez JM, Clausen C, Moore LC, Solomon, IC. A mathematical model of pH(i) regulation in central CO₂ chemoreception. Adv Exp Med Biol. 605:306–311, 2008. * Peripheral chemoreceptors act most importantly to detect variation of the PO2 in the

arterial blood Arterial blood is the oxygenated blood in the circulatory system found in the pulmonary vein, the left chambers of the heart, and in the artery, arteries. It is bright red in color, while venous blood is dark red in color (but looks purple through ...

, in addition to detecting arterial P_CO₂ and pH. *

Mechanoreceptors A mechanoreceptor, also called mechanoceptor, is a sensory receptor that responds to mechanical pressure or distortion. Mechanoreceptors are located on sensory neurons that convert mechanical pressure into electrical signals that, in animals, ar ...

are located in the

airway The respiratory tract is the subdivision of the respiratory system involved with the process of conducting air to the alveoli for the purposes of gas exchange in mammals. The respiratory tract is lined with respiratory epithelium as respiratory ...

s and

parenchyma upright=1.6, Lung parenchyma showing damage due to large subpleural bullae. Parenchyma () is the bulk of functional substance in an animal organ such as the brain or lungs, or a structure such as a tumour. In zoology, it is the tissue that ...

, and are responsible for a variety of reflex responses. These include: ** The Hering-Breuer reflex that terminates inhalation to prevent over inflation of the lungs, and the reflex responses of

coughing A cough is a sudden expulsion of air through the large breathing passages which can help clear them of fluids, irritants, foreign particles and microbes. As a protective reflex, coughing can be repetitive with the cough reflex following three ...

, airway constriction, and

. ** The upper airway receptors are responsible for reflex responses such as,

sneezing A sneeze (also known as sternutation) is a semi-autonomous, convulsive expulsion of air from the lungs through the nose and mouth, usually caused by foreign particles irritating the nasal mucosa. A sneeze expels air forcibly from the mouth a ...

, coughing, closure of

glottis The glottis (: glottises or glottides) is the opening between the vocal folds (the rima glottidis). The glottis is crucial in producing sound from the vocal folds. Etymology From Ancient Greek ''γλωττίς'' (glōttís), derived from ''γ ...

, and

hiccups A hiccup (scientific name singultus, from Latin for "sob, hiccup"; also spelled hiccough) is an involuntary contraction ( myoclonic jerk) of the diaphragm that may repeat several times per minute. The hiccup is an involuntary action involvi ...

. ** The

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

reflex responses include the activation of additional respiratory muscles as compensation, gasping response, hypoventilation, and an increase in breathing frequency and volume. ** The nasopulmonary and nasothoracic

reflex In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus. Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...

es regulate the mechanism of breathing through deepening the inhale. Triggered by the flow of the air, the pressure of the air in the

nose A nose is a sensory organ and respiratory structure in vertebrates. It consists of a nasal cavity inside the head, and an external nose on the face. The external nose houses the nostrils, or nares, a pair of tubes providing airflow through the ...

, and the quality of the air, impulses from the nasal mucosa are transmitted by the trigeminal nerve to the

in the

brainstem The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...

, and the generated response is transmitted to the

bronchi A bronchus ( ; : bronchi, ) is a passage or airway in the lower respiratory tract that conducts air into the lungs. The first or primary bronchi to branch from the trachea at the carina are the right main bronchus and the left main bronchus. Thes ...

, the

intercostal muscles The intercostal muscles comprise many different groups of muscles that run between the ribs, and help form and move the chest wall. The intercostal muscles are mainly involved in the mechanical aspect of breathing by helping expand and shrink th ...

and the diaphragm. ** Head's paradoxical reflex where sudden inflation of the lung causes a transient respiratory effort or gasp.

References

External links

* * Rabbany, Sina Y., "Breathing Coordination", Hofstra Universit

* Webber, Charles L., Jr., Ph.D., Pulmonary Curriculum Function:"Neural Control of Breathing", Stritch School of Medicine, Loyola University-Chicag

{{DEFAULTSORT:Control Of Respiration Respiratory physiology