the control of breathing.docx

8/10/2019 The control of breathing.docx

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The control of breathingWritten by: Thuy Bui from Manchester University, John Lees from Manchester University,

General introduction: Supply and demand

Ultimately the control of breathing is about supply and demand, where the respiratory system (the supplier)

provides the blood (the road system connecting supplier and consumer) with the O2 required by our cells (the

consumers) to perform aerobic metabolism(at the mitochondria).The respiratory system subsequently then

removes the CO2 bye-product of this process

Normally supply and demand are in equilibrium and the cellular metabolic requirements are met by the

level of O2 delivery and CO2 removal from capillaries, which in turn are in equilibrium with the rate of delivery

and removal at the lungs

During different levels of metabolic activity however, the balance may be shifted. To cope with this variation in

demand, many homeostatic mechanismsfunction in maintaining optimal levels of respiration. The overall

result of these various feedback systems is a tight control of respiration at both thelocal(the lungs, the

distribution centre if you will) and central(the brain, the logistics manager in control of the distribution centre)

levels. This process is known as the control of breathing

The 2 levels of control

1. Local control

Location:Alveoli, alveolar capillaries and bronchioles in localised areas of the lung

Role:To ensure blood and gas go to the appropriate parts of the lung for efficient gas exchange

When: There are localized changes in Co2 and O2

Mechanism: Local adjustments to blood flow (lung perfusion) and oxygen delivery (alveolar ventilation) to

alveoli

2. Central control

Location:The respiratory centres(pairs of nuclei located in the medulla oblongataand the pons) modified

by sensory neurons(peripheral and in the brainscerebrospinal fluid) and higher centres (cerebral cortex)

Role:Adjust the depth and rate of ventilation

When:During both normal breathing and also when there is a larger respiratory demand or conscious control is

needed (e.g. during talking)

Mechanism:Both involuntary (respiratory reflexes involving sensory feedback) and voluntary (higher centres of the

brain) control via the respiratory centres

1. Local control: Getting to the right place at the right time

Local control is automatic control independent of the brains activity

It consists of adjustments to two components:

a) Lung perfusion

b) Alveolar ventilation

Using the supply and demand analogy, it is equivalent to improving the efficiency of the distribution centre by

ensuring more trucks are going to where there is the most product for delivery (in the case of lung perfusion) and

product is being diverted to where it is most needed (alveolar ventilation)

a) Lung perfusion

Local control via lung perfusion ensures that arteriolar blood flow is diverted to where it is needed in the lung

This is achieved through vasoconstriction of arterioles supplying lung areas low in O2

For instance, insufficient O2 in a region of alveoli, characterised by a decreased PO2 (the partial pressure of

oxygen) is recognised by receptors located in the capillaries. As a consequence,vasoconstrictionof arterioles

supplying this area occurs, reducing blood flow and therefore preventing wasted perfusion into poorly

oxygenated alveoli


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Conversely, if alveolar PO2 is high,vasodilationwill occur delivering more deoxygenated blood to these alveoli

aiding optimal gas exchange

b) Alveolar ventilation

Local control via alveolar ventilation ensures optimum conditions for gas exchange

This involves adjusting the size of the bronchioles in response to alveolar PCO2 (the partial pressure of carbon

dioxide), thus, altering the airflow into the alveoli

For instance, a local increase in alveolar PCO2 leads to local bronchodilationdrawing more air into this area

of the lungs and allowing O2 to reach functional alveoli (i.e. those receiving CO2 from the blood) and also

facilitating CO2 removal

In contrast, a decrease in alveolar PCO2 leads to bronchoconstriction, resulting in less air delivery to these

areas
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c) Ventilation/perfusion ratio

Ventilation (V): The amount of O2 reaching alveoli (litres/min).

Normal ventilation: 4 litres of air per minute

Perfusion (Q): The amount of blood flow into the lungs (litres/min)

Normal perfusion: 5 litres of blood per minute

Ventilation/Perfusion ratio: The ratio between the amount of air entering the alveoli and the amount of blood

draining into the lung. Allows an assessment of the efficiency of gas exchange.

The common value for ventilation / perfusion is 4/5 or 0.8

NB: Local control aims at maintaining an optimal V/Q

Pathology and the V/Q ratio


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2. Central control

As opposed to local control, central control directs respiration via the respiratory centres of the brain

These affect the rate and depth of breathing in response to various sensory and higher inputs

It consists of two components.....

a) Involuntary control

b) Voluntary control

Using the analogy of supply and demand, the brain is acting as a logistics manager, receiving information from

various sites along the distribution chain and informing the main distribution centre to respond accordingly. There

are two forms of central control

a) Involuntary control

Involuntary control directs the depth and rate of breathing via outputs from the respiratory centres

These may be modified upon stimulation from sensory receptors in the lungs, respiratory tract and cerebrospinal

fluid to ensure appropriate levels of ventilation

b) Voluntary control

Voluntary control is influenced indirectly by the cerebral cortex and affects the output of the respiratory centres in

the medulla oblongata

Influential factors include emotion, anticipation of exertion and activities requiring alteration to normal breathing

such as playing the trumpet!

Involuntary control: Normal and forced breathing

In order to understand how involuntary control responds to perturbations in the system, we must first

understand how the normal rhythm of breathing occurs. This is down to the respiratory centres in the brain.

Each respiratory rhythmicity centre (in the medulla oblongata) includes a dorsal respiratory group (DRG) and

a ventral respiratory group (VRG), which function in setting the pace of respiration.


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These centres outputs are modified by theapneusticand pneumotaxiccentres of the pons, which regulate

the respiratory rate and depth of respiration under the control of other centres of the brain

Normal breathing cycle (lasting around 5 seconds):

Inhalation occurs in first 2 seconds followed by 3 seconds of exhalation

Inhalation: Within the first stage, the DRG (stimulated by the apneustic centres), enhance the activities of the

inspiratory muscles

Exhalation: In the next 3 seconds, the pneumotaxic centres inhibit the apneustic centres resulting in

unstimulated DRG. These no longer stimulate inhalation anymore, causing passive exhalation

Forced breathing cycle:

During forced breathing, the cooperation of respiratory centres is modified

Inhalation: both the DRG and inspiratory centres of the VRG stimulate the contraction of inspiratory muscles

and inhibition of the expiratory centres of the VRG. This leads to relaxation of expiratory muscles, resulting in

inhalation

Exhalation: The DRG and inspiratory centres of the VRG are inhibited. Meanwhile, expiratory centres of VRG

bring about the contraction of expiratory muscles, causing forced expiration

The respiratory centres and breathing

Involuntary control: Respiratory reflexes

The normal pattern of breathing is modified via sensory reflexes in order to accommodate physiological

changes and maintain homeostasis

In the first stage of this process, different receptors detect changes inside the body and send information to the

central controllers (at the medulla) via sensory afferent nerves The output of the controllers is then modified changing the efferent signal to the effectors (the respiratory

muscles)

Stimulation can be chemical(i.e. changes in PCO2 and pH detected

by chemoreceptors), mechanical(detected by mechanoreceptors) or through changes in

blood pressure(recognised by baroreceptorsin blood vessel walls)


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Below are some examples of the respiratory reflexes....

i) Chemoreceptor reflexes

Chemoreceptors detect changes in the chemical composition of the blood and cerebrospinal fluid. They arecategorised into two groups:

1. Central chemoreceptors:

Location:On the ventrolateral surface of the medulla oblongata

Stimulation:changes in pH and in the cerebrospinal fluid

2. Peripheral chemoreceptors:

Location:a) In the carotid bodies: At the bifurcation of carotid arteries, innervated by the glossopharyngeal (IX)

nerve b) In the aortic bodies: Above and below the aortic arch, innervated by the vagus (X) nerve

Stimulation:Detect a decrease in PO2 (hypoxia) and pH. NB: PCO2 affects pH so peripheral chemoreceptors

will indirectly respond to increased PCO2 (hypercapnea)

Homeostasis: The chemoreceptor reflexes in action

Condition: Hypercapnea (increased arterial PCO2)


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J receptors located in the alveoli and capillaries are stimulated by pulmonary oedemaand products

of inflammationin the interstitium of the lungs

The receptors send information through bronchopulmonary, unmyelinated C-fibres

Once stimulated, C-fibre terminalsrelease sensory neuropeptides, which in turn positively influence rapidly

adapting receptors

This stimulation contributes to particular responses such as rapid shallow breathing,decreased tidal

volume, increased respiratory rate, mucus secretion and cough

v) Head's paradoxical reflex

In the presence of cold block on vagus nerves, the paradoxical reflexoccurs

It contradicts the Hering-Breuer inflation reflex in that inflation is no longer inhibited in the lungs

Therefore, Heads paradoxical reflex leads toirregular deep breaths superimposed on normal breathing

It is recognized to be important in the first breath of babies and also in augmented breathsof adults (sighs)

vi) Muscle spindle reflexes

Muscle spindlesare sensory receptors that are widely located in the intercostal muscleswithin the ribcage

and are involved in a reflex arcnot involving the medulla(sensory neurons synapse directly with motor

neurons)

An increase in respiratory load (i.e. muscle stretching) stimulates the contraction of a large number of

intercostal muscles around the affected muscle spindles

vii) Baroreceptor reflexes

Baroreceptors, located in the carotid sinus and the aortic arch are mainly responsible for the regulation

of blood pressure

They do, however also affect respiratory frequencyand tidal volume. A decreasein intrasinus pressure

brings about a baroreceptor reflex, characterised by increasing respiratory frequency and lowering tidal

volume Similarly increasedpressure results in decreased respiratory rate

Control of ventilationrefers to thephysiologicalmechanisms involved in the control ofphysiologic

ventilation.Gas exchange primarily controls the rate of respiration.

The most important function ofbreathingis gas exchange (ofoxygenandcarbon dioxide). Thus the control of

respiration is centered primarily on how well this is achieved by thelungs.

There are four main centers in thereticular formationand other parts of thebrainstemthat regulate

therespiration rate.

1. Inspiratorycentre - reticular formation, medulla oblongata

2. Expiratorycenter - reticular formation, medulla oblongata

3. Pneumotaxic center- various nuclei of the pons

4. Apneustic center- nucleus of the pons

The first two centers are present on themedulla oblongatawhereas the last two centers on theponsregion of

brain.

Involuntary control of respiration[edit]Ventilatory Pattern[edit]

The pattern of motor stimuli during breathing can be divided into inspiratory and expiratory phases. Inspiration

shows a sudden, ramped increase in motor discharge to the inspiratory muscles (including pharyngeal dilator
http://en.wikipedia.org/wiki/Physiologyhttp://en.wikipedia.org/wiki/Physiologyhttp://en.wikipedia.org/wiki/Physiologyhttp://en.wikipedia.org/wiki/Ventilation_(physiology)http://en.wikipedia.org/wiki/Ventilation_(physiology)http://en.wikipedia.org/wiki/Ventilation_(physiology)http://en.wikipedia.org/wiki/Ventilation_(physiology)http://en.wikipedia.org/wiki/Breathhttp://en.wikipedia.org/wiki/Breathhttp://en.wikipedia.org/wiki/Breathhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Lungshttp://en.wikipedia.org/wiki/Lungshttp://en.wikipedia.org/wiki/Reticular_formationhttp://en.wikipedia.org/wiki/Reticular_formationhttp://en.wikipedia.org/wiki/Reticular_formationhttp://en.wikipedia.org/wiki/Brainstemhttp://en.wikipedia.org/wiki/Brainstemhttp://en.wikipedia.org/wiki/Brainstemhttp://en.wikipedia.org/wiki/Respiration_ratehttp://en.wikipedia.org/wiki/Respiration_ratehttp://en.wikipedia.org/wiki/Respiration_ratehttp://en.wikipedia.org/wiki/Inhalationhttp://en.wikipedia.org/wiki/Inhalationhttp://en.wikipedia.org/wiki/Exhalationhttp://en.wikipedia.org/wiki/Exhalationhttp://en.wikipedia.org/wiki/Pneumotaxic_centerhttp://en.wikipedia.org/wiki/Pneumotaxic_centerhttp://en.wikipedia.org/wiki/Apneustic_centerhttp://en.wikipedia.org/wiki/Apneustic_centerhttp://en.wikipedia.org/wiki/Medulla_oblongatahttp://en.wikipedia.org/wiki/Medulla_oblongatahttp://en.wikipedia.org/wiki/Medulla_oblongatahttp://en.wikipedia.org/wiki/Ponshttp://en.wikipedia.org/wiki/Ponshttp://en.wikipedia.org/wiki/Ponshttp://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=1http://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=1http://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=1http://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=2http://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=2http://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=2http://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=2http://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=1http://en.wikipedia.org/wiki/Ponshttp://en.wikipedia.org/wiki/Medulla_oblongatahttp://en.wikipedia.org/wiki/Apneustic_centerhttp://en.wikipedia.org/wiki/Pneumotaxic_centerhttp://en.wikipedia.org/wiki/Exhalationhttp://en.wikipedia.org/wiki/Inhalationhttp://en.wikipedia.org/wiki/Respiration_ratehttp://en.wikipedia.org/wiki/Brainstemhttp://en.wikipedia.org/wiki/Reticular_formationhttp://en.wikipedia.org/wiki/Lungshttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Breathhttp://en.wikipedia.org/wiki/Ventilation_(physiology)http://en.wikipedia.org/wiki/Ventilation_(physiology)http://en.wikipedia.org/wiki/Physiology


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muscles). Before the end of inspiration, there is a decline in motor discharge. Exhalation is usually silent,

except at highminute ventilationrates.

The mechanism of generation of the ventilatory pattern is not completely understood, but involves the

integration of neural signals by respiratory control centers in themedullaandpons.The nuclei known to be

involved are divided into regions known as the following:

medulla (reticular formation)

ventral respiratory group(nucleus retroambigualis,nucleus ambigus,nucleus parambigualis andthepre-Btzinger complex). The ventral respiratory group controls voluntary forced exhalation andacts to increase the force of inspiration. Regulates rhythm of inhalation and exhalation.

dorsal respiratory group(nucleus tractus solitarii). The dorsal respiratory group controls mostlyinspiratory movements and their timing.

pons

pneumotaxic center.

Coordinates speed of inhalation and exhalation

Sends inhibitory impulses to the inspiratory area

The pneumotaxic center is involved in fine tuning of respiration rate.

apneustic center

Coordinates speed of inhalation and exhalation. Sends stimulatory impulses to the inspiratory areaactivates and prolongs inhalate (long deep

breaths)

overridden by pneumotaxic control from the apneustic area to end inspiration

There is further integration in theanterior horncells of thespinal cord.[citation needed]

Control of ventilatory pattern[edit]

Ventilation is normally controlled by theautonomic nervous system,with only limited voluntary override. An

exception to this isOndine's curse,where autonomic control is lost.

Determinants of ventilatory rate[edit]Ventilatory rate (minute volume) is tightly controlled and determined primarily by blood levels ofcarbon

dioxideas determined bymetabolic rate.Blood levels ofoxygenbecome important inhypoxia.These levels

are sensed bychemoreceptorsin themedulla oblongatafor pH, and thecarotidandaorticbodies for oxygen

and carbon dioxide. Afferent neurons from the carotid bodies and aortic bodies are via theglossopharyngeal

nerve(CN IX) and thevagus nerve(CN X), respectively.

Levels of CO2rise in the blood when the metabolic use of O2is increased beyond the capacity of the lungs to

expel CO2. CO2is stored largely in the blood as bicarbonate (HCO3-) ions, by conversion first to carbonic acid

(H2CO3), by the enzyme carbonic anhydrase, and then by disassociation of this acid to H+

and HCO3-

. Build-upof CO2therefore causes an equivalent build-up of the disassociated hydrogen ion, which, by definition,

decreases the pH of the blood.

During moderateexercise,ventilation increases in proportion tometabolicproduction of carbon dioxide.

During strenuous exercise, ventilation increases more than needed to compensate for carbon dioxide

production. Increased glycolysis facilitates release of protons from ATP and metabolites lowerpHand thus

increase breathing.

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 bymuscle spindlesvia a reflex arc involving the spinal

cord.
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Drugs can greatly influence the control of respiration.Opioidsand anaesthetic drugs tend to depress

ventilation, especially with regards tocarbon dioxideresponse. Stimulants such asamphetaminescan

causehyperventilation.

Pregnancytends to increase ventilation (lowering plasma carbon dioxide tension below normal values). This

is due to increasedprogesteronelevels and results in enhanced gas exchange in theplacenta.

Ventilation is temporarily modified by voluntary acts and complex reflexes such as sneezing, straining,

burping, coughing and vomiting.

Feedback control[edit]

Receptorsplay important roles in the regulation of respiration; central and peripheralchemoreceptors,

andmechanoreceptors.

Central chemoreceptorsof the central nervous system, located on the ventrolateral medullary surface,

are sensitive to thepHof their environment.[1][2]

Peripheral chemoreceptorsact most importantly to detect variation of theoxygenin thearterial blood,in

addition to detecting arterial carbon dioxide and pH.

Mechanoreceptors are located in theairwaysandparenchyma,and are responsible for a variety of

reflex responses. These include:

TheHering-Breuer reflexthat terminates inspiration to prevent over inflation of the lungs, and thereflex responses ofcoughing,airway constriction,andhyperventilation.

The upper airway receptors are responsible for reflex responses such as, sneezing,coughing,closure ofglottis,andhiccups.

Thespinal cordreflex responses include the activation of additional respiratory muscles ascompensation, gasping response, hypoventilation, and an increase in breathing frequency andvolume.

The nasopulmonary and nasothoracicreflexesregulate the mechanism of breathing throughdeepening the inhale. Triggered by the flow of the air, the pressure of the air in thenose,and thequality of the air, impulses from the nasal mucosa are transmitted by the trigeminal nerve to thebreathing centres in thebrainstem,and the generated response is transmitted to thebronchi,theintercostal musclesand thediaphragm.

Voluntary control of respiration[edit]

In addition to involuntary control of respiration by respiratory neuronal networks in the brainstem, respiration

can be affected by higher brain conditions such as emotional state, via input from thelimbic system,

ortemperature,via thehypothalamus,or free will. Voluntary or conscious control of respiration is provided viathecerebral cortex,although chemoreceptor reflex is capable of overriding it.

While breathing can obviously be controlled both consciously and unconsciously, all other basic functions

provided by the brainstem can not be controlled voluntarily. Onlyconscious controlof respiratory neuronal

networks in the reticular formation can effect other basic functions regulated by the brainstem, because of the

inter-meshed character of the reticular formation, e.g. theheart rateinyoga[3]and meditation ("to take a deep

breath").
http://en.wikipedia.org/wiki/Opioidshttp://en.wikipedia.org/wiki/Opioidshttp://en.wikipedia.org/wiki/Opioidshttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Amphetamineshttp://en.wikipedia.org/wiki/Amphetamineshttp://en.wikipedia.org/wiki/Amphetamineshttp://en.wikipedia.org/wiki/Hyperventilationhttp://en.wikipedia.org/wiki/Hyperventilationhttp://en.wikipedia.org/wiki/Hyperventilationhttp://en.wikipedia.org/wiki/Pregnancyhttp://en.wikipedia.org/wiki/Pregnancyhttp://en.wikipedia.org/wiki/Progesteronehttp://en.wikipedia.org/wiki/Progesteronehttp://en.wikipedia.org/wiki/Progesteronehttp://en.wikipedia.org/wiki/Placentahttp://en.wikipedia.org/wiki/Placentahttp://en.wikipedia.org/wiki/Placentahttp://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=5http://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=5http://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=5http://en.wikipedia.org/wiki/Sensory_receptorhttp://en.wikipedia.org/wiki/Sensory_receptorhttp://en.wikipedia.org/wiki/Chemoreceptorhttp://en.wikipedia.org/wiki/Chemoreceptorhttp://en.wikipedia.org/wiki/Chemoreceptorhttp://en.wikipedia.org/wiki/Mechanoreceptorhttp://en.wikipedia.org/wiki/Mechanoreceptorhttp://en.wikipedia.org/wiki/Mechanoreceptorhttp://en.wikipedia.org/wiki/Central_chemoreceptorshttp://en.wikipedia.org/wiki/Central_chemoreceptorshttp://en.wikipedia.org/wiki/PHhttp://en.wikipedia.org/wiki/PHhttp://en.wikipedia.org/wiki/PHhttp://en.wikipedia.org/wiki/Control_of_respiration#cite_note-Coates-1http://en.wikipedia.org/wiki/Control_of_respiration#cite_note-Coates-1http://en.wikipedia.org/wiki/Control_of_respiration#cite_note-Coates-1http://en.wikipedia.org/wiki/Peripheral_chemoreceptorshttp://en.wikipedia.org/wiki/Peripheral_chemoreceptorshttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Arterial_bloodhttp://en.wikipedia.org/wiki/Arterial_bloodhttp://en.wikipedia.org/wiki/Arterial_bloodhttp://en.wikipedia.org/wiki/Mechanoreceptorshttp://en.wikipedia.org/wiki/Mechanoreceptorshttp://en.wikipedia.org/wiki/Airwayhttp://en.wikipedia.org/wiki/Airwayhttp://en.wikipedia.org/wiki/Airwayhttp://en.wikipedia.org/wiki/Parenchymahttp://en.wikipedia.org/wiki/Parenchymahttp://en.wikipedia.org/wiki/Parenchymahttp://en.wikipedia.org/wiki/Hering-Breuer_reflexhttp://en.wikipedia.org/wiki/Hering-Breuer_reflexhttp://en.wikipedia.org/wiki/Hering-Breuer_reflexhttp://en.wikipedia.org/wiki/Coughinghttp://en.wikipedia.org/wiki/Coughinghttp://en.wikipedia.org/wiki/Coughinghttp://en.wikipedia.org/wiki/Airway_constrictionhttp://en.wikipedia.org/wiki/Airway_constrictionhttp://en.wikipedia.org/wiki/Airway_constrictionhttp://en.wikipedia.org/wiki/Hyperventilationhttp://en.wikipedia.org/wiki/Hyperventilationhttp://en.wikipedia.org/wiki/Hyperventilationhttp://en.wikipedia.org/wiki/Sneezinghttp://en.wikipedia.org/wiki/Sneezinghttp://en.wikipedia.org/wiki/Sneezinghttp://en.wikipedia.org/wiki/Glottishttp://en.wikipedia.org/wiki/Glottishttp://en.wikipedia.org/wiki/Glottishttp://en.wikipedia.org/wiki/Hiccupshttp://en.wikipedia.org/wiki/Hiccupshttp://en.wikipedia.org/wiki/Hiccupshttp://en.wikipedia.org/wiki/Spinal_cordhttp://en.wikipedia.org/wiki/Spinal_cordhttp://en.wikipedia.org/wiki/Spinal_cordhttp://en.wikipedia.org/wiki/Reflexhttp://en.wikipedia.org/wiki/Reflexhttp://en.wikipedia.org/wiki/Reflexhttp://en.wikipedia.org/wiki/Nosehttp://en.wikipedia.org/wiki/Nosehttp://en.wikipedia.org/wiki/Nosehttp://en.wikipedia.org/wiki/Brainstemhttp://en.wikipedia.org/wiki/Brainstemhttp://en.wikipedia.org/wiki/Brainstemhttp://en.wikipedia.org/wiki/Bronchushttp://en.wikipedia.org/wiki/Bronchushttp://en.wikipedia.org/wiki/Bronchushttp://en.wikipedia.org/wiki/Intercostal_muscleshttp://en.wikipedia.org/wiki/Intercostal_muscleshttp://en.wikipedia.org/wiki/Intercostal_muscleshttp://en.wikipedia.org/wiki/Thoracic_diaphragmhttp://en.wikipedia.org/wiki/Thoracic_diaphragmhttp://en.wikipedia.org/wiki/Thoracic_diaphragmhttp://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=6http://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=6http://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=6http://en.wikipedia.org/wiki/Limbic_systemhttp://en.wikipedia.org/wiki/Limbic_systemhttp://en.wikipedia.org/wiki/Limbic_systemhttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Hypothalamushttp://en.wikipedia.org/wiki/Hypothalamushttp://en.wikipedia.org/wiki/Hypothalamushttp://en.wikipedia.org/wiki/Cerebral_cortexhttp://en.wikipedia.org/wiki/Cerebral_cortexhttp://en.wikipedia.org/wiki/Cerebral_cortexhttp://en.wikipedia.org/wiki/Breathing#Conscious_controlhttp://en.wikipedia.org/wiki/Breathing#Conscious_controlhttp://en.wikipedia.org/wiki/Breathing#Conscious_controlhttp://en.wikipedia.org/wiki/Heart_ratehttp://en.wikipedia.org/wiki/Heart_ratehttp://en.wikipedia.org/wiki/Heart_ratehttp://en.wikipedia.org/wiki/Yoga#Ascetic_practiceshttp://en.wikipedia.org/wiki/Yoga#Ascetic_practiceshttp://en.wikipedia.org/wiki/Yoga#Ascetic_practiceshttp://en.wikipedia.org/wiki/Yoga#Ascetic_practiceshttp://en.wikipedia.org/wiki/Yoga#Ascetic_practiceshttp://en.wikipedia.org/wiki/Yoga#Ascetic_practiceshttp://en.wikipedia.org/wiki/Heart_ratehttp://en.wikipedia.org/wiki/Breathing#Conscious_controlhttp://en.wikipedia.org/wiki/Cerebral_cortexhttp://en.wikipedia.org/wiki/Hypothalamushttp://en.wikipedia.org/wiki/Temperaturehttp://en.wikipedia.org/wiki/Limbic_systemhttp://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=6http://en.wikipedia.org/wiki/Thoracic_diaphragmhttp://en.wikipedia.org/wiki/Intercostal_muscleshttp://en.wikipedia.org/wiki/Bronchushttp://en.wikipedia.org/wiki/Brainstemhttp://en.wikipedia.org/wiki/Nosehttp://en.wikipedia.org/wiki/Reflexhttp://en.wikipedia.org/wiki/Spinal_cordhttp://en.wikipedia.org/wiki/Hiccupshttp://en.wikipedia.org/wiki/Glottishttp://en.wikipedia.org/wiki/Sneezinghttp://en.wikipedia.org/wiki/Hyperventilationhttp://en.wikipedia.org/wiki/Airway_constrictionhttp://en.wikipedia.org/wiki/Coughinghttp://en.wikipedia.org/wiki/Hering-Breuer_reflexhttp://en.wikipedia.org/wiki/Parenchymahttp://en.wikipedia.org/wiki/Airwayhttp://en.wikipedia.org/wiki/Mechanoreceptorshttp://en.wikipedia.org/wiki/Arterial_bloodhttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Peripheral_chemoreceptorshttp://en.wikipedia.org/wiki/Control_of_respiration#cite_note-Coates-1http://en.wikipedia.org/wiki/Control_of_respiration#cite_note-Coates-1http://en.wikipedia.org/wiki/PHhttp://en.wikipedia.org/wiki/Central_chemoreceptorshttp://en.wikipedia.org/wiki/Mechanoreceptorhttp://en.wikipedia.org/wiki/Chemoreceptorhttp://en.wikipedia.org/wiki/Sensory_receptorhttp://en.wikipedia.org/w/index.php?title=Control_of_respiration&action=edit&section=5http://en.wikipedia.org/wiki/Placentahttp://en.wikipedia.org/wiki/Progesteronehttp://en.wikipedia.org/wiki/Pregnancyhttp://en.wikipedia.org/wiki/Hyperventilationhttp://en.wikipedia.org/wiki/Amphetamineshttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Opioids

the control of breathing.docx

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