Chemoreceptors in the Medulla

The chemoreceptors most sensitive to changes in the arterial PCO2 are located in the ventral area of the medulla oblongata, near the exit of the ninth and tenth cranial nerves. These chemoreceptor neurons are anatomically separate from, but synaptically communicate with, the neurons of the respiratory control center in the medulla.

An increase in arterial PCO2 causes a rise in the H+ concentration of the blood as a result of increased carbonic acid concentrations. The H+ in the blood, however, cannot cross the blood-brain barrier, and thus cannot influence the medullary chemoreceptors. Carbon dioxide in the arterial blood can cross the blood-brain barrier and, through the formation of carbonic acid, can lower the pH of cerebrospinal fluid (fig. 16.30). This

Hypoventilation

E JE

Normal ventilation (Pco2= 40 ± 2)

Hyperventilation

Chemoreceptor neurons

CO2J

HCO3

-Medulla oblongata

Blood Csf Barrier

— Blood-CSF barrier

— Capillary blood

-Cerebrospinal fluid (CSF)

— Blood-CSF barrier

— Capillary blood

Total minute volume (L/min)

■ Figure 16.28 The relationship between total minute volume and arterial PCO2. Notice that these are inversely related: when the total minute volume increases by a factor of 2, the arterial Pco2 decreases by half. The total minute volume measures breathing, and is equal to the amount of air in each breath (the tidal volume) multiplied by the number of breaths per minute. The PCO2 measures the CO2 concentration of arterial blood plasma.

Pco2 And Total Minute Volume

■ Figure 16.29 Chemoreceptor control of breathing. This figure depicts the negative feedback control of ventilation through changes in blood PCO2 and pH. The blood-brain barrier, represented by the orange box, allows CO2 to pass into the cerebrospinal fluid but prevents the passage of H+.

■ Figure 16.30 How blood CO2 affects chemoreceptors in the medulla oblongata. An increase in blood CO2 stimulates breathing indirectly by lowering the pH of blood and cerebrospinal fluid (CSF). This figure illustrates how a rise in blood CO2 increases the H+ concentration (lowers the pH) of CSF and thereby stimulates chemoreceptor neurons in the medulla oblongata.

fall in cerebrospinal fluid pH directly stimulates the chemoreceptors in the medulla when there is a rise in arterial Pco2-

The chemoreceptors in the medulla are ultimately responsible for 70% to 80% of the increased ventilation that occurs in response to a sustained rise in arterial Pœ2. This response, however, takes several minutes. The immediate increase in ventilation that occurs when PCO2 rises is produced by stimulation of the peripheral chemoreceptors.

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Responses

  • elisa negassi
    Can carbonic acid pass the blood brain barrier?
    7 years ago
  • leena
    How pco2 penetrate blood brain barrier?
    7 years ago
  • annett schneider
    How blood brain barrirer influences ventilation?
    7 years ago
  • heike
    How is the medulla indirectly affected by co2 levels in blood?
    7 years ago
  • Ute
    How is CO2 detected by the medulla oblongata?
    7 years ago
  • bernd friedmann
    What stimulates the chemoreceptors in the medulla?
    7 years ago
  • Fatima
    What chemoreceptor measures pH and CO2?
    7 years ago
  • George
    What chemoreceptors respond to changes in cerebralspinal fluid?
    7 years ago
  • jonas ebersbacher
    How is blood P co2 detected in the human body?
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  • fatima
    How is blood pco2 detected in the human body?
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  • anna-liisa
    How blood CO2 affects chemoreceptors in the medulla oblongata?
    7 years ago
  • BRENDAN KELLY
    Where are the chemoreceptors located that stimulate breathing?
    6 years ago
  • asfaha
    Which chemoreceptor is most sensitive medulla or carotid body?
    6 years ago
  • selamawit
    How can CO2 change pH and how stimulates chemoreceptors?
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  • pinja
    What are the chemoreceptors in the medulla oblongata called?
    6 years ago
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    How to stimulate the madula oblingata?
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    What stimulates an increase of chemoreceptor center in the medulla?
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    What are chemoreceptors called that are located in the medulla oblongata?
    5 years ago
  • bisrat
    What is the function of the chemoreceptor of the kidney?
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    What is function of chemoreceptors in medulla oblongata?
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  • lilly
    Which chemoreceptors measures ph and CO2 only?
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  • Adam Quezada
    What are chemoreceptors in the medulla sensitive to?
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  • Kifle
    What is monitored by chemoreceptors in medulla?
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    Are chemoreceptors in medulla obulongata?
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  • william
    Which chemo receptor measures ph and co2?
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  • Jens
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  • kenneth
    What stimulates medulla receptors?
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    What is medullary chemoreceptors?
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    What are chemoreceptors input of the respiratory centers of the medulla oblongata?
    3 years ago
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    What directly stimulate the chemoreceptors in the medulla olongata?
    3 years ago
  • pamphila
    What stimulates the chemoreceptors to function?
    3 years ago
  • romolo
    WHEN THE MEDULLA FALLS WHAT IS THATCALLED?
    3 years ago
  • calan
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    3 years ago
  • megan shaw
    How the body senses and fixes increased co2?
    2 years ago
  • Daniel
    What is located in the medulla and are most sensitive to changes in the blood pH and carbon dioxide?
    2 years ago
  • robert drescher
    What are chemoreceptors in the medulla oblongata not sensitive to?
    2 years ago
  • kassie
    Which receptors will detect the increases in Pco2 In the blood respiratory system?
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  • fastred
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  • kirk
    How does pH stimulates respiratory center?
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  • Leea
    How the medulla detect o2 and co2 levels?
    1 year ago
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    What are chemoreceptors in the brain?
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    What is the relationship between testosterone and the medulla oblongata?
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    What do chemo receptors in the medulla respond to?
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  • donnamira diggle
    Does oxygen influence chemoreceptors in the medulla oblongata?
    11 months ago
  • Sirkka
    What does the medulla oblongata do when o2 co2 h increase?
    11 months ago
  • angelica
    Why do chemoreceptors in medulla oblongata have such a big response?
    10 months ago
  • Elsa Takko
    Where are the chemoreceptors that monitor blood levels of O2, CO2 & H located?
    10 months ago
  • AIDAN
    What do the chemoreceptors in the medulla respond to?
    9 months ago
  • rayan
    How does medulla respond to high co2?
    9 months ago
  • dylan
    How does the medulla oblongata respond to carbonic acid?
    9 months ago
  • pansy
    Which chemoreceptors measure ph and co2?
    8 months ago
  • mary visser
    What is a disease that affects chemoreceptors?
    7 months ago
  • MARTHA
    What the receptors in the thermoregulatolary sensor of the brain directly monitor changes of what?
    6 months ago
  • carrie
    How does the medulla oblongata detect that the body is exercising?
    5 months ago
  • LUKAS
    What occurs when the chemoreceptors in the medulla oblongata detect a low blood pH?
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  • Iole Mazzi
    What changes in the body will stimulate the respiratory center in the medulla oblongata to respond?
    4 months ago
  • NIKLAS
    How co2 in blood medulla oblongfatta?
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  • Temesgen
    Which of the following is not monitored by chemoreceptor?
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    4 months ago
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    How do medulla chemoreceptors work?
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  • Aurelia
    How is the centre in thge medulla oblogata stimulated by changes in the blood pH?
    3 months ago
  • holfast
    Why pCo2 is better stimulus for brain medullary chemosensor?
    3 months ago
  • Heikki
    How does the brain react to blood ph changes?
    3 months ago
  • futsum idris
    How the respiratory centre in the medulla stimulated by changes in the bloods co2?
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  • Estella
    How does the medulla oblongata sense carbon dioxide levels?
    3 months ago
  • Cottar
    Can co2 cross the blood brain barrier?
    3 months ago
  • christine
    How do chemoreceptors control the ponjs?
    3 months ago
  • Mathias
    How chemo receptor changes blood ph?
    2 months ago
  • Macy
    How chemoreceptor control PH?
    2 months ago
  • Cheryl
    What monitors the ph of the blood brain barrier?
    2 months ago
  • mezan
    What does the chemorecetors det6ect in the meddulla?
    27 days ago
  • Ettore Trentini
    How are changes in pCO2 related to changes in hydrogen ions detected by this sensor?
    11 hours ago
  • lalia
    What happend if the carbon dioxide rises in the medualla?
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