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?
    8 years ago
  • leena
    How pco2 penetrate blood brain barrier?
    8 years ago
  • annett schneider
    How blood brain barrirer influences ventilation?
    8 years ago
  • heike
    How is the medulla indirectly affected by co2 levels in blood?
    8 years ago
  • Ute
    How is CO2 detected by the medulla oblongata?
    8 years ago
  • bernd friedmann
    What stimulates the chemoreceptors in the medulla?
    8 years ago
  • Fatima
    What chemoreceptor measures pH and CO2?
    8 years ago
  • jonas ebersbacher
    How is blood P co2 detected in the human body?
    8 years ago
  • fatima
    How is blood pco2 detected in the human body?
    8 years ago
  • anna-liisa
    How blood CO2 affects chemoreceptors in the medulla oblongata?
    8 years ago
  • BRENDAN KELLY
    Where are the chemoreceptors located that stimulate breathing?
    7 years ago
  • asfaha
    Which chemoreceptor is most sensitive medulla or carotid body?
    7 years ago
  • selamawit
    How can CO2 change pH and how stimulates chemoreceptors?
    7 years ago
  • pinja
    What are the chemoreceptors in the medulla oblongata called?
    7 years ago
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    7 years ago
  • evie
    What stimulates an increase of chemoreceptor center in the medulla?
    7 years ago
  • harrison duncan
    What are chemoreceptors called that are located in the medulla oblongata?
    6 years ago
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    6 years ago
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    6 years ago
  • lilly
    Which chemoreceptors measures ph and CO2 only?
    6 years ago
  • Adam Quezada
    What are chemoreceptors in the medulla sensitive to?
    5 years ago
  • Kifle
    What is monitored by chemoreceptors in medulla?
    5 years ago
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    5 years ago
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    5 years ago
  • Jens
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    5 years ago
  • kenneth
    What stimulates medulla receptors?
    5 years ago
  • olivier
    What is medullary chemoreceptors?
    4 years ago
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    4 years ago
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    4 years ago
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    What stimulates the chemoreceptors to function?
    4 years ago
  • romolo
    WHEN THE MEDULLA FALLS WHAT IS THATCALLED?
    4 years ago
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    4 years ago
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    How the body senses and fixes increased co2?
    3 years ago
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    What is located in the medulla and are most sensitive to changes in the blood pH and carbon dioxide?
    3 years ago
  • robert drescher
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    3 years ago
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    3 years ago
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    3 years ago
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    2 years ago
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    2 years ago
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    2 years ago
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    2 years ago
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    2 years ago
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    Does oxygen influence chemoreceptors in the medulla oblongata?
    2 years ago
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    What does the medulla oblongata do when o2 co2 h increase?
    2 years ago
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    2 years ago
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    Where are the chemoreceptors that monitor blood levels of O2, CO2 & H located?
    2 years ago
  • AIDAN
    What do the chemoreceptors in the medulla respond to?
    2 years ago
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    How does medulla respond to high co2?
    2 years ago
  • dylan
    How does the medulla oblongata respond to carbonic acid?
    2 years ago
  • pansy
    Which chemoreceptors measure ph and co2?
    2 years ago
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    What is a disease that affects chemoreceptors?
    1 year ago
  • MARTHA
    What the receptors in the thermoregulatolary sensor of the brain directly monitor changes of what?
    1 year ago
  • carrie
    How does the medulla oblongata detect that the body is exercising?
    1 year ago
  • LUKAS
    What occurs when the chemoreceptors in the medulla oblongata detect a low blood pH?
    1 year ago
  • Iole Mazzi
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    1 year ago
  • NIKLAS
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    1 year ago
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    1 year ago
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    1 year ago
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    1 year ago
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    1 year ago
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    1 year ago
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    1 year ago
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    1 year ago
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    1 year ago
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    1 year ago
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    1 year ago
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    1 year ago
  • Macy
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    1 year ago
  • Cheryl
    What monitors the ph of the blood brain barrier?
    1 year ago
  • mezan
    What does the chemorecetors det6ect in the meddulla?
    11 months ago
  • Ettore Trentini
    How are changes in pCO2 related to changes in hydrogen ions detected by this sensor?
    10 months ago
  • lalia
    What happend if the carbon dioxide rises in the medualla?
    10 months ago
  • Ensio
    Why does the medulla oblongata enlarge?
    10 months ago
  • henry
    What hormone is relased to reduce co2 in blood via the inspiratory area of the medulla?
    9 months ago
  • GIORGIO
    What stimulus do chemoreceptors monitor?
    8 months ago
  • susanne
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    7 months ago
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    7 months ago
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    7 months ago
  • Courtney
    How the medulla oblongata detects exercise?
    6 months ago
  • Paladin
    How can CO2 in the blood stimulate chemoreceptors in the brain that respond to pH changes?
    6 months ago
  • lloyd
    What are the chemo receptors that monitor blood levels of o2,co2&h?
    5 months ago
  • Peter Fleischer
    What is located in the medulla and are most sensitive to change in the bloodph and carbon dioxide?
    4 months ago
  • candida
    What is sensed by the medulla co2?
    4 months ago
  • aziz
    How would the medulla correct increased carbon dioxide?
    4 months ago
  • Mark
    What gas in the csf do central chemoreceptors in the medulla respond to?
    4 months ago
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    What is the concentration of carbon dioxide monitored by medulla?
    2 months ago
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    How brain responds to high co2 in blood?
    2 months ago
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    2 months ago
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    What are the specific chemoreceptors that respond to changes on blood gas concentration?
    2 months ago
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    How does the medulla oblongata return blood co2?
    1 month ago
  • kelli
    What does the medulla do when the blood ph decreases?
    1 month ago
  • orlagh
    What nerve is stimulated by increased co2?
    1 month ago
  • Kibra
    Why is co2 monitored not oxygen by the medulla oblongata?
    1 month ago
  • barry
    What happens when chemoreceptors detect high levels of h?
    30 days ago
  • gringamor
    Why is the medulla oblongata of cetaceans less sensitive to CO2 levels?
    20 days ago
  • Lara
    How is h lowered in the cerebrospinal fluid?
    9 days ago

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