Central chemoreceptors

Central chemoreceptors of the central nervous system, located on the ventrolateral medullary surface, are sensitive to the pH of their environment.

These act to detect the changes in pH of nearby cerebral spinal fluid (CSF) that are indicative of altered oxygen or carbon dioxide concentrations available to brain tissues. An increase in carbon dioxide tension of the arteries, often resulting from increased CO₂ intake (hypercapnia), indirectly causes the blood to become more acidic; the cerebral spinal fluid pH is closely comparable to the plasmas, as carbon dioxide easily diffuses across the blood/brain barrier.

However, a change in plasma pH alone will not stimulate central chemoreceptors as H+ are not be able to diffuse across the blood-brain barrier into the CSF. Only CO₂ levels affect this as it can diffuse across, reacting with H₂O to form carbonic acid and thus decrease pH. Central chemoreception remains, in this way, distinct from peripheral chemoreceptors.

The central chemoreception system has also been shown experimentally to respond to hypercapnic hypoxia (elevated CO₂, decreased O₂) and aqueous sodium cyanide injection into the whole animal and in vitro slice preparation. These methods can be used to mimic some forms of hypoxic hypoxia and they are currently being studied including the detection of variation in arterial CO₂ tension acting as a quick-response-system for short term (or emergency) regulation.

This system utilizes a negative feedback system, therefore if the pH of the cerebral spinal fluid does not compare to an ideal “set” level, then the receptor will send an error signal to the effectors and appropriate action may be executed.

See also

• Chemoreceptors
• Peripheral chemoreceptors

External links

• Physiology at MCG 4/4ch6/s4ch6_21
• Overview at cvphysiology.com