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 a change in pH of the cerebral spinal fluid that are indicative of a change in oxygen or carbon dioxide concentration available to brain tissues. An increase in carbon dioxide tension of the arteries, often resulting from increased CO₂ intake (hypoxia) indirectly cause the blood to become more acidic; the cerebral spinal fluid pH is closely comparable to the plasma pH, as carbon dioxide easily diffuses across the blood/brain barrier.

However, it is important to note that a change in plasma pH will not stimulate central chemoreceptors as H+ will not be able to diffuse into the CSF. Only CO₂ levels affect this as it can diffuse across into the CSF, forming H+ and decreasing pH. Central chemoreception remains, in this way, distinct from peripheral chemoreceptors.

This 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 [Solomon IC, Edelman NH, Neubauer, JA. Pre-Bötzinger complex functions as a central hypoxia chemosensor for respiration "in vivo". J Neurophysiol. 83(5):2854-68, 2000.] 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.

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External links

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* [http://www.cvphysiology.com/Blood%20Pressure/BP014.htm Overview at cvphysiology.com]