A chemoreceptor, also known as chemosensor, is a sensory receptor that transduces a chemical signal into an action potential. In more general terms, a chemosensor detects certain chemical stimuli in the environment.


There are two main classes of the chemosensor: direct and distance.

Sensory Organs

When inputs from the environment are significant to the survival of the organism, the input must be detected. As all life processes are ultimately based on chemistry it is natural that detection and passing on of the external input will involve chemical events. The chemistry of the environment is, of course, relevant to survival, and detection of chemical input from the outside may well articulate directly with cell chemicals.

Chemoreception is important for the detection of food, habitat, conspecifics including mates, and predators. For example, the emissions of a predator's food source, such as odors or pheromones, may be in the air or on a surface where the food source has been. Cells in the head, usually the air passages or mouth, have chemical receptors on their surface that change when in contact with the emissions. It passes in either chemical or electrochemical form to the central processor, the brain or spinal cord. The resulting output from the CNS (central nervous system) makes body actions that will engage the food and enhance survival.

In Physiology

Control of Breathing

Particular chemoreceptors, called ASICs, detect the levels of carbon dioxide in the blood. To do this, they monitor the concentration of hydrogen ions in the blood, which decrease the pH of the blood. This can be a direct consequence of an increase in carbon dioxide concentration, because aqueous carbon dioxide in the presence of carbonic anhydrase reacts to form a proton and a bicarbonate ion.

The response is that the respiratory centre (in the medulla), sends nervous impulses to the external intercostal muscles and the diaphragm, via the intercostal nerve and the phrenic nerve, respectively, to increase breathing rate and the volume of the lungs during inhalation.

Chemoreceptors that regulate the depth and rhythm of breathing are broken down into two categories.

Heart rate

The response to stimulation of chemoreceptors on the heart rate is complicated. Stimulation of peripheral chemoreceptors directly activates the medullary vagal center and slows the heart rate. However, a number of other factors are usually at play in this situation which obscure this response. These factors include activation of stretch receptors due to increased ventilation and the release of circulating catecholamines. Hence, although the stimulation of peripheral chemoreceptors causes bradycardia, this may not be the net result.[5]

See also


  1. Shi, P.; Zhang, J. (2009). "Extraordinary Diversity of Chemosensory Receptor Gene Repertoires Among Vertebrates". Chemosensory Systems in Mammals, Fishes, and Insects. Results and Problems in Cell Differentiation. 47. pp. 57–75. doi:10.1007/400_2008_4. ISBN 978-3-540-69918-7.
  2. 1 2 Chapman RF (1998) "Chemoreception" in The Insects: structure and function 4th edition. Cambridge University Press, Cambridge. 639.
  4. Satir, Peter; Christensen, Søren T. (2008). "Structure and function of mammalian cilia". Histochemistry and Cell Biology. 129 (6): 687–93. doi:10.1007/s00418-008-0416-9. PMC 2386530Freely accessible. PMID 18365235.
  5. Levy, MN; AJ Pappano (2007). Cardiovascular Physiology 9ed. Philadelphia USA: Elsevier. pp. 89–91.

External links

Wikisource has the text of a 1920 Encyclopedia Americana article about Chemoreceptor.
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