Juxtacapillary receptors

Juxtacapillary receptors, J-receptors, or pulmonary C-fiber receptors are sensory nerve endings located within the alveolar walls in juxtaposition to the pulmonary capillaries of the lung, and are innervated by fibers of the vagus nerve.^[1] Although their functional role is unclear, J-receptors respond to events such as pulmonary edema, pulmonary emboli, pneumonia, congestive heart failure and barotrauma, which cause a decrease in oxygenation and thus lead to an increase in respiration.^[2] They may be also stimulated by hyperinflation of the lung as well as intravenous or intracardiac administration of chemicals such as capsaicin.^[3] The stimulation of the J-receptors causes a reflex increase in breathing rate, and is also thought to be involved in the sensation of dyspnea, the subjective sensation of difficulty breathing.^[4]^[5] The reflex response that is produced is apnea followed by rapid breathing, bradycardia, and hypotension (pulmonary chemoreflex). The physiologic role of this reflex is uncertain, but it probably occurs in pathologic states such as pulmonary congestion or embolization.^[3] These receptors were discovered by Autar Paintal.^[6]

Because these receptors have been found in the walls of bronchi, the larynx, and the nose, they appear to be part of a widespread population of nociceptors found in most tissue. For this reason, they are now usually referred to as pulmonary C-fiber receptors.^[7]

References

^ Sircar, Sabyasachi (2008). Principles of Medical Physiology. pp. 350–51. ISBN 978-1-58890-572-7.
^ Guyton (2011). "Regulation of Respiration". Textbook of Medical Physiology. Saunders Elsevier. ISBN 978-1-4160-4574-8.
^ ^a ^b Ganong (2016). "Regulation of Respiration". Review of Medical Physiology, 25th ed. McGraw-Hill Education. p. 662. ISBN 978-0-07-184897-8.
^ A.A. Majid, A.N.Kingsworth, Fundamentals of Surgical Practice. Cambridge, MA: Cambridge University Press, 2006. ISBN 0-521-67706-8.
^ J.C. Bennett, F.Plum ed. Cecil Textbook of Medicine, 20th ed., W.B. Saunders, Philadelphia PA, 1996. ISBN 0-7216-3574-1
^ "A.S. Paintal — a celebrated physiologist". The Hindu. Chennai, India. 19 January 2006. Archived from the original on 12 July 2006.
^ Widdicombe, John (2006). "Reflexes from the lungs and airways: Historical perspective". Journal of Applied Physiology. 101 (2): 628–634. doi:10.1152/japplphysiol.00155.2006. PMID 16601307.

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[1] Sircar, Sabyasachi (2008). Principles of Medical Physiology. pp. 350–51. ISBN 978-1-58890-572-7.

[2] Guyton (2011). "Regulation of Respiration". Textbook of Medical Physiology. Saunders Elsevier. ISBN 978-1-4160-4574-8.

[Ganong-3] Ganong (2016). "Regulation of Respiration". Review of Medical Physiology, 25th ed. McGraw-Hill Education. p. 662. ISBN 978-0-07-184897-8.

[4] A.A. Majid, A.N.Kingsworth, Fundamentals of Surgical Practice. Cambridge, MA: Cambridge University Press, 2006. ISBN 0-521-67706-8.

[5] J.C. Bennett, F.Plum ed. Cecil Textbook of Medicine, 20th ed., W.B. Saunders, Philadelphia PA, 1996. ISBN 0-7216-3574-1

[6] "A.S. Paintal — a celebrated physiologist". The Hindu. Chennai, India. 19 January 2006. Archived from the original on 12 July 2006.

[7] Widdicombe, John (2006). "Reflexes from the lungs and airways: Historical perspective". Journal of Applied Physiology. 101 (2): 628–634. doi:10.1152/japplphysiol.00155.2006. PMID 16601307.

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v t e Respiratory physiology
Respiration	breath inhalation exhalation obligate nasal breathing respiratory rate respirometer pulmonary surfactant compliance elastic recoil hysteresivity airway resistance bronchial hyperresponsiveness constriction dilatation mechanical ventilation
Control	pons pneumotaxic center apneustic center medulla dorsal respiratory group ventral respiratory group chemoreceptors central peripheral pulmonary stretch receptors Hering–Breuer reflex
Lung volumes	VC FRC Vt dead space CC PEF calculations respiratory minute volume FEV1/FVC ratio Lung function tests spirometry body plethysmography peak flow meter nitrogen washout
Circulation	pulmonary circulation hypoxic pulmonary vasoconstriction pulmonary shunt
Interactions	ventilation (V) Perfusion (Q) Ventilation/perfusion ratio V/Q scan zones of the lung gas exchange pulmonary gas pressures alveolar gas equation alveolar–arterial gradient hemoglobin oxygen–hemoglobin dissociation curve (Oxygen saturation 2,3-BPG Bohr effect Haldane effect) carbonic anhydrase (chloride shift) oxyhemoglobin respiratory quotient arterial blood gas diffusion capacity (DLCO)
Insufficiency	high altitude death zone oxygen toxicity hypoxia