Bainbridge reflex

The Bainbridge reflex (or Bainbridge effect or atrial reflex) is a cardiovascular reflex causing an increase in heart rate in response to increased stretching of the wall of the right atrium and/or the inferior vena cava as a result of increased venous filling (i.e., increased preload). It is detected by stretch receptors in the wall of the right atrium, the afferent limb is via the vagus nerve, it is regulated by a center in the medulla oblongata of the brain,[1] and the efferent limb involves reduced vagal activity and increased sympathetic nervous system outflow.[2]

Mechanistically, the increased heart rate evoked by the Bainbridge reflex acts to match heart rate (and hence cardiac output) to effective circulating blood volume on a beat-to-beat basis. This, in combination with other cardiovascular reflexes, helps maintain homeostatic equilibrium of the circulation.[3] The Bainbridge reflex may also contribute to respiratory sinus arrhythmia as intrathoracic pressure decreases during inspiration causing increased venous return.[3][4]

The reflex is named after Francis Arthur Bainbridge, an English physiologist. The Bainbridge reflex was one of the first neural cardiovascular reflexes to be described and initiated a period of intense research into neural regulation of the heart.[5]

  1. ^ Boron WF, Boulpaep EL, eds. (2017). Medical Physiology (3rd ed.). Philadelphia, PA: Elsevier. pp. 547–548. ISBN 978-1-4557-4377-3.
  2. ^ Crystal GJ, Salem MR (March 2012). "The Bainbridge and the "reverse" Bainbridge reflexes: history, physiology, and clinical relevance". Anesthesia and Analgesia. 114 (3): 520–532. doi:10.1213/ANE.0b013e3182312e21. PMID 21965361.
  3. ^ a b Pakkam ML, Moore MJ (2024). "Physiology, Bainbridge Reflex". StatPearls. Treasure Island (FL): StatPearls Publishing. PMID 31082061. Retrieved 2024-12-12.
  4. ^ Mortola JP, Marghescu D, Siegrist-Johnstone R (April 2015). "Respiratory sinus arrhythmia in young men and women at different chest wall configurations". Clinical Science. 128 (8): 507–516. doi:10.1042/CS20140543. PMID 25387977.
  5. ^ Hakumäki MO (June 1987). "Seventy years of the Bainbridge reflex". Acta Physiologica Scandinavica. 130 (2): 177–185. doi:10.1111/j.1748-1716.1987.tb08126.x. PMID 3300168.
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