Editing Reflex (section)

{{Short description|Automatic, involuntary response to a stimulus}}
{{cs1 config|name-list-style=vanc}}
{{Other uses|Reflex (disambiguation)}}
{{Redirect|Reflectory|the album|Reflectory (album){{!}}''Reflectory'' (album)}}
{{human centric|date=September 2022}}

In [[biology]], a '''reflex''', or '''reflex action''', is an involuntary, unplanned sequence or action<ref>{{cite web |author=parveen |date=November 11, 2020 |title=Reflex action {{!}} Definition, Types and Mechanism and Important solved questions |url=https://www.crackyourtarget.com/reflex-action.html |access-date=3 April 2021 |publisher=Crack Your Target}}</ref> and nearly instantaneous response to a [[Stimulus (physiology)|stimulus]].<ref>Purves (2004). ''Neuroscience: Third Edition''. Massachusetts, Sinauer Associates, Inc. {{ISBN|0-87893-725-0}}</ref><ref name="M-W">{{cite web |title=Definition of reflex |url=https://www.merriam-webster.com/dictionary/reflex |website=Dictionary by Merriam-Webster |date=25 December 2023 |language=en}}</ref>
[[File:Improved General Reflex Diagram.png|thumb|429x429px|The simplest reflex is initiated by a stimulus, which activates an afferent nerve. The signal is then passed to a response neuron, which generates a response.]]
Reflexes are found with varying levels of complexity in organisms with a [[nervous system]]. A reflex occurs via [[neural pathway]]s in the nervous system called [[reflex arc]]s. A stimulus initiates a neural signal, which is carried to a [[synapse]]. The signal is then transferred across the synapse to a [[motor neuron]], which evokes a target response. These neural signals do not always travel to the brain,<ref name=":02">{{Cite journal |date=2006-02-01 |title=Spinal reflexes, mechanisms and concepts: From Eccles to Lundberg and beyond |url=https://www.sciencedirect.com/science/article/pii/S0301008206000335 |journal=Progress in Neurobiology |language=en |volume=78 |issue=3–5 |pages=215–232 |doi=10.1016/j.pneurobio.2006.04.001 |issn=0301-0082|last1=Hultborn |first1=Hans |pmid=16716488 |s2cid=25904937 |url-access=subscription }}</ref> so many reflexes are an automatic response to a stimulus that does not receive or need conscious thought.<ref name="FD">{{cite web |title=tendon reflex |url=http://medical-dictionary.thefreedictionary.com/tendon+reflex |website=[[The Free Dictionary]]}}</ref>

Many reflexes are fine-tuned to increase organism survival and self-defense.<ref>{{Cite journal |last=Price |first=Joseph L. |date=2005-12-05 |title=Free will versus survival: Brain systems that underlie intrinsic constraints on behavior |journal=The Journal of Comparative Neurology |language=en |volume=493 |issue=1 |pages=132–139 |doi=10.1002/cne.20750 |pmid=16255003 |s2cid=18455906 |issn=0021-9967|doi-access=free }}</ref> This is observed in reflexes such as the [[Startle response|startle reflex]], which provides an automatic response to an unexpected stimulus, and the [[Cat righting reflex|feline righting reflex]], which reorients a cat's body when falling to ensure safe landing. The simplest type of reflex, a short-latency reflex, has a single synapse, or junction, in the signaling pathway.<ref>{{Cite book |last=Pierrot-Deseilligny |first=Emmanuel |title=The Circuitry of the Human Spinal Cord: Its Role in Motor Control and Movement Disorders |publisher=Cambridge University Press |year=2005 |isbn=978-0-511-54504-7}}</ref> Long-latency reflexes produce nerve signals that are transduced across multiple synapses before generating the reflex response.