Editing Withdrawal reflex

{{Short description|Spinal reflex}}
The '''withdrawal reflex''' ('''nociceptive flexion reflex''' or '''flexor withdrawal reflex''') is a [[spinal reflex]] intended to protect the body from damaging stimuli.<ref name="soscad">{{cite book |last1=Solomon |last2=Schmidt |editor1-first=Field |editor1-last=Carol |title=Human Anatomy & physiology |edition=2 |year=1990 |publisher=Saunders College Publishing |isbn=0-03-011914-6 |page=[https://archive.org/details/humananatomyphys00solo/page/470 470] |chapter=13 |chapter-url-access=registration |chapter-url=https://archive.org/details/humananatomyphys00solo/page/470 }}</ref>  The reflex rapidly coordinates the contractions of all the flexor muscles and the relaxations of the extensors in that limb causing sudden withdrawal from the potentially damaging stimulus.<ref name=PearsonGordon2013-p792>{{harvp | Pearson | Gordon | 2013 | loc = Cutaneous Reflexes Produce Complex Movements That Serve Protective and Postural Functions, p. 792 }}</ref> Spinal reflexes are often monosynaptic and are mediated by a simple [[reflex arc]]. A withdrawal [[reflex]] is mediated by a [[reflex arc|polysynaptic reflex]] resulting in the stimulation of many motor neurons in order to give a quick response.<ref name="Martin">{{cite book|last1=Martin|first1=Elizabeth|title=A dictionary of biology|date=2008|publisher=Oxford University Press|location=Oxford|isbn=978-019-920462-5|page=519|edition=6th}}</ref>

==Example==
When a person touches a hot object and withdraws their hand from it without actively thinking about it, the heat stimulates [[Thermoreceptor|temperature]] and [[Nociceptor|pain receptors]] in the skin, triggering a sensory impulse that travels to the [[central nervous system]]. The sensory neuron then [[synapse]]s with [[spinal interneuron|interneuron]]s that connect to motor [[neuron]]s.<ref name="thpa">{{cite book |last1=Thibodeau |first1=Gary |last2=Patton |first2=Kevin  |editor1-first=Sally|editor1-last=Schrefer |title=Structure & Function of the Body |url=https://archive.org/details/structurefunctio0011thib |url-access=registration |edition=11 |year=2000 |publisher=Mosby, Inc |isbn=0-323-01082-2 |page=[https://archive.org/details/structurefunctio0011thib/page/170 170] |chapter=7}}</ref> Some of these send motor impulses to the [[flexor]]s that lead to the muscles in the arm to contract, while some motor neurons send inhibitory impulses to the extensors so [[flexion]] is not inhibited. This is referred to as [[reciprocal innervation]].<ref name="sestta">{{cite book |last1=Seeley |first1=Rod |last2=Stephens |first2=Trent |author3=Philip Tate |editor1-first=Deborah |editor1-last=Allen |title=Anatomy and physiology |edition=2 |year=1992 |publisher=Mosby-Year Book, Inc}}</ref>

The withdrawal reflex in the leg can be examined and measured, using an [[electromyogram]] to monitor the muscle activity in the upper leg ([[biceps femoris muscle |biceps femoris]]) while applying increasing electrical stimulation to the lower leg ([[sural nerve]]) on the same side of the body. The stimulus intensity at which the reflex is evoked is often the intensity at which the subject reports the onset of pain, and the strength of the withdrawal reflex is correlated with the strength of the pain experienced.<ref name = Rhudy&France>{{cite journal |author=Rhudy JL, France CR |title=Defining the nociceptive flexion reflex (NFR) threshold in human participants: a comparison of different scoring criteria |journal=Pain |volume=128 |issue=3 |pages=244–53 |date=April 2007 |pmid=17070999 |pmc=1993909 |doi=10.1016/j.pain.2006.09.024 }}</ref>

==Crossed extension reflex following withdrawal reflex==
{{main|Crossed extensor reflex}}
Once a danger receptor (called "nociceptor") has been stimulated, the signal travels via the sensory nerve to the dorsal (posterior) horn of the spinal cord. The nerve synapses with ipsilateral motor neurons that exit the ventral (anterior) horn of the spinal cord and work to pull the soon-to-be injured body part away from danger within 0.5 seconds.<ref name="soscad" /> At the same time, the sensory neuron synapses with the ipsilateral motor neuron, as well as the motor neuron in the contralateral anterior horn.<ref name="sestta" /> This motor neuron stabilizes the uninjured side of the body (for instance; preparing the other leg to support the entire body weight when the other foot has stepped on a tack). At the same time as these two synapses, the sensory neuron also sends signals along the spinal cord to get motor neurons to contract muscles that shift the center of gravity of the body to maintain balance. This contralateral stimulation of motor neurons to stabilize the body is called the crossed extension reflex, and is a result of the withdrawal reflex (usually in the lower extremities).<ref>{{cite book | last1 = Saladin | first1 = KS | year = 2018 | title = Anatomy and Physiology: The Unity of Form and Function | edition = 8th | location = New York | publisher = McGraw-Hill | isbn = 978-1-259-27772-6 | chapter = Chapter 13 - The Spinal Cord, Spinal Nerves, and Somatic Reflexes | at = The Crossed Extension Reflex, p. 498}}</ref>

==See also==
*[[Interneuron]]
*[[Nociceptor]]
*[[Reflex]]

==References==
<references />

=== Other references ===
* {{cite book | last1 = Pearson | first1 = Keir G | last2 = Gordon | first2 = James E | year = 2013 | title = Principles of Neural Science | edition = 5th | editor-last1 = Kandel | editor-first1 = Eric R | editor-last2 = Schwartz | editor-first2 = James H | editor-last3 = Jessell | editor-first3 = Thomas M | editor-last4 = Siegelbaum | editor-first4 = Steven A | editor-last5 = Hudspeth | editor-first5 = AJ | location = United States | publisher = McGraw-Hill | isbn = 978-0-07-139011-8 | chapter = 35 - Spinal Reflexes }}

==External links==
*[http://www.smi.auc.dk/~oka/phdsum.html Ole K. Andersen, SMI, Aalborg University - Physiological and Pharmacological modulation of the human nociceptive withdrawal reflex] {{Webarchive|url=https://web.archive.org/web/20040811142511/http://www.smi.auc.dk/~oka/phdsum.html |date=2004-08-11 }}

{{Reflex}}

[[Category:Reflexes]]