Examine individual changes

'{{other uses|Reflex (disambiguation)}} {{redirect|Reflectory|the album by Pepper Adams|Reflectory (album)}} A '''reflex''', or '''reflex action''', is an involuntary and nearly instantaneous movement in response to a [[Stimulus (physiology)|stimulus]].<ref>Purves (2004). ''Neuroscience: Third Edition''. Massachusetts, Sinauer Associates, Inc.</ref><ref name="M-W">{{cite web|title=Definition of REFLEX|url=https://www.merriam-webster.com/dictionary/reflex|website=www.merriam-webster.com|language=en}}</ref> A reflex is made possible by [[neural pathway]]s called [[reflex arc]]s which can act on an impulse before that impulse reaches the brain. The reflex is then 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=TheFreeDictionary.com}}</ref> ==Human reflexes== '''Myotatic reflexes''' The [[stretch reflex|myotatic reflex]]es (also known as ''deep tendon reflexes''), provide information on the integrity of the [[central nervous system]] and [[peripheral nervous system]]. Generally, decreased reflexes indicate a peripheral problem, and lively or exaggerated reflexes a central one.{{Citation needed|date=December 2017}} A stretch reflex is the contraction of a muscle in response to its lengthwise stretch.<ref name="FD" /> * [[Biceps reflex]] ([[cervical spinal nerve 5|C5]], [[cervical spinal nerve 6|C6]]) * [[Brachioradialis reflex]] (C5, C6, [[cervical spinal nerve 7|C7]]) * [[Extensor digitorum reflex]] (C6, C7) * [[Triceps reflex]] (C6, C7, [[cervical spinal nerve 8|C8]]) * [[Patellar reflex]] or knee-jerk reflex ([[lumbar spinal nerve 2|L2]], [[lumbar spinal nerve 3|L3]], [[lumbar spinal nerve 4|L4]]) * [[Ankle jerk reflex]] (Achilles reflex) ([[sacral spinal nerve 1|S1]], [[sacral spinal nerve 2|S2]]) While the reflexes above are stimulated mechanically, the term [[H-reflex]] refers to the analogous reflex stimulated electrically, and [[tonic vibration reflex]] for those stimulated to vibration. ===Tendon reflex=== A [[tendon reflex]] is the contraction of a muscle in response to striking its tendon.<ref name="FD"/> The [[Golgi tendon reflex]] is the inverse of a stretch reflex. ===Reflexes involving cranial nerves=== {| class="wikitable" | '''Name''' || '''Sensory''' || '''Motor''' |- | [[Pupillary light reflex]] || II || III |- | [[Accommodation reflex]] || II || III |- | [[Jaw jerk reflex]] || V || V |- | [[Corneal reflex]], also known as the [[blink]] reflex || V || VII |- | [[Glabellar reflex]] || V || VII |- | [[Vestibulo-ocular reflex]] || VIII || III, IV, VI + |- | [[Gag reflex]] || IX || X |} ===Reflexes usually only observed in human infants=== {{main|Primitive reflexes}} [[Image:Greifreflex.JPG|thumb|Grasp reflex]]<!-- Deleted image removed: [[Image:Flexor Reflex.jpg|thumb|spinal cord]] --> [[Newborn babies]] have a number of other reflexes which are not seen in adults, referred to as '''primitive reflexes'''.<ref>{{Cite web|url=https://fpnotebook.com/Neuro/Exam/NrlgcExm.htm|title=Neurologic Exam|website=fpnotebook.com}}</ref> These automatic reactions to stimuli enable infants to respond to the environment before any learning has taken place. They include: * [[Asymmetrical tonic neck reflex]] (ATNR) * [[Palmomental reflex]] * [[Moro reflex]], also known as the startle reflex * [[Palmar grasp reflex]] * [[Primitive reflexes#Rooting reflex|Rooting reflex]] * [[Primitive reflexes#Sucking reflex|Sucking reflex]] * [[Symmetrical tonic neck reflex]] (STNR) * [[Tonic labyrinthine reflex]] (TLR) ===Other reflexes=== Other reflexes found in the central nervous system include: * [[Abdominal reflex]]es (T6-L1) **[[Gastrocolic reflex]] * [[Anal wink|Anocutaneous reflex]] (S2-S4) * [[Baroreflex]] * [[Cough reflex]] * [[Cremasteric reflex]] (L1-L2) * [[Diving reflex]] * [[Muscular defense]] * [[Photic sneeze reflex]] * [[Scratch reflex]] * [[Sneeze]] * [[Startle reflex]] * [[Withdrawal reflex]] **[[Crossed extensor reflex]] Many of these reflexes are quite complex requiring a number of synapses in a number of different nuclei in the [[Central nervous system|CNS]] (e.g., the [[escape reflex]]). Others of these involve just a couple of synapses to function (e.g., the [[withdrawal reflex]]). Processes such as [[breath]]ing, [[digestion]], and the maintenance of the [[Heart rate|heartbeat]] can also be regarded as reflex actions, according to some definitions of the term. ===Grading=== In [[medicine]], reflexes are often used to assess the health of the [[nervous system]]. [[physician|Doctors]] will typically grade the activity of a reflex on a scale from 0 to 4.<ref>[http://medinfo.ufl.edu/year1/bcs/clist/neuro.html University of Florida > Neurologic Examination] Retrieved on May 9, 2009</ref> While 2+ is considered normal, some healthy individuals are hypo-reflexive and register all reflexes at 1+, while others are hyper-reflexive and register all reflexes at 3+. {|class="wikitable" |Grade || Description |- | 0 || Absent |- | 1+ or + || Hypoactive |- | 2+ or ++ || "Normal" |- | 3+ or +++ || Hyperactive without [[clonus]] |- | 4+ or ++++ || Hyperactive with [[clonus]] |} ==See also== *[[List of reflexes (alphabetical)]] *[[All-or-none law]] *[[Automatic behavior]] *[[Conditioned reflex]] * [[Instinct]] * [[Jumping Frenchmen of Maine]] *[[Voluntary action]] *[[Preflexes]] ==References== {{reflist}} {{Nervous system physiology}} {{Reflex}} [[Category:Reflexes]] [[Category:Animal physiology]]'