In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action[1] and nearly instantaneous response to a stimulus.[2][3]
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 pathways in the nervous system called reflex arcs. 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,[4] so many reflexes are an automatic response to a stimulus that does not receive or need conscious thought.[5]
Many reflexes are fine-tuned to increase organism survival and self-defense.[6] This is observed in reflexes such as the startle reflex, which provides an automatic response to an unexpected stimuli, and the 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.[7] Long-latency reflexes produce nerve signals that are transduced across multiple synapses before generating the reflex response.
The myotatic or muscle stretch reflexes (sometimes known as deep tendon reflexes) provide information on the integrity of the central nervous system and peripheral nervous system. This information can be detected using electromyography (EMG).[8] Generally, decreased reflexes indicate a peripheral problem, and lively or exaggerated reflexes a central one.[8] A stretch reflex is the contraction of a muscle in response to its lengthwise stretch.
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. The Golgi tendon reflex is the inverse of a stretch reflex.
Newborn babies have a number of other reflexes which are not seen in adults, referred to as primitive reflexes. These automatic reactions to stimuli enable infants to respond to the environment before any learning has taken place. They include:
Many of these reflexes are quite complex requiring a number of synapses in a number of different nuclei in the 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 breathing, digestion, and the maintenance of the 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. Doctors will typically grade the activity of a reflex on a scale from 0 to 4. 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+.
Grade
Description
0
Absent ("mute")
1+ or +
Hypoactive
2+ or ++
"Normal"
3+ or +++
Hyperactive withoutclonus, with spread to adjacent muscle groups
An example of reflex reversal is depicted. Activating the same spinal reflex pathway can cause limb flexion while standing, and extension while walking.
Naively, we might imagine that reflexes are immutable. In reality, however, most reflexes are flexible and can be substantially modified to match the requirements of the behavior in both vertebrates and invertebrates.[9][10][11]
A good example of reflex modulation is the stretch reflex.[12][13][14][15] When a muscle is stretched at rest, the stretch reflex leads to contraction of the muscle, thereby opposing stretch (resistance reflex). This helps to stabilize posture. During voluntary movements, however, the intensity (gain) of the reflex is reduced or its sign is even reversed. This prevents resistance reflexes from impeding movements.
The underlying sites and mechanisms of reflex modulation are not fully understood. There is evidence that the output of sensory neurons is directly modulated during behavior—for example, through presynaptic inhibition.[16][17] The effect of sensory input upon motor neurons is also influenced by interneurons in the spinal cord or ventral nerve cord[15] and by descending signals from the brain.[18][19][20]
^parveen (November 11, 2020). "Reflex action". Definition, Types and Mechanism and Important solved questions. Crack Your Target. Retrieved 3 April 2021.
^Purves (2004). Neuroscience: Third Edition. Massachusetts, Sinauer Associates, Inc.
^Hultborn, Hans (2006-02-01). "Spinal reflexes, mechanisms and concepts: From Eccles to Lundberg and beyond". Progress in Neurobiology. 78 (3–5): 215–232. doi:10.1016/j.pneurobio.2006.04.001. ISSN 0301-0082. PMID 16716488. S2CID 25904937.
^Price, Joseph L. (2005-12-05). "Free will versus survival: Brain systems that underlie intrinsic constraints on behavior". The Journal of Comparative Neurology. 493 (1): 132–139. doi:10.1002/cne.20750. ISSN 0021-9967. PMID 16255003. S2CID 18455906.
^Pierrot-Deseilligny, Emmanuel (2005). The Circuitry of the Human Spinal Cord: Its Role in Motor Control and Movement Disorders. Cambridge University Press. ISBN9780511545047.
^Pearson KG (1993). "Common principles of motor control in vertebrates and invertebrates". Annual Review of Neuroscience. 16: 265–97. doi:10.1146/annurev.ne.16.030193.001405. PMID 8460894.
^Büschges A, Manira AE (December 1998). "Sensory pathways and their modulation in the control of locomotion". Current Opinion in Neurobiology. 8 (6): 733–9. doi:10.1016/S0959-4388(98)80115-3. PMID 9914236. S2CID 18521928.
^Tuthill JC, Azim E (March 2018). "Proprioception". Current Biology. 28 (5): R194–R203. doi:10.1016/j.cub.2018.01.064. PMID 29510103. S2CID 235330764.
^Bässler U (March 1976). "Reversal of a reflex to a single motoneuron in the stick insect Çarausius morosus". Biological Cybernetics. 24 (1): 47–49. doi:10.1007/BF00365594. ISSN 1432-0770. S2CID 12007820.
^Forssberg H, Grillner S, Rossignol S (August 1977). "Phasic gain control of reflexes from the dorsum of the paw during spinal locomotion". Brain Research. 132 (1): 121–39. doi:10.1016/0006-8993(77)90710-7. PMID 890471. S2CID 32578292.
^Capaday C, Stein RB (May 1986). "Amplitude modulation of the soleus H-reflex in the human during walking and standing". The Journal of Neuroscience. 6 (5): 1308–13. doi:10.1523/JNEUROSCI.06-05-01308.1986. PMC6568550. PMID 3711981.
^ abClarac F, Cattaert D, Le Ray D (May 2000). "Central control components of a 'simple' stretch reflex" (PDF). Trends in Neurosciences. 23 (5): 199–208. doi:10.1016/s0166-2236(99)01535-0. PMID 10782125. S2CID 10113723.
^Wolf H, Burrows M (August 1995). "Proprioceptive sensory neurons of a locust leg receive rhythmic presynpatic inhibition during walking". The Journal of Neuroscience. 15 (8): 5623–36. doi:10.1523/JNEUROSCI.15-08-05623.1995. PMC6577635. PMID 7643206.
^Sauer AE, Büschges A, Stein W (April 1997). "Role of presynaptic inputs to proprioceptive afferents in tuning sensorimotor pathways of an insect joint control network". Journal of Neurobiology. 32 (4): 359–76. doi:10.1002/(SICI)1097-4695(199704)32:4<359::AID-NEU1>3.0.CO;2-5. PMID 9087889.
^Mu L, Ritzmann RE (December 20, 2007). "Interaction between descending input and thoracic reflexes for joint coordination in cockroach: I. descending influence on thoracic sensory reflexes". Journal of Comparative Physiology A. 194 (3): 283–98. doi:10.1007/s00359-007-0307-x. PMID 18094976. S2CID 25167774.
^Martin JP, Guo P, Mu L, Harley CM, Ritzmann RE (November 2015). "Central-complex control of movement in the freely walking cockroach". Current Biology. 25 (21): 2795–2803. doi:10.1016/j.cub.2015.09.044. PMID 26592340.
^Hsu LJ, Zelenin PV, Orlovsky GN, Deliagina TG (February 2017). "Supraspinal control of spinal reflex responses to body bending during different behaviours in lampreys". The Journal of Physiology. 595 (3): 883–900. doi:10.1113/JP272714. PMC5285725. PMID 27589479.
^Park, Hyeong-Dong; Barnoud, Coline; Trang, Henri; Kannape, Oliver A.; Schaller, Karl; Blanke, Olaf (February 6, 2020). "Breathing is coupled with voluntary action and the cortical readiness potential". Nature Communications. Nature Portfolio. 11 (1): 289. Bibcode:2020NatCo..11..289P. doi:10.1038/s41467-019-13967-9. ISSN 2041-1723. PMC7005287. PMID 32029711.
^"21.10B: Neural Mechanisms (Cortex)". Medicine LibreTexts. 2018-07-22. Retrieved 2022-09-10.
March 08, 2023
reflex, other, uses, disambiguation, reflectory, redirects, here, album, reflectory, album, this, article, written, from, excessively, human, centric, perspective, please, improve, this, article, that, appropriately, covers, human, species, discuss, this, issu. For other uses see Reflex disambiguation Reflectory redirects here For the album see Reflectory album This article may be written from an excessively human centric perspective Please improve this article so that it appropriately covers non human species or discuss this issue on the talk page September 2022 Learn how and when to remove this template message In biology a reflex or reflex action is an involuntary unplanned sequence or action 1 and nearly instantaneous response to a stimulus 2 3 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 pathways in the nervous system called reflex arcs 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 4 so many reflexes are an automatic response to a stimulus that does not receive or need conscious thought 5 Many reflexes are fine tuned to increase organism survival and self defense 6 This is observed in reflexes such as the startle reflex which provides an automatic response to an unexpected stimuli and the 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 7 Long latency reflexes produce nerve signals that are transduced across multiple synapses before generating the reflex response Contents 1 Types of human reflexes 1 1 Myotatic reflexes 1 2 Tendon reflex 1 3 Reflexes involving cranial nerves 1 4 Reflexes usually only observed in human infants 1 5 Other kinds of reflexes 1 6 Grading 2 Reflex modulation 3 Other reflexes 4 See also 5 ReferencesTypes of human reflexes EditMyotatic reflexes Edit The myotatic or muscle stretch reflexes sometimes known as deep tendon reflexes provide information on the integrity of the central nervous system and peripheral nervous system This information can be detected using electromyography EMG 8 Generally decreased reflexes indicate a peripheral problem and lively or exaggerated reflexes a central one 8 A stretch reflex is the contraction of a muscle in response to its lengthwise stretch Biceps reflex C5 C6 Brachioradialis reflex C5 C6 C7 Extensor digitorum reflex C6 C7 Triceps reflex C6 C7 C8 Patellar reflex or knee jerk reflex L2 L3 L4 Ankle jerk reflex Achilles reflex S1 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 Edit A tendon reflex is the contraction of a muscle in response to striking its tendon The Golgi tendon reflex is the inverse of a stretch reflex Reflexes involving cranial nerves Edit Name Sensory MotorPupillary light reflex II IIIAccommodation reflex II IIIJaw jerk reflex V VCorneal reflex also known as the blink reflex V VIIGlabellar reflex V VIIVestibulo ocular reflex VIII III IV VI Gag reflex IX XReflexes usually only observed in human infants Edit Main article Primitive reflexes Grasp reflex Newborn babies have a number of other reflexes which are not seen in adults referred to as primitive reflexes 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 Rooting reflex Sucking reflex Symmetrical tonic neck reflex STNR Tonic labyrinthine reflex TLR Other kinds of reflexes Edit Other reflexes found in the central nervous system include Abdominal reflexes T6 L1 Gastrocolic reflex Anocutaneous reflex S2 S4 Baroreflex Cough reflex Cremasteric reflex L1 L2 Diving reflex Lazarus sign Muscular defense Photic sneeze reflex Scratch reflex Sneeze Startle reflex Withdrawal reflex Crossed extensor reflexMany of these reflexes are quite complex requiring a number of synapses in a number of different nuclei in the 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 breathing digestion and the maintenance of the heartbeat can also be regarded as reflex actions according to some definitions of the term Grading Edit In medicine reflexes are often used to assess the health of the nervous system Doctors will typically grade the activity of a reflex on a scale from 0 to 4 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 Grade Description0 Absent mute 1 or Hypoactive2 or Normal 3 or Hyperactive without clonus with spread to adjacent muscle groups4 or Hyperactive with clonusReflex modulation Edit An example of reflex reversal is depicted Activating the same spinal reflex pathway can cause limb flexion while standing and extension while walking Naively we might imagine that reflexes are immutable In reality however most reflexes are flexible and can be substantially modified to match the requirements of the behavior in both vertebrates and invertebrates 9 10 11 A good example of reflex modulation is the stretch reflex 12 13 14 15 When a muscle is stretched at rest the stretch reflex leads to contraction of the muscle thereby opposing stretch resistance reflex This helps to stabilize posture During voluntary movements however the intensity gain of the reflex is reduced or its sign is even reversed This prevents resistance reflexes from impeding movements The underlying sites and mechanisms of reflex modulation are not fully understood There is evidence that the output of sensory neurons is directly modulated during behavior for example through presynaptic inhibition 16 17 The effect of sensory input upon motor neurons is also influenced by interneurons in the spinal cord or ventral nerve cord 15 and by descending signals from the brain 18 19 20 Other reflexes EditBreathing can also be considered both involuntary and voluntary since breath can be held through internal intercostal muscles 21 22 23 See also EditAll or none law Automatic behavior Conditioned reflex Instinct Jumping Frenchmen of Maine List of reflexes alphabetical Preflexes Voluntary actionReferences Edit parveen November 11 2020 Reflex action Definition Types and Mechanism and Important solved questions Crack Your Target Retrieved 3 April 2021 Purves 2004 Neuroscience Third Edition Massachusetts Sinauer Associates Inc Definition of REFLEX www merriam webster com Hultborn Hans 2006 02 01 Spinal reflexes mechanisms and concepts From Eccles to Lundberg and beyond Progress in Neurobiology 78 3 5 215 232 doi 10 1016 j pneurobio 2006 04 001 ISSN 0301 0082 PMID 16716488 S2CID 25904937 tendon reflex TheFreeDictionary com Price Joseph L 2005 12 05 Free will versus survival Brain systems that underlie intrinsic constraints on behavior The Journal of Comparative Neurology 493 1 132 139 doi 10 1002 cne 20750 ISSN 0021 9967 PMID 16255003 S2CID 18455906 Pierrot Deseilligny Emmanuel 2005 The Circuitry of the Human Spinal Cord Its Role in Motor Control and Movement Disorders Cambridge University Press ISBN 9780511545047 a b Tsuji Hironori Misawa Haruo Takigawa Tomoyuki Tetsunaga Tomoko Yamane Kentaro Oda Yoshiaki Ozaki Toshifumi 2021 01 27 Quantification of patellar tendon reflex using portable mechanomyography and electromyography devices Scientific Reports 11 1 2284 doi 10 1038 s41598 021 81874 5 ISSN 2045 2322 PMC 7840930 PMID 33504836 Pearson KG 1993 Common principles of motor control in vertebrates and invertebrates Annual Review of Neuroscience 16 265 97 doi 10 1146 annurev ne 16 030193 001405 PMID 8460894 Buschges A Manira AE December 1998 Sensory pathways and their modulation in the control of locomotion Current Opinion in Neurobiology 8 6 733 9 doi 10 1016 S0959 4388 98 80115 3 PMID 9914236 S2CID 18521928 Tuthill JC Azim E March 2018 Proprioception Current Biology 28 5 R194 R203 doi 10 1016 j cub 2018 01 064 PMID 29510103 S2CID 235330764 Bassler U March 1976 Reversal of a reflex to a single motoneuron in the stick insect Carausius morosus Biological Cybernetics 24 1 47 49 doi 10 1007 BF00365594 ISSN 1432 0770 S2CID 12007820 Forssberg H Grillner S Rossignol S August 1977 Phasic gain control of reflexes from the dorsum of the paw during spinal locomotion Brain Research 132 1 121 39 doi 10 1016 0006 8993 77 90710 7 PMID 890471 S2CID 32578292 Capaday C Stein RB May 1986 Amplitude modulation of the soleus H reflex in the human during walking and standing The Journal of Neuroscience 6 5 1308 13 doi 10 1523 JNEUROSCI 06 05 01308 1986 PMC 6568550 PMID 3711981 a b Clarac F Cattaert D Le Ray D May 2000 Central control components of a simple stretch reflex PDF Trends in Neurosciences 23 5 199 208 doi 10 1016 s0166 2236 99 01535 0 PMID 10782125 S2CID 10113723 Wolf H Burrows M August 1995 Proprioceptive sensory neurons of a locust leg receive rhythmic presynpatic inhibition during walking The Journal of Neuroscience 15 8 5623 36 doi 10 1523 JNEUROSCI 15 08 05623 1995 PMC 6577635 PMID 7643206 Sauer AE Buschges A Stein W April 1997 Role of presynaptic inputs to proprioceptive afferents in tuning sensorimotor pathways of an insect joint control network Journal of Neurobiology 32 4 359 76 doi 10 1002 SICI 1097 4695 199704 32 4 lt 359 AID NEU1 gt 3 0 CO 2 5 PMID 9087889 Mu L Ritzmann RE December 20 2007 Interaction between descending input and thoracic reflexes for joint coordination in cockroach I descending influence on thoracic sensory reflexes Journal of Comparative Physiology A 194 3 283 98 doi 10 1007 s00359 007 0307 x PMID 18094976 S2CID 25167774 Martin JP Guo P Mu L Harley CM Ritzmann RE November 2015 Central complex control of movement in the freely walking cockroach Current Biology 25 21 2795 2803 doi 10 1016 j cub 2015 09 044 PMID 26592340 Hsu LJ Zelenin PV Orlovsky GN Deliagina TG February 2017 Supraspinal control of spinal reflex responses to body bending during different behaviours in lampreys The Journal of Physiology 595 3 883 900 doi 10 1113 JP272714 PMC 5285725 PMID 27589479 Mitchell R A Berger A J February 1975 Neural regulation of respiration The American Review of Respiratory Disease American Thoracic Society 111 2 206 224 doi 10 1164 arrd 1975 111 2 206 inactive 31 December 2022 ISSN 0003 0805 PMID 1089375 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint DOI inactive as of December 2022 link Park Hyeong Dong Barnoud Coline Trang Henri Kannape Oliver A Schaller Karl Blanke Olaf February 6 2020 Breathing is coupled with voluntary action and the cortical readiness potential Nature Communications Nature Portfolio 11 1 289 Bibcode 2020NatCo 11 289P doi 10 1038 s41467 019 13967 9 ISSN 2041 1723 PMC 7005287 PMID 32029711 21 10B Neural Mechanisms Cortex Medicine LibreTexts 2018 07 22 Retrieved 2022 09 10 Retrieved from https en wikipedia org w index php title Reflex amp oldid 1130884127, wikipedia, wiki, book, books, library,
