WordNet

pull in opposite directions; "During the Inquisition, the torturers would stretch their victims on a rack"
extend ones limbs or muscles, or the entire body; "Stretch your legs!"; "Extend your right arm above your head" (同)extend
an unbroken period of time during which you do something; "there were stretches of boredom"; "he did a stretch in the federal penitentiary" (同)stint
extend ones body or limbs; "Lets stretch for a minute--weve been sitting here for over 3 hours" (同)stretch out
become longer by being stretched and pulled; "The fabric stretches"
the capacity for being stretched (同)stretchiness, stretchability
exercise designed to extend the limbs and muscles to their full extent (同)stretching
a straightaway section of a racetrack
extension to or beyond the ordinary limit; "running at full stretch"; "by no stretch of the imagination"; "beyond any stretch of his understanding"
a large and unbroken expanse or distance; "a stretch of highway"; "a stretch of clear water"
occupy a large, elongated area; "The park stretched beneath the train line" (同)stretch along
lie down comfortably; "To enjoy the picnic, we stretched out on the grass" (同)stretch out
easily stretched; "stretch hosiery"
extend the scope or meaning of; often unduly; "Stretch the limits"; "stretch my patience"; "stretch the imagination"
having an elongated seating area; "a stretch limousine"
an automatic instinctive unlearned reaction to a stimulus (同)reflex response, reflex action, instinctive reflex, innate reflex, inborn reflex, unconditioned_reflex, physiological reaction
extended or spread over a wide area or distance; "broad fields lay stretched on both sides of us"
(of muscles) relieved of stiffness by stretching; "well-stretched muscles are less susceptible to injury"
(of leaves) bent downward and outward more than 90 degrees
act of expanding by lengthening or widening

PrepTutorEJDIC

〈手足・翼など〉‘を'『いっぱいに伸ばす(広げる)』《+out+名,+名+out》 / 〈手など〉‘を'差し出す《+out+名,+名+out》 / (一方から一方へ)〈なわなど)‘を'張る,渡す,〈じゅうたんなど〉‘を'敷く《+名+out, out+名》 / 〈神経など〉‘を'極度に緊張させる,ぎりぎりまで使う(働かせる) / 〈意味・法律など〉‘を'拡大解釈する,誇張する / (無理に)〈靴など〉‘を'広げる,長くする,引っ張る / 〈訪問など〉‘を'引き延ばす,長びかせる / 〈人が〉『長々と横になる』(寝べる)《+out》 / 〈人が〉手足をいっぱいに克ばす《+out》 / 《副詞[句]を伴って》伸びている,広がっている / 〈ゴムなどが〉伸びる / 〈C〉(…の)(空間的な)『広がり』,伸び,範囲《+of+名》 / 〈C〉(時間的な)一続きの期間,長さ《+of+名》 / 〈C〉《単数形で》『伸ばす(伸びる)こと』 / 〈U〉弾力性,伸張力 / 〈C〉《単数形で》(競走路の,特に最後の)直線コース / 弾性を持つ材料でできた,ストレッチの
反射(刺激に対する無意識の反応) / 《複数形で》反射的な動き / (光などの)反射,反射光;映像 / 反射性の / (カメラが)レフ鋼の,反射型の

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/07/06 18:44:46」(JST)

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The stretch reflex (myotatic reflex) is a muscle contraction in response to stretching within the muscle. It is a monosynaptic reflex which provides automatic regulation of skeletal muscle length.

When a muscle lengthens, the muscle spindle is stretched and its nerve activity increases. This increases alpha motor neuron activity, causing the muscle fibers to contract and thus resist the stretching. A secondary set of neurons also causes the opposing muscle to relax. The reflex functions to maintain the muscle at a constant length.

Gamma motoneurons regulate how sensitive the stretch reflex is by tightening or relaxing the fibers within the spindle. There are several theories as to what may trigger gamma motoneurons to increase the reflex's sensitivity. For example, alpha-gamma co-activation might keep the spindles taut when a muscle is contracted, preserving stretch reflex sensitivity even as the muscle fibers become shorter. Otherwise the spindles would become slack and the reflex would cease to function.

This reflex has the shortest latency of all spinal reflexes including the Golgi tendon reflex and reflexes mediated by pain and cutaneous receptors.

Examples

A person standing upright begins to lean to one side. The postural muscles that are closely connected to the vertebral column on the side will stretch. Because of this, stretch receptors in those muscles contract to correct posture.

Other examples (followed by involved spinal nerves) are responses to stretch created by a blow upon a muscle tendon:

Jaw jerk reflex (CN V)
Biceps reflex C5/C6
Brachioradialis reflex C6
Extensor digitorum reflex C6/C7
Triceps reflex C7/C8
Patellar reflex L2-L4 (knee-jerk)
Ankle jerk reflex S1/S2

Another example is the group of fibers in the calf muscle, which synapse with motor neurons supplying muscle fibers in the same muscle. A sudden stretch, such as tapping the Achilles' tendon, causes a reflex contraction in the muscle as the spindles sense the stretch and send an action potential to the motor neurons which then cause the muscle to contract; this particular reflex causes a contraction in the soleus-gastrocnemius group of muscles. Like the patellar reflex, this reflex can be enhanced by the Jendrassik maneuver.

There are basically four types of muscle fibers. This includes the slow twitch (ST) fibers, which are slow contracting and slow to fatigue. The fast twitch muscle fibers are sub-divided into several sub-classes and include fibers that are fast contracting and resistant to fatigue (FRF), fast contracting but more easily fatigued (FEF), and fast contracting fast fatiguing white fibers (FFF). ^[1]

Supraspinal control

The central nervous system can influence the stretch reflex via the gamma motoneurons, which as described above control the sensitivity of the reflex.

Inhibitory signals arrive at gamma neurons through the lateral reticulospinal tract from Brodmann area 6, the paleocerebellum and the red nucleus. Facilitatory signals arrive through the ventral reticulospinal tract from Brodmann area 4, the neocerebellum and the vestibular nucleus.

Spinal control

Withdrawer reflex
Damping & Loading reflex
- Jendrassik maneuver

Pathology

Grading of stretch reflexes upon tapping muscle tendon^[2]
Grade	Response	Significance
0	no response	always abnormal
1+	slight but definitely present response	may or may not be normal
2+	brisk response	normal
3+	very brisk response	may or may not be normal
4+	clonus	always abnormal

The clasp-knife response is a stretch reflex with a rapid decrease in resistance when attempting to flex a joint. It is one of the characteristic responses of an upper motor neuron lesion.

References

^ Dr. Michael Yessis (2000). Explosive Running. McGraw-Hill Companies, Inc.; 1st edition. ISBN 978-0809298990.
^ Walker, H. K.; Walker, H. K.; Hall, W. D.; Hurst, J. W. (1990). "Deep Tendon Reflexes". PMID 21250237. edit [1]

External links

Reflex, Stretch at the US National Library of Medicine Medical Subject Headings (MeSH)
"Stretch reflex" at Dorland's Medical Dictionary

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 神経伝導検査：応答遅延 nerve conduction studies late responses
2. 幼児および小児における精密な神経学的評価 detailed neurologic assessment of infants and children
3. 過負荷による（慢性）腱障害のマネージメントの概要 overview of the management of overuse chronic tendinopathy
4. 先天性筋性斜頚 congenital muscular torticollis
5. 下肢ランニング障害の概要 overview of running injuries of the lower extremity

English Journal

Effects of neuromuscular function and split step on reaction speed in simulated tennis response.

Nieminen MJ1, Piirainen JM, Salmi JA, Linnamo V.
European journal of sport science.Eur J Sport Sci.2014 Jun;14(4):318-26. doi: 10.1080/17461391.2013.785598. Epub 2013 Apr 20.
Abstract The purpose of this study was to examine whether split step (small hop before step) would be more beneficial than no-split condition in simulated tennis response situation. In addition, it was studied if movement time of the response is related to separately measured force production capabi
PMID 23600926

Effect of mental fatigue on induced tremor in human knee extensors.

Budini F1, Lowery M2, Durbaba R3, De Vito G4.
Journal of electromyography and kinesiology : official journal of the International Society of Electrophysiological Kinesiology.J Electromyogr Kinesiol.2014 Jun;24(3):412-8. doi: 10.1016/j.jelekin.2014.02.003. Epub 2014 Feb 20.
In this study, the effects of mental fatigue on mechanically induced tremor at both a low (3-6Hz) and high (8-12Hz) frequency were investigated. The two distinct tremor frequencies were evoked using two springs of different stiffness, during 20s sustained contractions of the knee extensor muscles at
PMID 24613661

Changes in soleus H-reflex during walking in middle-aged healthy subjects.

Raffalt PC1, Alkjaer T, Simonsen EB.
Muscle & nerve.Muscle Nerve.2014 May 6. doi: 10.1002/mus.24279. [Epub ahead of print]
Introduction: To explore the effect of aging on stretch reflex modulation during walking, soleus H-reflexes obtained in 15 middle-aged (mean age 56.4 ± 6.9) and 15 young (mean age 23.7 ± 3.9) subjects were compared. Methods: The H-reflex amplitude, muscle activity (EMG) of the soleus and tibialis
PMID 24801567