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Title: Muscle Spindle and postural tone

Headings:  The muscle spindle’s anatomy and its role in posture

Introduction
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The muscle spindle has been widely studied and investigated for many years. Hassal (1851) was on getting rid of hemorrhoids
 e of the first people who discussed the muscle spindle as a thin fiber the body’s skeletal muscle. In 1963, Kuhne labeled the structure as muskelspindeln because of its fusiform in shape. Onanoff (1890) uses rhizotomy to prove the existence of sensory and motor nerves at the muscle spindle. Sherrington (1894) has linked those special fibers within the muscle spindle as intrafusal fibers. He was also able to discuss the periaxial space between the mass of intrafusal fibers and connective tissue capsule.
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Ruffini (1897) discussed and labeled the different nerve endings located at the muscle spindle. The mid equatorial region of muscle spindle is labeled as annulospiral or primary endings, flowerspray or secondary in the myo-tubular region, and plate endings at the poles of the fibers.
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In the 20th century, more and more research has been conducted to discuss the role of the muscle spindle in our body. Boyd (1956) together with Cooper and Daniel (1963) has separated the intrafusal fiber into nuclear chain and nuclear bag fibers located at deep muscles of neck and lumbrical muscles in human. Other researches such as Kuffler, Hunt, and Quillian (1951) and Leskell (1945) have shown that muscle spindle derives their motor supply from small motor fibers such as fusimotor or gamma fibers. getting rid of hemorrhoids


Another experiment that tests the muscle spindle was performed by Adal, getting rid of hemorrhoids
Barker and Stacey in 1970. They further classified the motor endings into trail and plate endings. The muscle spindle was also discussed as highly sensitive stretch receptors and its structural division into nuclear chain and nuclear bag fibers. The nuclear chain fibers are static and slow adaptive in nature while the nuclear bag fibers are responsible for recognizing velocity and position of a dynamic response in nature.

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Overview
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The muscle spindle is a thin and long structure located parallel and adjacent to muscle fibers. It is composed of several components that have efferent and afferent innervations. The muscle spindle functions as stretch receptor and reacts to dynamic and static changes of the skeletal muscles.  On other words, the muscle spindle recognizes the tension of our muscle in order to monitor and regulate its posture, tone and accuracy of movements.
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The muscle spindle is a proprioceptor that is found within our skeletal muscles. This paper reviews the anatomy and physiology of the muscle spindle and its role in posture and movement. The major features of their structure, innervations, and function are also discussed.

Function  
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The sensory nerve endings of the muscle spindles are responsible in relaying messages and information to the spinal cord whenever they are stimulated by the intrafusal fibers’ contraction. This type of contraction can arise by stretching the environment of extrafusal fibers or by motor stimulation via gamma efferent fibers. The information to the spinal cord is conducted by either the Group Ia or Group II afferent fibers. The afferent neurons are joined with alpha motor neurons which bring out the contraction of functional muscle or extrafusal muscle fibers, thus regulating the tone, accuracy of fine movements, and posture.
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Ritson (1982) has discussed that the postural stability is the ability of the control system to maintain the particular part of the body steady. Once the muscles are stretch and extends through out the sensory endings of the muscle spindles, it results as an increase of afferent input of afferent nerve fibers. The capacity of the muscle to oppose extension is known as a stretch reflex. The modification of the stretch reflex is a result from the inhibitory and excitatory impulses from the brain to the spinal cord, thus becoming the basis of posture and voluntary movement.
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In addition, the muscle spindles are involved in the reflex pathways within the motor centers to the brainstem. The messages are transmitted from the muscle spindles to the automatic motor control center as seen in the level of consciousness, thus contributing to the appreciation of limb position and movement.

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If the dynamic bag 1 fiber is activated, the spindle primary endings become over sensitive to changes during movement. There will be an increase in gain of the stretch reflex during movement. The increase in gain of the stretch reflex will decrease once the muscle reaches its final getting rid of hemorrhoids
position. Such a process can be used to produce an antagonist muscle during muscle movement, but the contrasting forces would be decline when the muscles’ final position is reached. Poorly controlled movement may occur if there is unopposed contraction of the agonist muscle which can overshoot the final desired position.
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On the other hand, if the static dynamic bag fiber is activated, the signal from the muscle spindles and the force coming from the muscles are both increased. However, there may be a slight variation with the gain of stretch reflex. In addition, if the nuclear chain fiber is activated, it can reduce the effectiveness of the muscle spindle as a mechanism of measuring length.

Types

Physical Features getting rid of hemorrhoids

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Merilles (1960) stated that the outer capsule which surrounds the intrafusal tubules are made of cells which are known as fibroblast and collagen fibers. On the other hand, the inner capsule is also made up of fibroblast but it is more delicate and it envelops each intrafusal fibers. The cells have shown small vesicles thus implicating the essential role of capsule in transport. The outer capsule’s space is rich in fluid such as hyaluronic acids getting rid of hemorrhoids

Motor Endings

• Plate endings
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Plate endings are divided into two groups, P2 or classical plate endings and P1 Plate endings. The P2 or classical plate endings are located on nuclear chain fibers and nuclear bag. It occurs at the spinal cord region once they are stimulated by intrafusal fiber contraction. On the other hand, the P1 plate endings have been located at the extreme poles of nuclear bag fibers only. The Beta fibers serve as the collateral of alpha nerves by supplying intrafusal muscle fibers.