Mechanisms underlying acute changes in range of motion
David G. Behm in The Science and Physiology of Flexibility and Stretching, 2018
Proprioceptive neuromuscular facilitation (PNF) stretching uses many of the inhibitory mechanisms, whereas dynamic stretching tends to excite rather than inhibit spindle reflexes. S. Peter Magnusson, a well-respected stretch researcher from Denmark, indicated that the acute effects of stretching in the holding phase of a stretch are due to changes in tissue viscoelasticity. In terms of movement, the antagonist inhibition is efficient because it automatically reduces muscle contractions that work in opposition to the intended motion. There are a number of other explanations for the increased range of motion immediately after stretching. Depending on whether the stretching is static, PNF, or dynamic, there may be various emphases on whether it is thixotropic, neural, mechanical, or psychological. A receptor that is activated by tension exerted on the muscle tendon and muscle is the Golgi tendon organ (GTO). Together with the GTO inhibition to large amplitude stretches, the Renshaw cells can also play a minor role with large amplitude stretches.
Sensory contributions to control
Andrea Utley in Motor Control, Learning and Development, 2018
This chapter describes four different proprioceptors: the muscle spindle, Golgi tendon organs, the vestibular apparatus and joint receptors. Muscle spindles are found in most skeletal muscles but are particularly concentrated in muscles that exert fine motor control. Vision and visual information is the most important source of sensory information. Interception tasks have attracted considerable attention, as they provide a good opportunity to study the complex interactions between human motor control processes and the dynamic environment in which we live. The chapter outlines the role of sensory information for control and coordination and covers a range of fascinating research which, over the years, has revealed how we are able to do so in complex and diverse movement contexts. Anticipation is a strategy used by athletes to reduce the time they take to respond to a stimulus.
Skeletal Muscle
Nassir H. Sabah in Neuromuscular Fundamentals, 2020
A skeletal muscle consists of muscle fibers comprising mainly myosin thick filaments and actin thin filaments. A contractile force is generated through sliding of these filaments, with respect to one another, as a result of cross-bridge cycling in the presence of a high concentration of calcium ions. This concentration increases because of a massive influx from the terminal cisternae caused by the depolarization of the muscle action potential but is quickly restored to normal by an efficient ion pump. The muscle fibers of a motor unit are all innervated by one motoneuron and belong to one of three types of fiber: Type I, Type IIA, or Type IIB, which differ in their speed of contraction and their resistance to fatigue. The arrangement of muscle fibers in a muscle results in four types of muscle: parallel, convergent, pennate, or sphincter muscles. There are three types of receptors in skeletal muscle: Golgi tendon organs that respond to the force of contraction, secondary muscle spindle receptors that respond to the amount of stretch, and primary muscle spindle receptors that respond to amount of stretch and its rate of change. The muscle spindle receptors are on intrafusal muscle fibers innervated by γ-motoneurons.
Proprioception in the Extraocular Muscles of Mammals and Man
Published in Strabismus, 2006
Roland Blumer, Kadriye Zeynep Konacki, Johannes Streicher, Wolfram Hoetzenecker, Michael Josef Franz Blumer, Julius-Robert Lukas
This article summarizes the authors' previous studies on proprioceptors in extraocular muscles (EOMs) of mammals and man. They report on muscle spindles in the EOMs of man, Golgi tendon organs in the EOMs of even-toed ungulates, and palisade endings in the EOMs of the cat. Muscle spindles: Muscle spindles are present in the EOMs of some mammals and in the EOMs of man. Compared with muscle spindles in other skeletal muscles, those in human EOMs exhibit structural differences. These structural differences may indicate a special function. Golgi tendon organs: Golgi tendon organs are absent in human EOMs. Golgi tendon organs exhibiting a specific morphology are present in the EOMs of even-toed ungulates. Their high number and rich innervation indicate functional importance. Palisade endings: Palisade endings are nervous end organs confined to the EOMs of mammals and man. It is assumed that these organs have a proprioceptive function. The authors show that palisade endings are immunoreactive for antibodies against choline acetyltransferase. Neuromuscular contacts, if present in palisade endings, are α -bungarotoxin positive as well. Taken together, these results show that palisade endings exhibit molecular characteristics of effector organs.
Confirmation of Encapsulated Nerve Structures in the Human Vocal Cord
Published in Acta Oto-Laryngologica, 1989
The overall morphology of the encapsulated nerve structure in the human vocal cord was studied. The nerve consists of a straight portion containing a striated muscle fiber and several side branches. The side branches consist of non-myelinated fibers and dense collagen bundles. Their ultrastructure resembles that of the Golgi tendon organ, suggestive of a pressure receptor. Since the side branches extend between muscle fibers of the vocal muscle, their purpose may be to detect the stiffness of the vocal cord. One end of the intracapsular muscle fiber terminates in the capsule and the other, tapered end terminates in dense collagen bundles within the capsular space. Contraction of muscle fiber alters the stiffness of the intracapsular space and may control the sensory threshhold of the nerve ending.
Biomechanical Properties of Fascial Tissues and Their Role as Pain Generators
Published in Journal of Musculoskeletal Pain, 2010
Robert Schleip, Adjo Zorn, Werner Klingler
Objectives: To highlight the load bearing functions of fascial tissues and their proneness to micro tearing during physiological or excessive loading, to review histological evidence for a proprioceptive as well as nociceptive innervation of fascia, and to emphasize the potential role of injury, inflammation, and/or neural sensitization of the posterior layer of the human lumbar fascia in non-specific low back pain. Findings: In addition to a tensional load bearing function of tendons and ligaments, muscles transmit a significant portion of their force via their epimysia to laterally positioned tissues, such as to synergistic or antagonistic muscles. Fascial tissues are commonly used as elastic springs [catapult action] during oscillatory movements, such as walking, hopping, or running, in which the supporting skeletal muscles contract rather isometrically. They are prone to viscoelastic deformations such as creep, hysteresis, and relaxation. Such temporary deformations alter fascial stiffness and may take several hours for recovery. There is a gradual transition zone between reversible viscoelastic deformation and complete tissue tearing. Micro tearing of collagenous fibers and their interconnections have been documented in this zone. Fascia is densely innervated by myelinated nerve endings which are assumed to serve a proprioceptive function. These are Pacini [and paciniform] corpuscles, Golgi tendon organs, and Ruffini endings. In addition they are innervated by free endings, containing substance P, suggestive of a nociceptive function. New findings suggest that noicipetive activity of epimysial fasciae play a major role in delayed onset muscle soreness subsequent to repetitive concentric exercise. Conclusions: Fascial tissues serve important load bearing functions. The innervation of fascia indicates a sensory role as an organ for propriocepton, and also a potential nociceptive function. Micro tearing and/or inflammation of fascia can be a direct source of musculoskeletal pain. Fascia may be an indirect source of back pain.
Related Knowledge Centers
- Central Nervous System
- Inner Ear
- Nerve Impulses
- Skeletal Muscle Fibers
- Neuroepithelial Bodies
- Taste Buds
- Sensory Receptor Cells