The role of muscle spindles in constraining motor control

2002 ◽  
Vol 44-46 ◽  
pp. 943-949 ◽  
Author(s):  
Bjørn Gilbert Nielsen
Keyword(s):  
Motor Control ◽  
Muscle Spindles

The Mammalian Muscle Spindle

Physiology ◽  
1997 ◽  
Vol 12 (1) ◽  
pp. 37-42 ◽  
Author(s):  
U Proske
Keyword(s):  
Motor Control ◽  
Muscle Spindle ◽  
Muscle Spindles ◽  
Mammalian Muscle ◽  
Intrafusal Fibers ◽  
Sensory Endings

A brief, summarizing description is given of the structure and physiology of the mammalian muscle spindle. The question is addressed, What might be the roles of the three different kinds of intrafusal fibers on which the sensory endings lie? The role of muscle spindles in proprioception and in motor control is discussed.

Units of Action in Motor Control: Role of Response Complexity and target Speed

1995 ◽  
Vol 8 (1) ◽  
pp. 27-49 ◽  
Author(s):  
Dana M. Schneider ◽  
Richard A. Schmidt
Keyword(s):  
Motor Control ◽  
Target Speed

The Role of Specific Motor Control Exercises

2020 ◽  
pp. 71-99
Author(s):  
Dianne E. Andreotti ◽  
Sean G. T. Gibbons ◽  
Francesco Cantarelli
Keyword(s):  
Motor Control

scholarly journals Gamma motor neurons survive and exacerbate alpha motor neuron degeneration in ALS

2016 ◽  
Vol 113 (51) ◽  
pp. E8316-E8325 ◽  
Author(s):  
Melanie Lalancette-Hebert ◽  
Aarti Sharma ◽  
Alexander K. Lyashchenko ◽  
Neil A. Shneider
Keyword(s):  
Motor Neuron ◽  
Mouse Models ◽  
Motor Neurons ◽  
Muscle Spindles ◽  
Excitatory Input ◽  
Synaptic Excitation ◽  
Fused In Sarcoma ◽  
Alpha Motor Neuron ◽  
Lateral Sclerosis

The molecular and cellular basis of selective motor neuron (MN) vulnerability in amyotrophic lateral sclerosis (ALS) is not known. In genetically distinct mouse models of familial ALS expressing mutant superoxide dismutase-1 (SOD1), TAR DNA-binding protein 43 (TDP-43), and fused in sarcoma (FUS), we demonstrate selective degeneration of alpha MNs (α-MNs) and complete sparing of gamma MNs (γ-MNs), which selectively innervate muscle spindles. Resistant γ-MNs are distinct from vulnerable α-MNs in that they lack synaptic contacts from primary afferent (IA) fibers. Elimination of these synapses protects α-MNs in the SOD1 mutant, implicating this excitatory input in MN degeneration. Moreover, reduced IAactivation by targeted reduction of γ-MNs in SOD1G93Amutants delays symptom onset and prolongs lifespan, demonstrating a pathogenic role of surviving γ-MNs in ALS. This study establishes the resistance of γ-MNs as a general feature of ALS mouse models and demonstrates that synaptic excitation of MNs within a complex circuit is an important determinant of relative vulnerability in ALS.

The Early Development of Muscle Spindles in the Rat

1973 ◽  
Vol 12 (1) ◽  
pp. 175-195
Author(s):  
ALICE MILBURN
Keyword(s):  
Close Association ◽  
Large Diameter ◽  
Muscle Spindles ◽  
Muscle Fibres ◽  
Intrafusal Muscle ◽  
Intrafusal Fibres ◽  
Fusimotor Innervation ◽  
Nuclear Chain ◽  
Intramuscular Nerve

The morphogenesis of muscle spindles in rat lower hind-limb muscles has been investigated using the electron microscope. The earliest detectable spindles are seen in the 19.5-day foetus and consist of a single myotube bearing simple nerve terminals of the large primary afferent axon from nearby unmyelinated intramuscular nerve trunks. The capsule forms by an extension of the perineural epithelium of the supplying nerve fasciculus, and is confined initially to the innervated zone. Myonuclei accumulate in this region, so that the first intrafusal muscle fibre to develop is a nuclear-bag fibre. Myoblasts, present within the capsule of the spindle throughout its development, fuse to form a smaller less-differentiated myotube by the 20-day foetal stage. This new myotube matures by close association with the initial fibre, and by birth (21-22 days gestation) has formed the smaller, intermediate bag fibre, that has been identified histochemically and ultrastructurally in the adult. The nuclear-chain fibres develop in the same way; myoblasts fuse to form satellite myotubes that mature in pseudopodial apposition to one of the other fibres within its basement membrane. This apposition consists of extensions of sarcoplasm from the developing myotube into the supporting fibre. By the 4-day postnatal stage the full adult complement of 4 intrafusal muscle fibres is present, although ultrastructural variations, seen in the adult, are not differentiated. The fusimotor innervation begins to arrive at birth, but is not mature until the 12th postnatal day, when the myofibrillar ultrastructural differentiation, including the loss of the M-line in the large-diameter bag fibre, is complete. The periaxial space appears at the same time. It is suggested that the sequential development of the intrafusal fibres is a reflexion of the decreasing morphogenetic effect of the afferent innervation, whereas the role of the fusimotor innervation is in ultrastructural, myofibrillar differentiation.

Steady-state response of quadriplegic subjects to inspiratory resistive load

1986 ◽  
Vol 60 (5) ◽  
pp. 1482-1492 ◽  
Author(s):  
V. Im Hof ◽  
H. Dubo ◽  
V. Daniels ◽  
M. Younes
Keyword(s):  
Steady State ◽  
Chest Wall ◽  
Muscle Spindles ◽  
Normal Subjects ◽  
Afferent Feedback ◽  
Resistive Load ◽  
State Response ◽  
The Face ◽  
Inspiratory Resistance

Normal subjects preserve tidal volume (VT) in the face of added inspiratory resistance by increasing maximal amplitude and duration of the rising phase of respiratory driving pressure (DP) and by changing the shape of this phase to one that is more concave to the time axis. To explore the possible role of chest wall afferents in mediating these responses, we determined averaged DP in eight quadriplegic subjects during steady-state unloaded breathing and while breathing through an inspiratory resistance (8.5 cmH2O X 1(-1) X s). As with normal subjects, quadriplegics preserved VT (loaded VT = 106% control) by utilizing all three mechanisms. However, prolongation of the inspiratory duration derived from the DP waveform (+22% vs. +42%) and shape response were significantly less in the quadriplegic subjects. Shape response was completely absent in subjects with C4 lesions. The results provide strong evidence that respiratory muscle spindles are responsible for shape response and that changes in afferent feedback from the chest wall play an important role in mediating inspiratory prolongation.

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