Morphometric studies on tenuissimus muscle spindles in the cat

1982 ◽  
Vol 171 (2) ◽  
pp. 137-150 ◽  
Author(s):  
Jan Kucera
Keyword(s):  
Muscle Spindles

Absence of Muscle Spindles in Human Facial Muscles

2004 ◽  
Vol 35 (03) ◽  
Author(s):  
PP Urban ◽  
J Bohl ◽  
L Abrao ◽  
E Stofft
Keyword(s):  
Muscle Spindles ◽  
Facial Muscles

scholarly journals The path from trigeminal asymmetry to cognitive impairment: a behavioral and molecular study

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Maria Paola Tramonti Fantozzi ◽  
Giulia Lazzarini ◽  
Vincenzo De Cicco ◽  
Angela Briganti ◽  
Serena Argento ◽  
...  
Keyword(s):  
Pupil Size ◽  
Muscle Spindles ◽  
Molecular Study ◽  
Contralateral Side ◽  
Acute Effects ◽  
Adult Rats ◽  
Afferent Inputs ◽  
Acute And Chronic Effects ◽  
The Brain ◽  
Mandibular Branch

AbstractTrigeminal input exerts acute and chronic effects on the brain, modulating cognitive functions. Here, new data from humans and animals suggest that these effects are caused by trigeminal influences on the Locus Coeruleus (LC). In humans subjects clenching with masseter asymmetric activity, occlusal correction improved cognition, alongside with reductions in pupil size and anisocoria, proxies of LC activity and asymmetry, respectively. Notably, reductions in pupil size at rest on the hypertonic side predicted cognitive improvements. In adult rats, a distal unilateral section of the trigeminal mandibular branch reduced, on the contralateral side, the expression of c-Fos (brainstem) and BDNF (brainstem, hippocampus, frontal cortex). This counterintuitive finding can be explained by the following model: teeth contact perception loss on the lesioned side results in an increased occlusal effort, which enhances afferent inputs from muscle spindles and posterior periodontal receptors, spared by the distal lesion. Such effort leads to a reduced engagement of the intact side, with a corresponding reduction in the afferent inputs to the LC and in c-Fos and BDNF gene expression. In conclusion, acute effects of malocclusion on performance seem mediated by the LC, which could also contribute to the chronic trophic dysfunction induced by loss of trigeminal input.

Computer Simulation of the Responses of Human Motoneurons to Composite 1A EPSPS: Effects of Background Firing Rate

1997 ◽  
Vol 77 (1) ◽  
pp. 405-420 ◽  
Author(s):  
Kelvin E. Jones ◽  
Parveen Bawa
Keyword(s):  
Computer Simulation ◽  
Firing Rate ◽  
Time Course ◽  
Current Model ◽  
Response Probability ◽  
Muscle Spindles ◽  
Excitatory Postsynaptic Potential ◽  
Biophysical Properties ◽  
Rhythmic Firing ◽  
The Relationship

Jones, Kelvin E. and Parveen Bawa. Computer simulation of the responses of human motoneurons to composite 1A EPSPS: effects of background firing rate. J. Neurophysiol. 77: 405–420, 1997. Two compartmental models of spinal alpha motoneurons were constructed to explore the relationship between background firing rate and response to an excitatory input. The results of these simulations were compared with previous results obtained from human motoneurons and discussed in relation to the current model for repetitively firing human motoneurons. The morphologies and cable parameters of the models were based on two type-identified cat motoneurons previously reported in the literature. Each model included five voltage-dependent channels that were modeled using Hodgkin-Huxley formalism. These included fast Na+ and K+ channels in the initial segment and fast Na+ and K+ channels as well as a slow K+ channel in the soma compartment. The density and rate factors for the slow K+ channel were varied until the models could reproduce single spike AHP parameters for type-identified motoneurons in the cat. Excitatory synaptic conductances were distributed along the equivalent dendrites with the same density described for la synapses from muscle spindles to type-identified cat motoneurons. Simultaneous activation of all synapses on the dendrite resulted in a large compound excitatory postsynaptic potential (EPSP). Brief depolarizing pulses injected into a compartment of the equivalent dendrite resulted in pulse potentials (PPs), which resembled the compound EPSPs. The effects of compound EPSPs and PPs on firing probability of the two motoneuron models were examined during rhythmic firing. Peristimulus time histograms, constructed between the stimulus and the spikes of the model motoneuron, showed excitatory peaks whose integrated time course approximated the time course of the underlying EPSP or PP as has been shown in cat motoneurons. The excitatory peaks were quantified in terms of response probability, and the relationship between background firing rate and response probability was explored. As in real human motoneurons, the models exhibited an inverse relationship between response probability and background firing rate. The biophysical properties responsible for the relationship between response probability and firing rate included the shapes of the membrane voltage trajectories between spikes and nonlinear changes in PP amplitude during the interspike interval at different firing rates. The results from these simulations suggest that the relationship between response probability and background firing rate is an intrinsic feature of motoneurons. The similarity of the results from the models, which were based on the properties of cat motoneurons, and those from human motoneurons suggests that the biophysical properties governing rhythmic firing in human motoneurons are similar to those of the cat.

On the regional distribution of muscle spindles

1989 ◽  
Vol 12 (4) ◽  
pp. 666-666
Author(s):  
John B. Munson ◽  
Robert C. Foehring
Keyword(s):  
Regional Distribution ◽  
Muscle Spindles

scholarly journals FINE STRUCTURE OF RAT INTRAFUSAL MUSCLE FIBERS

1971 ◽  
Vol 51 (1) ◽  
pp. 83-103 ◽  
Author(s):  
William K. Ovalle
Keyword(s):  
Muscle Fiber ◽  
Muscle Fibers ◽  
Muscle Spindles ◽  
Intrafusal Muscle ◽  
Dense Granules ◽  
Intrafusal Muscle Fibers ◽  
Sarcotubular System ◽  
Nuclear Chain ◽  
T System ◽  
Nuclear Bag

An ultrastructural comparison of the two types of intrafusal muscle fibers in muscle spindles of the rat was undertaken. Discrete myofibrils with abundant interfibrillar sarcoplasm and organelles characterize the nuclear chain muscle fiber, while a continuous myofibril-like bundle with sparse interfibrillar sarcoplasm distinguishes the nuclear bag muscle fiber. Nuclear chain fibers possess well-defined and typical M bands in the center of each sarcomere, while nuclear bag fibers contain ill-defined M bands composed of two parallel thin densities in the center of the pseudo-H zone of each sarcomere. Mitochondria of nuclear chain fibers are larger and more numerous than they are in nuclear bag fibers. Mitochondria of chain fibers, in addition, often contain conspicuous dense granules, and they are frequently intimately related to elements of the sarcoplasmic reticulum (SR). Striking differences are noted in the organization and degree of development of the sarcotubular system. Nuclear bag fibers contain a poorly developed SR and T system with only occasional junctional couplings (dyads and triads). Nuclear chain fibers, in contrast, possess an unusually well-developed SR and T system and a variety of multiple junctional couplings (dyads, triads, quatrads, pentads, septads). Greatly dilated SR cisternae are common features of nuclear chain fibers, often forming intimate associations with T tubules, mitochondria, and the sarcolemma. Such dilatations of the SR were not encountered in nuclear bag fibers. The functional significance of these structural findings is discussed.

The three-dimensional cytoarchitecture of developing murine muscle spindles

1981 ◽  
Vol 87 (1) ◽  
pp. 133-147 ◽  
Author(s):  
Kenneth Kozeka ◽  
Marcia Ontell
Keyword(s):  
Three Dimensional ◽  
Muscle Spindles
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