Spinal reflexes as a basis for tremor in the premammillary cat

1978 ◽  
Vol 56 (3) ◽  
pp. 375-383 ◽  
Author(s):  
T. R. Nichols ◽  
R. B. Stein ◽  
P. Bawa

A maintained tremor observed in premammillary cats has been studied by varying the load attached to the soleus muscle, by electrical recording, and stimulation. The frequency and amplitude of the tremor varies widely with changes in elastic or inertial loading (springs or flywheels). These variations agree well with predictions based on the idea that the tremor is maintained by reflexes reinforcing a tendency for oscillation in a mass-spring system (which includes the elasticity of the muscle). Spinal stretch reflexes are probably responsible since a relatively fixed delay of 8.5 ± 2.9 ms is observed between the peaks of recorded afferent and electromyographic activity. Stimulation of the lateral gastrocnemius – soleus nerve completely resets the tremor, again suggesting a reflex origin.

1994 ◽  
Vol 186 (1) ◽  
pp. 75-93
Author(s):  
A. C. Guimaraes ◽  
W. Herzog ◽  
M. Hulliger ◽  
Y. T. Zhang ◽  
S. Day

Distributed stimulation of ventral root (VR) filaments and pseudo-random interpulse intervals (based on a Gaussian distribution with a coefficient of variation of 12.5%) were used to modulate electromyographic activity (EMG) and force of the cat soleus muscle to assess the EMG-force relationship. A protocol consisting of addition and rate modulation of ten VR filaments that contain alpha motoneurones to the soleus muscle was adopted. EMG was measured using indwelling electrodes and forces were measured at the distal tendon using a strain transducer. EMG records obtained using this approach were similar in the time and frequency domains to those obtained during voluntary contractions. Force records obtained from stimulation of single VR filaments showed summation effects typical of irregular interpulse intervals. The overall relationship between integrated rectified EMG (IEMG) and mean force was found to be non-linear. At low and high stimulation levels, IEMG tended to increase proportionally more than mean force. In the intermediate stimulation region (i.e. producing forces between approximately 5% and 88% of the maximal tetanic force), the IEMG-mean force relationship was virtually linear. Muscles with a homogeneous fibre type composition, such as the cat soleus muscle, have been reported to have a linear EMG-force relationship.


2000 ◽  
Vol 83 (4) ◽  
pp. 2063-2070 ◽  
Author(s):  
Yoshiyuki Takada ◽  
Takao Miyahara ◽  
Tatsuya Tanaka ◽  
Takashi Ohyama ◽  
Yoshio Nakamura

A previous study has demonstrated that the soleus H reflex is facilitated in association with voluntary teeth clenching in proportion with biting force in humans. The present study tried to elucidate the functional significance of this facilitation of the soleus H reflex, by examining 1) whether the facilitation of the H reflex is reciprocal or nonreciprocal between the ankle extensors and flexors and 2) whether the reciprocal Ia inhibition of crural muscles is facilitated or depressed in association with voluntary teeth clenching. The H reflex of the pretibial muscles was evoked by stimulation of the common peroneal nerve in seven healthy subjects with no oral dysfunction. The pretibial H reflex was facilitated in association with voluntary teeth clenching in a force-dependent manner. The facilitation started preceding the onset of electromyographic activity of the masseter muscle. Stimulation of the common peroneal nerve at low intensities subthreshold for evoking the M wave of the pretibial muscles inhibited the soleus H reflex after a short latency corresponding with a disynaptic inhibition, indicating that the reciprocal Ia inhibition was depressed in association with voluntary teeth clenching. Thus, the present study has shown that voluntary teeth clenching evokes a nonreciprocal facilitation of ankle extensor and flexor muscles and attenuated reciprocal Ia inhibition from the pretibial muscles to the soleus muscle. It is concluded that voluntary teeth clenching contributes to improve stability of stance rather than smoothness of movements.


1964 ◽  
Vol 207 (2) ◽  
pp. 303-307 ◽  
Author(s):  
B. J. Prout ◽  
J. H. Coote ◽  
C. B. B. Downman

In cats anesthetized with chloralose-urethane mixture, stimulation of an afferent nerve evoked a vasoconstrictor reflex (VCR) and a galvanic skin response (GSR) in the pads of the feet. Stimulation of the ventromedial medullary reticular substance at the level of the obex abolished the VCR and the GSR. VCR could also be reduced by occlusion during prolonged stimulation of another spinal or visceral afferent pathway. Medulla stimulation was effective without itself causing a sympathetic discharge to the paw, showing that inhibition rather than occlusion was operative. Anterior cerebellar stimulation also inhibited the VCR. Carotid sinus nerve stimulation did not abolish the VCR. It is concluded that the effective mechanism includes a bulbospinal inhibitory path projecting on a spinal vasoconstrictor reflex arc. This arrangement is similar to the descending pathways inhibiting other spinal reflexes but the VCR-inhibitory path can be activated independently of them.


NANO ◽  
2015 ◽  
Vol 10 (02) ◽  
pp. 1550024 ◽  
Author(s):  
S. Kamal Jalali ◽  
M. Hassan Naei ◽  
Nicola Maria Pugno

Application of single layered graphene sheets (SLGSs) as resonant sensors in detection of ultra-fine nanoparticles (NPs) is investigated via molecular dynamics (MD) and nonlocal elasticity approaches. To take into consideration the effect of geometric nonlinearity, nonlocality and atomic interactions between SLGSs and NPs, a nonlinear nonlocal plate model carrying an attached mass-spring system is introduced and a combination of pseudo-spectral (PS) and integral quadrature (IQ) methods is proposed to numerically determine the frequency shifts caused by the attached metal NPs. In MD simulations, interactions between carbon–carbon, metal–metal and metal–carbon atoms are described by adaptive intermolecular reactive empirical bond order (AIREBO) potential, embedded atom method (EAM), and Lennard–Jones (L–J) potential, respectively. Nonlocal small-scale parameter is calibrated by matching frequency shifts obtained by nonlocal and MD simulation approaches with same vibration amplitude. The influence of nonlinearity, nonlocality and distribution of attached NPs on frequency shifts and sensitivity of the SLGS sensors are discussed in detail.


2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Venkata K. Yadalam ◽  
B. F. Feeny

A method of modal analysis by a mass-weighted proper orthogonal decomposition for multi-degree-of-freedom and distributed-parameter systems of arbitrary mass distribution is outlined. The method involves reduced-order modeling of the system mass distribution so that the discretized mass matrix dimension matches the number of sensed quantities, and hence the dimension of the response ensemble and correlation matrix. In this case, the linear interpolation of unsensed displacements is used to reduce the size of the mass matrix. The idea is applied to the modal identification of a mass-spring system and an exponential rod.


1977 ◽  
Vol 40 (1) ◽  
pp. 95-105 ◽  
Author(s):  
R. Capek ◽  
B. Esplin

1. The transmission in the spinal monosynaptic pathway was studied during repetitive stimulation of a motor nerve by 10 stimuli at 2, 5, or 10 Hz in spinal cats. Initially, the amplitudes of the monosynaptic responses rapidly declined, reaching a plateau after a few stimuli. The level of the plateau was inversely related to the frequency of stimulation. 2. This depression of monosynaptic response was seen only when the same pathway was stimulated; the response elicited from the lateral gastrocnemius was not depressed when preceded by stimulation of the medial gastrocnemius nerve and vice versa. Pretreatment with semicarbazide left the homosynaptic depression unchanged while suppressing the dorsal root reflex. The participation of a depolarization of primary afferents in the described depression is, therefore, unlikely. 3. The decrease of transmitter release by successive volleys, which is the cause of the observed depression, could conceivably be related to the depletion of transmitter stores. 4. A procedure is described, based on this assumption, which allows the calculation of transmitter turnover. The input-output relation in the spinal monosynaptic pathway is used to convert the amplitudes of monosynaptic responses to the amounts of transmitter, both relative to the maximum response. The changes of transmitter release are analyzed under the assumption that each volley releases instantaneously a constant fraction of the transmitter store available for release and that this store is replenished at a constant fraction of the depleted part per second. 5. The values of fractional release per volley were about 0.4, irrespective of frequency of stimulation. 6. The values of fractional replenishment per second ranged from about 1 to 5 on the average, depending directly on the frequency of stimulation. 7. It is suggested that the described procedure might be useful in analyzing drug effects on synaptic transmission.


1985 ◽  
Vol 54 (6) ◽  
pp. 1383-1395 ◽  
Author(s):  
J. E. Gregory ◽  
D. L. Morgan ◽  
U. Proske

A continuing controversy surrounds the question of whether Golgi tendon organs are examples of receptors in which impulses may be generated at more than one site. This paper reports a systematic examination of a number of models incorporating single or multiple impulse generators and of the compatibility of their predictions with experimental observations. Two phenomena, in particular, that must be accounted for are nonlinear summation and cross-adaptation. When two motor units each with a direct effect on the tendon organ are stimulated together, the rate of discharge is greater than either individual rate but is less than their sum. In cross-adaptation a conditioning response elicited by one motor unit contraction produces adaptation of the discharge associated with stimulation of a second motor unit. A model with a central impulse generator can be modified to account for nonlinear summation by postulating a nonlinear transformation in the generator current-to-impulse rate conversion. Experiments measuring summation of responses to stimulation of three inputs produced results that did not support this model. Another variation of the model, which had a nonlinearity in the tension-to-current step and cross-connections (mechanical or neural) between tendon strands stressed by contracting muscle fibers, was able to account for the observations. A second model that provided the right predictions was a multiple impulse generator with cross-connections. Which of the two models best fits the experimental observations can be decided by comparing the calculated summation coefficients and cross-adaptation coefficients. A central impulse generator predicts a negative correlation, the multiple impulse generator a positive correlation. All of the observations were made using tendon organs of cat soleus muscle. Responses were recorded to stimulation of filaments of ventral root. In a comparison between 20 pairs of responses from six tendon organs the correlation between summation and cross-adaptation coefficients was found to be significantly positive. We conclude that the tendon organ model that accurately predicts all of the experimental observations incorporates multiple generators.


2013 ◽  
Vol 14 (5) ◽  
pp. 1228-1251 ◽  
Author(s):  
Yan Li ◽  
I-Liang Chern ◽  
Joung-Dong Kim ◽  
Xiaolin Li

AbstractWe use front tracking data structures and functions to model the dynamic evolution of fabric surface. We represent the fabric surface by a triangulated mesh with preset equilibrium side length. The stretching and wrinkling of the surface are modeled by the mass-spring system. The external driving force is added to the fabric motion through the “Impulse method” which computes the velocity of the point mass by superposition of momentum. The mass-spring system is a nonlinear ODE system. Added by the numerical and computational analysis, we show that the spring system has an upper bound of the eigen frequency. We analyzed the system by considering two spring models and we proved in one case that all eigenvalues are imaginary and there exists an upper bound for the eigen-frequency This upper bound plays an important role in determining the numerical stability and accuracy of the ODE system. Based on this analysis, we analyzed the numerical accuracy and stability of the nonlinear spring mass system for fabric surface and its tangential and normal motion. We used the fourth order Runge-Kutta method to solve the ODE system and showed that the time step is linearly dependent on the mesh size for the system.


1990 ◽  
Vol 63 (3) ◽  
pp. 395-403 ◽  
Author(s):  
T. M. Hamm

1. Recurrent inhibitory postsynaptic potentials (IPSPs) to and from motoneurons innervating the flexor digitorum longus (FDL) and flexor hallucis longus (FHL) muscles of the cat were investigated to determine whether recurrent inhibitory projections involving these motoneurons are similar--as would be consistent with the Ia and anatomic synergism of FDL and FHL--or are dissimilar, as are the activities of these muscles during locomotion (O'Donovan et al. 1982). 2. Composite recurrent IPSPs were recorded in several species of motoneurons innervating hindlimb muscles in response to stimulation of a number of muscle nerves in cats allowed to become unanesthetized after ischemic decapitation. 3. No recurrent IPSPs from stimulation of the FDL nerve were observed in motoneurons innervating FDL, FHL, lateral gastrocnemius-soleus (LG-S), medial gastrocnemius (MG), plantaris (Pl), tibialis anterior (TA), or extensor digitorum longus (EDL). 4. The recurrent IPSPs produced by stimulation of FHL were larger and found more frequently in LG-S than in FDL motoneurons. Recurrent inhibition from FHL was also greater in Pl than in FDL motoneurons. 5. The recurrent IPSPs produced by stimulation of LG-S, PL, and MG were larger in FHL than in FDL motoneurons, and those from LG-S and MG were found more frequently in FHL than in FDL motoneurons. 6. Stimulation of the TA nerve produces recurrent IPSPs in FDL but not in FHL motoneurons. A few FDL and FHL cells (6 of 23 and 9 of 34, respectively) received small (less than 0.5 mV) recurrent IPSPs from stimulation of the EDL nerve.(ABSTRACT TRUNCATED AT 250 WORDS)


2018 ◽  
Vol 7 (3) ◽  
pp. 31
Author(s):  
Rosa Virginia Hernández ◽  
Luis Fernando Mariño ◽  
Mawency Vergel

En este artículo se presenta la caracterización del conocimiento semántico evidenciado por un grupo de estudiantes en la representación externa a problemas de ecuaciones diferenciales lineales de segundo orden como modelos matemáticos. El trabajo fue cuantitativo de tipo exploratorio y descriptivo utilizando un cuestionario en la recolección de información. El soporte teórico que dio sentido al estudio fue el modelo de dos etapas propuesto por Mayer R. para la resolución de problemas matemáticos, el ciclo de modelación bajo la perspectiva cognitiva según Borromeo Ferri y la teoría de las representaciones de Goldin y Kaput. La investigación se centró específicamente en la fase de representación del modelo. Entre los principales hallazgos se destaca que cada participante hace su propia representación externa a conceptos como: sistema masa-resorte, peso, masa, punto de equilibrio, constante de elasticidad, punto de equilibrio, ley de Hooke, fuerza amortiguadora, fuerza externa, ley de Newton, entre otros. Se evidencian también dificultades en el tránsito del lenguaje natural al lenguaje matemático y la representación externa de cada una de los signos, símbolos o expresiones matemáticas inmersas en el problema de palabra, debido a que el resolutor tiene que construir un modelo mental de la situación real y plasmarlo en un modelo matemático. Lo anterior pone de manifiesto la importancia que tiene el conocimiento semántico en la etapa de traducción cuando se intentan resolver problemas como situaciones reales a modelar.Palabras clave: resolución de problemas, ciclos de modelación, problemas de palabra, representaciones externas, conocimiento extra matemático, modelación matemática. AbstractThis article presents the characterization of the semantic knowledge evidenced by a group of students in the external representation to problems of second order linear differential equations as mathematical models. The work was quantitative exploratory and descriptive using a questionnaire in the collection of information. The theoretical support that gave meaning to the study was the two-stage model proposed by Mayer R. for solving mathematical problems, the modeling cycle under the cognitive perspective according to Borromeo Ferri and the theory of representations of Goldin and Kaput. The research focused specifically on the representation phase of the model. Among the main findings is that each participant makes his own external representation to concepts such as: mass-spring system, weight, mass, equilibrium point, constant of elasticity, equilibrium point, Hooke's law, damping force, external force, law of Newton, among others. Difficulties are also evident in the transition from natural language to mathematical language and the external representation of each of the signs, symbols or mathematical expressions involved in the word problem, because the resolver has to construct a mental model of the real situation and translate it into a mathematical model. This demonstrates the importance of semantic knowledge in the translation stage when trying to solve problems as real situations to be modeledKeywords: problem solving, modeling cycles, word problems, external representations, extra mathematical knowledge, mathematical modeling.ResumoEste artigo apresenta a caracterização do conhecimento semântico evidenciado por um grupo de estudantes na representação externa a problemas de equações diferenciais lineares de segunda ordem como modelos matemáticos. O trabalho foi quantitativo exploratório e descritivo usando um questionário na coleta de informações. O suporte teórico que deu sentido ao estudo foi o modelo de dois estágios proposto por Mayer R. para resolver problemas matemáticos, o ciclo de modelagem sob a perspectiva cognitiva de acordo com Borromeo Ferri e a teoria das representações de Goldin e Kaput. A pesquisa focalizou especificamente a fase de representação do modelo. Entre os principais achados, cada participante faz sua própria representação externa para conceitos como: sistema de massa-mola, peso, massa, ponto de equilíbrio, constante de elasticidade, ponto de equilíbrio, lei de Hooke, força de amortecimento, força externa, lei de Newton, entre outros. As dificuldades também são evidentes na transição da linguagem natural para a linguagem matemática e a representação externa de cada um dos signos, símbolos ou expressões matemáticas envolvidas na palavra problema, porque o resolvedor tem que construir um modelo mental da situação real e traduzi-lo para um modelo matemático. Isso demonstra a importância do conhecimento semântico na fase de tradução ao tentar resolver problemas como situações reais a serem modeladas. ______________________________________________________ Palavras-chave: resolução de problemas, ciclos de modelagem, problemas de palavra, representação externa, conhecimento extra matemático, modelagem matemática


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