The spike trains of afferent fibers innervating muscle spindles and Golgi tendon organs in the me... more The spike trains of afferent fibers innervating muscle spindles and Golgi tendon organs in the medial gastrocnemius muscle were recorded during spontaneous contractions in either decerebrate cats or decapitate cats treated with L-dopa. For each afferent fiber, the approximate location of its receptor within the muscle was determined. Cross-correlation histograms were compiled from the simultaneously recorded spike trains of pairs of afferent fibers (Ia, Ib, spindle II) to determine if the degree of temporal correlation in their discharge was related to the mutual proximity of the receptors they innervated within the muscle. The frequency of occurrence and degree of correlated activity between pairs of muscle afferents, regardless of receptor type, was much greater in the decerebrate preparations than in the decapitate-L-dopa preparations. However, in all cases, the extent of correlated activity appeared to be unrelated to the relative locations of the receptors. The results suggest ...
The spike-triggered averaging technique (26) was used to determine whether the synaptic input fro... more The spike-triggered averaging technique (26) was used to determine whether the synaptic input from medial gastrocnemius (MG) Ia-afferent fibers to homonymous motoneurons is "topographically weighted" (22) by means of differences in projection frequency, excitatory postsynaptic potential (EPSP) amplitude, or a combination of both factors. Motoneurons were classified as either "same branch" or "other branch," depending on whether a Ia-afferent fiber and motor axon were contained in the same or different intramuscular nerve branches. No difference was found in the projection frequency of Ia-afferents to the same branch and other branch motoneurons (95 versus 94%, respectively). The mean EPSP amplitude was larger in the same branch group of motoneurons (92 +/- 8 (SE) microV; n = V; n = 97) than in the other branch group (77 +/- 7 microV; n = 79). This difference was most striking in high-rheobase (greater than or equal to 10 nA) motoneurons, for which the m...
1. Steady-state recurrent (Renshaw) inhibitory postsynaptic potentials (RIPSPs) were evoked in ca... more 1. Steady-state recurrent (Renshaw) inhibitory postsynaptic potentials (RIPSPs) were evoked in cat triceps surae motoneurons by stimulating the heteronymous muscle nerve at 100 Hz after dorsal root section. The effective synaptic currents (i.e., the net synaptic current measured at the soma, IN) underlying these inhibitory potentials were measured with a modified voltage-clamp technique. 2. The average value of the effective synaptic currents measured in medial gastrocnemius (MG) motoneurons was 0.4 nA. There was no significant correlation between the IN measured in individual cells and motoneuron input resistance (RN), rheobase (IR), duration of the spike afterhyperpolarization (AHPt1/2), or putative motor-unit type, although the steady-state inhibitory post-synaptic potential (IPSP) amplitudes were correlated with all of these parameters. 3. Steady-state recurrent inhibition was accompanied by a small (3.5%, on average) decrease in the resting input resistance of the motoneurons. ...
1. We have developed a technique to measure the total amount of current from a synaptic input sys... more 1. We have developed a technique to measure the total amount of current from a synaptic input system that reaches the soma of a motoneuron under steady-state conditions. We refer to this quantity as the effective synaptic current (IN) because only that fraction of the synaptic current that actually reaches the soma and initial segment of the cell affects its recruitment threshold and firing frequency. 2. The advantage of this technique for analysis of synaptic inputs in comparison to the standard measurements of synaptic potentials is apparent from Ohm's law. Steady-state synaptic potentials recorded at the soma of a cell are the product of IN and input resistance (RN), which is determined by intrinsic cellular properties such as cell size and membrane resistivity. Measuring IN avoids the confounding effect of RN on the amplitudes of synaptic potentials and thus provides a more direct assessment of the magnitude of a synaptic input. 3. Steady-state synaptic inputs were generated...
The responses of Golgi tendon organs to single motor unit contractions were studied to determine ... more The responses of Golgi tendon organs to single motor unit contractions were studied to determine whether receptors located in the same muscle region respond to a common set of motor units. In each of five experiments we isolated a large fraction (25‐65%) of the motor units of the cat tibialis posterior muscle and determined to which of the units each of several tendon organs was responsive. Each tendon organ was excited by from two to fifteen of the isolated motor units, including units which produced very small forces. However, there was a much greater probability for large force units to excite a given receptor than for small force units to do so. The number of motor units which produced either an 'unloading' or an 'off response' exceeded, on average, the number of motor units which excited the same tendon organ. The extent to which single motor units excited both of a pair of tendon organs was examined statistically in relation to the mutual proximity of the recep...
It has recently been proposed that the recruitment of motoneurons is correlated with their type r... more It has recently been proposed that the recruitment of motoneurons is correlated with their type rather than their size. To test this hypothesis the axonal conduction velocities (CVs) of 92 pairs of soleus motoneurons (all of the same histochemical type) were compared with their recruitment order. By means of spike-triggered averaging it has been shown that in 89 out of 92 pairs of soleus units the motoneuron with the lower CV was recruited first. The results indicate that orderly recruitment occurs in the absence of different types of motoneurons and is correlated with cell size within a cell type.
SummaryThe model of tendon organ activation proposed by Houk and Henneman (1967) has been tested ... more SummaryThe model of tendon organ activation proposed by Houk and Henneman (1967) has been tested by considering two of its implicit predictions: (1) that only a select group of motor units within a muscle can provide an adequate stimulus to a given tendon organ; and (2) that due to the presence of motor units that can “unload” a given tendon organ, its response to whole muscle contraction can be less vigorous than that to contraction of just the excitatory motor units alone. Tendon organ afferents from the soleus muscle of the cat were functionally isolated from dorsal root filaments. The L7 and S1 ventral roots were split into 25 to 50 “natural” subdivisions, each of which was stimulated at 50 to 100 Hz for 1.5 s. The subdivided filaments were segregated into two groups; those which when stimulated elicited discharge from the Ib afferent (“excitatory” filaments) and those which did not (“non-excitatory” filaments). In ten of eleven experiments, it was found that when all the excitatory filaments were separated out, concurrent stimulation of all the non-excitatory filaments failed to excite the tendon organ, even when these filaments generated over 90% of the muscle's peak tetanic tension. The response of a tendon organ to stimulation of just its excitatory filaments often exceeded its response to whole muscle stimulation. However, several exceptions to this finding were observed, indicating that some tendon organs are affected by “off-line” forces. In general, the present results lend strong support to the Houk and Henneman model.
... the late Nicolai Bernstein, Israel Gelfand and Michael Tsetlin; Bernstein's student,... more ... the late Nicolai Bernstein, Israel Gelfand and Michael Tsetlin; Bernstein's student, Victor Gurfinkel; Ludmila Kudina and Raisa Person; Yuri Arshavsky, Michael Berkinblit, Tatiana Deliagina, Anatole Feldman, Olga Fookson, Sergei Kashin, Yakov Kots, Andrey Kulagin, Mark ...
Determinism is the metaphysical doctrine that the whole of world history is uniquely fixed by law... more Determinism is the metaphysical doctrine that the whole of world history is uniquely fixed by laws of nature and initial conditions. In science, “deterministic ” is an epithet of theories or of laws that describe the temporal behavior of physical systems as strictly regular. Description of the Theory What is Determinism? To a first approximation, determinism is the claim “that there is at any instant exactly one physically possible future ” ([1] p 3). As such, determinism is a metaphysical doctrine about the course of the world as a whole, rather than a scientific theory. The French mathematician P. S. Laplace famously and vividly formulated metaphysical determinism in the early nineteenth century: “An intelligence that, at a given instant, could comprehend all the forces by which nature is animated and the respective situation of the beings that make it up, if moreover it were vast enough to submit these data to analysis, would encompass in the same formula the movements of the gre...
Tienda online donde Comprar Encyclopedia of Neuroscience al precio 1994,00 € de Binder, Marc D. |... more Tienda online donde Comprar Encyclopedia of Neuroscience al precio 1994,00 € de Binder, Marc D. | Hirokawa, Nobutaka | Windhorst, Uwe, tienda de Libros de Medicina, Libros de Neurologia - Neurologia general
The ionic molecules nitrate (NO 3 À) and nitrate (NO 2 À) were believed to be detrimental to huma... more The ionic molecules nitrate (NO 3 À) and nitrate (NO 2 À) were believed to be detrimental to human health, but recently are considered to be beneficial on the nitric oxide regulation in human body. The transporter protein, Nark, efficiently moves the NO 3 À and NO 2 À across the membrane to maintain the homeostatic level of the two ionic molecules as vital metabolites. Based on experimental evidence, Zheng and coworkers proposed a NO 3 À /NO 2 À exchange mechanism through the Nark. Here, we perform molecular dynamics simulations to probe the protein conformational changes associated with the NO 3 À /NO 2 À exchange cycle. Umbrella sampling is utilized to investigate the free energy profiles of NO 3 À and NO 2 À migrations.
The results of this study and its precedents suggest that the tetrapartite classification scheme ... more The results of this study and its precedents suggest that the tetrapartite classification scheme might have universal applicability to at least the muscle units of cat hindlimb muscles and perhaps any mammalian muscle in which fiber typing reveals the presence of FG, FI, FOG, and type SO fibers. A possible exception to this generalization involves a small (n = 18) but thoroughly examined sample of muscle units from the first deep lumbrical muscle of the cat's foot, which led Kernell et al. (30) to conclude that the FF, FR, and S classification scheme was not directly applicable to that muscle. However, histochemical fiber typing is not yet available for that muscle. Furthermore, more extensive sampling, use of a different stimulation regime in the fatigue test, and a more detailed analysis of the sag property might well reveal that the tetrapartite classification scheme is indeed appropriate for units of cat foot muscles.
Cross-correlation techniques have been used to study the responses of muscle spindle afferents fr... more Cross-correlation techniques have been used to study the responses of muscle spindle afferents from the soleus muscle of the cat to twitch contractions of single motor units. 2. Cross-correlograms (post-stimulus time histograms) were used to give the frequency of occurrence of a receptor spike at various times following the initiation of a motor unit contraction together with a display of the average twitch tension wave form. 3. The cross-correlograms revealed that the contraction of a single motor unit can be an effective stimulus to a spindle receptor and may induce afferent firing pattern alterations similar to those observed with whole muscle contraction. 4. The cross-correlograms also revealed quantitative differences in the response of a receptor to contraction of different motor units and to contraction of the same motor unit at different lengths. These differences reflect subtle changes in receptor deformation developed by the twitch of a motor unit under different conditions and by the twitches of different motor units. The results are consistent with anatomical data on the number and distribution of motor units and receptor organs in cat soleus. 5. These findings emphasize that rather than simply acting as generalized force or length sensors for the muscle as a whole, each receptor's spike train carries information about the state of a particular set of motor units.
The spike trains of afferent fibers innervating muscle spindles and Golgi tendon organs in the me... more The spike trains of afferent fibers innervating muscle spindles and Golgi tendon organs in the medial gastrocnemius muscle were recorded during spontaneous contractions in either decerebrate cats or decapitate cats treated with L-dopa. For each afferent fiber, the approximate location of its receptor within the muscle was determined. Cross-correlation histograms were compiled from the simultaneously recorded spike trains of pairs of afferent fibers (Ia, Ib, spindle II) to determine if the degree of temporal correlation in their discharge was related to the mutual proximity of the receptors they innervated within the muscle. The frequency of occurrence and degree of correlated activity between pairs of muscle afferents, regardless of receptor type, was much greater in the decerebrate preparations than in the decapitate-L-dopa preparations. However, in all cases, the extent of correlated activity appeared to be unrelated to the relative locations of the receptors. The results suggest ...
The spike-triggered averaging technique (26) was used to determine whether the synaptic input fro... more The spike-triggered averaging technique (26) was used to determine whether the synaptic input from medial gastrocnemius (MG) Ia-afferent fibers to homonymous motoneurons is "topographically weighted" (22) by means of differences in projection frequency, excitatory postsynaptic potential (EPSP) amplitude, or a combination of both factors. Motoneurons were classified as either "same branch" or "other branch," depending on whether a Ia-afferent fiber and motor axon were contained in the same or different intramuscular nerve branches. No difference was found in the projection frequency of Ia-afferents to the same branch and other branch motoneurons (95 versus 94%, respectively). The mean EPSP amplitude was larger in the same branch group of motoneurons (92 +/- 8 (SE) microV; n = V; n = 97) than in the other branch group (77 +/- 7 microV; n = 79). This difference was most striking in high-rheobase (greater than or equal to 10 nA) motoneurons, for which the m...
1. Steady-state recurrent (Renshaw) inhibitory postsynaptic potentials (RIPSPs) were evoked in ca... more 1. Steady-state recurrent (Renshaw) inhibitory postsynaptic potentials (RIPSPs) were evoked in cat triceps surae motoneurons by stimulating the heteronymous muscle nerve at 100 Hz after dorsal root section. The effective synaptic currents (i.e., the net synaptic current measured at the soma, IN) underlying these inhibitory potentials were measured with a modified voltage-clamp technique. 2. The average value of the effective synaptic currents measured in medial gastrocnemius (MG) motoneurons was 0.4 nA. There was no significant correlation between the IN measured in individual cells and motoneuron input resistance (RN), rheobase (IR), duration of the spike afterhyperpolarization (AHPt1/2), or putative motor-unit type, although the steady-state inhibitory post-synaptic potential (IPSP) amplitudes were correlated with all of these parameters. 3. Steady-state recurrent inhibition was accompanied by a small (3.5%, on average) decrease in the resting input resistance of the motoneurons. ...
1. We have developed a technique to measure the total amount of current from a synaptic input sys... more 1. We have developed a technique to measure the total amount of current from a synaptic input system that reaches the soma of a motoneuron under steady-state conditions. We refer to this quantity as the effective synaptic current (IN) because only that fraction of the synaptic current that actually reaches the soma and initial segment of the cell affects its recruitment threshold and firing frequency. 2. The advantage of this technique for analysis of synaptic inputs in comparison to the standard measurements of synaptic potentials is apparent from Ohm's law. Steady-state synaptic potentials recorded at the soma of a cell are the product of IN and input resistance (RN), which is determined by intrinsic cellular properties such as cell size and membrane resistivity. Measuring IN avoids the confounding effect of RN on the amplitudes of synaptic potentials and thus provides a more direct assessment of the magnitude of a synaptic input. 3. Steady-state synaptic inputs were generated...
The responses of Golgi tendon organs to single motor unit contractions were studied to determine ... more The responses of Golgi tendon organs to single motor unit contractions were studied to determine whether receptors located in the same muscle region respond to a common set of motor units. In each of five experiments we isolated a large fraction (25‐65%) of the motor units of the cat tibialis posterior muscle and determined to which of the units each of several tendon organs was responsive. Each tendon organ was excited by from two to fifteen of the isolated motor units, including units which produced very small forces. However, there was a much greater probability for large force units to excite a given receptor than for small force units to do so. The number of motor units which produced either an 'unloading' or an 'off response' exceeded, on average, the number of motor units which excited the same tendon organ. The extent to which single motor units excited both of a pair of tendon organs was examined statistically in relation to the mutual proximity of the recep...
It has recently been proposed that the recruitment of motoneurons is correlated with their type r... more It has recently been proposed that the recruitment of motoneurons is correlated with their type rather than their size. To test this hypothesis the axonal conduction velocities (CVs) of 92 pairs of soleus motoneurons (all of the same histochemical type) were compared with their recruitment order. By means of spike-triggered averaging it has been shown that in 89 out of 92 pairs of soleus units the motoneuron with the lower CV was recruited first. The results indicate that orderly recruitment occurs in the absence of different types of motoneurons and is correlated with cell size within a cell type.
SummaryThe model of tendon organ activation proposed by Houk and Henneman (1967) has been tested ... more SummaryThe model of tendon organ activation proposed by Houk and Henneman (1967) has been tested by considering two of its implicit predictions: (1) that only a select group of motor units within a muscle can provide an adequate stimulus to a given tendon organ; and (2) that due to the presence of motor units that can “unload” a given tendon organ, its response to whole muscle contraction can be less vigorous than that to contraction of just the excitatory motor units alone. Tendon organ afferents from the soleus muscle of the cat were functionally isolated from dorsal root filaments. The L7 and S1 ventral roots were split into 25 to 50 “natural” subdivisions, each of which was stimulated at 50 to 100 Hz for 1.5 s. The subdivided filaments were segregated into two groups; those which when stimulated elicited discharge from the Ib afferent (“excitatory” filaments) and those which did not (“non-excitatory” filaments). In ten of eleven experiments, it was found that when all the excitatory filaments were separated out, concurrent stimulation of all the non-excitatory filaments failed to excite the tendon organ, even when these filaments generated over 90% of the muscle's peak tetanic tension. The response of a tendon organ to stimulation of just its excitatory filaments often exceeded its response to whole muscle stimulation. However, several exceptions to this finding were observed, indicating that some tendon organs are affected by “off-line” forces. In general, the present results lend strong support to the Houk and Henneman model.
... the late Nicolai Bernstein, Israel Gelfand and Michael Tsetlin; Bernstein's student,... more ... the late Nicolai Bernstein, Israel Gelfand and Michael Tsetlin; Bernstein's student, Victor Gurfinkel; Ludmila Kudina and Raisa Person; Yuri Arshavsky, Michael Berkinblit, Tatiana Deliagina, Anatole Feldman, Olga Fookson, Sergei Kashin, Yakov Kots, Andrey Kulagin, Mark ...
Determinism is the metaphysical doctrine that the whole of world history is uniquely fixed by law... more Determinism is the metaphysical doctrine that the whole of world history is uniquely fixed by laws of nature and initial conditions. In science, “deterministic ” is an epithet of theories or of laws that describe the temporal behavior of physical systems as strictly regular. Description of the Theory What is Determinism? To a first approximation, determinism is the claim “that there is at any instant exactly one physically possible future ” ([1] p 3). As such, determinism is a metaphysical doctrine about the course of the world as a whole, rather than a scientific theory. The French mathematician P. S. Laplace famously and vividly formulated metaphysical determinism in the early nineteenth century: “An intelligence that, at a given instant, could comprehend all the forces by which nature is animated and the respective situation of the beings that make it up, if moreover it were vast enough to submit these data to analysis, would encompass in the same formula the movements of the gre...
Tienda online donde Comprar Encyclopedia of Neuroscience al precio 1994,00 € de Binder, Marc D. |... more Tienda online donde Comprar Encyclopedia of Neuroscience al precio 1994,00 € de Binder, Marc D. | Hirokawa, Nobutaka | Windhorst, Uwe, tienda de Libros de Medicina, Libros de Neurologia - Neurologia general
The ionic molecules nitrate (NO 3 À) and nitrate (NO 2 À) were believed to be detrimental to huma... more The ionic molecules nitrate (NO 3 À) and nitrate (NO 2 À) were believed to be detrimental to human health, but recently are considered to be beneficial on the nitric oxide regulation in human body. The transporter protein, Nark, efficiently moves the NO 3 À and NO 2 À across the membrane to maintain the homeostatic level of the two ionic molecules as vital metabolites. Based on experimental evidence, Zheng and coworkers proposed a NO 3 À /NO 2 À exchange mechanism through the Nark. Here, we perform molecular dynamics simulations to probe the protein conformational changes associated with the NO 3 À /NO 2 À exchange cycle. Umbrella sampling is utilized to investigate the free energy profiles of NO 3 À and NO 2 À migrations.
The results of this study and its precedents suggest that the tetrapartite classification scheme ... more The results of this study and its precedents suggest that the tetrapartite classification scheme might have universal applicability to at least the muscle units of cat hindlimb muscles and perhaps any mammalian muscle in which fiber typing reveals the presence of FG, FI, FOG, and type SO fibers. A possible exception to this generalization involves a small (n = 18) but thoroughly examined sample of muscle units from the first deep lumbrical muscle of the cat's foot, which led Kernell et al. (30) to conclude that the FF, FR, and S classification scheme was not directly applicable to that muscle. However, histochemical fiber typing is not yet available for that muscle. Furthermore, more extensive sampling, use of a different stimulation regime in the fatigue test, and a more detailed analysis of the sag property might well reveal that the tetrapartite classification scheme is indeed appropriate for units of cat foot muscles.
Cross-correlation techniques have been used to study the responses of muscle spindle afferents fr... more Cross-correlation techniques have been used to study the responses of muscle spindle afferents from the soleus muscle of the cat to twitch contractions of single motor units. 2. Cross-correlograms (post-stimulus time histograms) were used to give the frequency of occurrence of a receptor spike at various times following the initiation of a motor unit contraction together with a display of the average twitch tension wave form. 3. The cross-correlograms revealed that the contraction of a single motor unit can be an effective stimulus to a spindle receptor and may induce afferent firing pattern alterations similar to those observed with whole muscle contraction. 4. The cross-correlograms also revealed quantitative differences in the response of a receptor to contraction of different motor units and to contraction of the same motor unit at different lengths. These differences reflect subtle changes in receptor deformation developed by the twitch of a motor unit under different conditions and by the twitches of different motor units. The results are consistent with anatomical data on the number and distribution of motor units and receptor organs in cat soleus. 5. These findings emphasize that rather than simply acting as generalized force or length sensors for the muscle as a whole, each receptor's spike train carries information about the state of a particular set of motor units.
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