Showing papers on "Motor neuron published in 1969"

Intraneuronal Conglomerates in Sporadic Motor Neuron Disease: A Light and Electron Microscopic Study

Abstract: IN THE ADULT, motor neuron disease or amyotrophic lateral sclerosis can be subdivided into several groups on the basis of clinical, pathologic, and epidemiologic features. 1 The histologic changes observed in the classic sporadic cases include nonspecific degeneration and loss of motor neurons in the spinal cord, brain stem, and cerebral cortex. Demyelination of the pyramidal tracts often accompanies the neuronal losses. 2 A familial variant further characterized by demyelination of the posterior columns and spinocerebellar tracts has been reported. 3 In a few residual motor neurons from these cases, Hirano et al 4 described accumulations of hyalinized material, occasionally with acidophilic cores that resemble Lewy bodies. In still another variant, the amyotrophic lateral sclerosis and Parkinsonism-dementia complex on Guam, neurofibrillary tangles have been observed in the anterior horn cells. 5 This report presents light and electron microscopic observations from an unusual sporadic case of motor neuron disease characterized by

Intracellular activity in cricket neurons during generation of song patterns

Abstract: During production of song patterns by the semi-isolated CNS of Gryllus campestris, intracellullar recordings were made in fibers of the mesothoracic ganglion, including synaptic areas of identified wing opener and closer motor neurons. The normal calling song pattern and some transitional songs toward courtship and toward aggression were generated by the CNS in the absence of any phasic sensory timing (Figs. 1, 4). Intracellular activity of the opener motor neurons was characterized by an absence of events in the interchirp interval, an EPSP underlying each burst, and an IPSP following the burst if the closer motor neurons were to be activated (Fig. 1). Intracellular activity of the closer motor neurons was characterized by an absence of events in the interchirp interval, an IPSP immediately following the onset of the opener motor neuron burst, and an EPSP after the IPSP (Figs. 2, 3). Units were found which fired in a burst during the period when both the opener and closer motor neurons were inhibited (Fig. 5). Complementary sets of units were found which displayed an oscillation of activity at the chirp rhythm but not at the pulse rhythm (Fig. 6). Gaps in the calling song were observed whose characteristics indicated that motor neuron activity was neither required for, nor effective in, resetting the chirp timing oscillator (Fig. 8). A possible model for the song generating mechanism is outlined.

Interneurons in the central nervous system of flies and the start of flight

Abstract: 1. The mesothoracic legs provide the major thrust for the jump which occurs at the beginning of flight. However, Calliphora vicina missing their mesothoracic legs can still jump. They do not jump as well as flies missing only the metathoracic legs, and neither class of amputees jumps as well as intact animals. 2. The tergotrochanteral muscles of C. vicina are the principle extensors of the mesothoracic legs, and are innervated by one motor neuron each (Fig. 1). These motor neurons are driven by a pair of interneurons, which originate in the supraoesophageal ganglion and descend through the cervical nerve cord to synapse with the motor neurons in the thorax (Figs. 2, 3B, 3C). These interneurons can be stimulated electrically in the optic lobes of the brain (Fig. 3A). Together with the tergotrochanteral motor neurons, these interneurons are homologous with the giant fibers described by Power (1948). 3. These same interneurons innervate motor neurons of extensors of the metathoracic legs (Fig. 2), and perhaps other units. The actual muscles involved have not been identified. 4. The innervation of the tergotrochanteral muscles and the observations on the jumping ability of flies missing various legs support the idea that these muscles are the main starter of the flight motor.

Certain Histological and Anatomical Features of the Central Nervous System of a Large Indian Spider, Poecilotheria

Abstract: SYNOPSIS Some of the finer details of the anatomical organization of the subesophageal ganglion of the spider, Poecilotheria sp were studied in Palmgren silver-stained sections at the light microscopic level The ganglionic mass is differentiated into a central fibrous core and a peripheral layered mass of cellular cortex The neuropile is heterogeneous, consisting of both diffuse and glomerular types, and is considered the primary place for integration The dorsal region is motor, and the ventral is sensory The processes of motor cells and endings of sensory neurons are restricted mostly to a single ganglion Each large motor neuron possesses a long stem-process, short and highly branched dendritic ramifications, and a smooth, unbranched axon Larger interneurons are more diversified, and extend from one to several ganglia These are of ascending or descending or even decussating types Smaller interneurons are mostly restricted to one or a few ganglia On the basis of this organization the probable synaptic junctions between neurons are discussed

Speed of Contraction of Skeletal Muscle: The Effect of Hypoactivity and Hyperactivity

Abstract: PREVIOUS work from this laboratory indicates that there is a relation between the speed of contraction of a motor unit and the size of the motor neuron innervating it. 1,2 Motor units which contract rapidly and develop large amounts of tension are innervated by large motor neurons, whereas motor units which contract slowly and develop small amounts of tension are innervated by small motor neurons. Moreover, the size of a motor neuron determines its susceptibility to discharge: the smaller an anterior horn cell, the lower its threshold for excitation. 3 It follows that the contraction speed of muscle fibers may be a function of the amount of contractile activity they perform. The available evidence 1-3 suggests that muscle fibers which are used intensively have slow speeds of contraction. If this inference is correct, experimental interventions which alter the amount of activity or usage of a muscle should produce changes in