Motoneurone
The motoneurones constitute the exit point of the central Nervous system or the final way of any driving act. The cellular bodies of the motoneurones are located either in the cerebral Tronc, or in the ventral Corne of the gray Substance of the Spinal-cord. Each motoneurone has a Axone which leaves the central nervous system for innerver the Muscle fibers of a Muscle. The unit consisted a motoneurone and muscle fibers that it innerve constitutes a driving Unité.
One distinguishes three types of motoneurones: the motoneurones alpha , which innervent the muscle fibers responsible for the contraction, the motoneurones gamma , which innervent the spindles neuromusculaires, thus adjusting their sensitivity to the stretching, as well as the motoneurones beta , which innervent the two types of fibers.
Projections of the motoneurones
The motoneurones are connected to two standard of cells. Via their Axon, they innervent muscle fibers of their driving unit. Before leaving the Spinal-cord, the axon of the motoneurones emits collateral which innerve the Cellules of Renshaw, which represent a category of spinaux interneurones. The neuro-transmitter used by the motoneurones is the Acetylcholine.
Receivers expressed by motoneurones
Like all the neurons of the central nervous system, the motoneurones are equipped with receivers. The exiting synapses contain receivers with the Glutamate (AMPA, Kaïnate, NMDA). The inhibiting synapses contain receivers with GABA and the Glycine. In addition to these receiving ionotropes, the motoneurones express Récepteurs métabotropes activated by the Glutamate, the Noradrénaline, the Sérotonine, the Acetylcholine.
Techniques of study
Because of relatively high size of their summoned (about 50µm diameter), the motoneurones were the first nervous cells studied with intracellular electrodes. These experiments carried out during the years 1950 on cats anesthesias made it possible to characterize the principal ways Réflexe S of the Spinal-cord (they are primarily work of John Carew Eccles, Nobel Prize of physiology and medicine in 1963). For ethical reasons as for the scientific little of interest that it causes, this experimental approach is in the process of disappearance. Since the years 1980, the motoneurones are studied on preparations in vitro of sections of spinal-cord or of course of the cultures of cells taken in the spinal-cord. These models of study make it possible to use in parallel of the techniques such as the electrophysiology, the Pharmacologie, the Microscopie, the Immunohistochimie.
Related articles
- driving Cortex
- movement
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