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The corticobulbar (or corticonuclear) tract is a two-neuron white matter motor pathway connecting the motor cortex in the cerebral cortex to the medullary pyramids, which are part of the brainstem's medulla oblongata (also called "bulbar") region, and are primarily involved in carrying the motor function of the non-oculomotor cranial nerves, like muscles of the face, head and neck.
The pyramidal tracts include both the corticobulbar tract and the corticospinal tract.These are aggregations of efferent nerve fibers from the upper motor neurons that travel from the cerebral cortex and terminate either in the brainstem (corticobulbar) or spinal cord (corticospinal) and are involved in the control of motor functions of the body.
The pyramidal tracts (corticospinal tract and corticobulbar tracts) may directly innervate motor neurons of the spinal cord or brainstem (anterior (ventral) horn cells or certain cranial nerve nuclei), whereas the extrapyramidal system centers on the modulation and regulation (indirect control) of anterior (ventral) horn cells.
The genu is the bend, or flexure in the V of the internal capsule. It is formed by fibers from the corticobulbar tract.The fibers in this region are named the geniculate fibers that carry upper motor neurons from the motor cortex to cranial nerve nuclei that mainly govern muscle motion of the head and face.
It receives upper motor neuron innervation directly via the corticobulbar tract. This nucleus gives rise to the branchial efferent motor fibers of the vagus nerve (CN X) terminating in the laryngeal , pharyngeal muscles, and musculus uvulae ; [ 3 ] as well as to the efferent motor fibers of the glossopharyngeal nerve (CN IX) terminating in the ...
In neuroanatomy, the medullary pyramids are paired white matter structures of the brainstem's medulla oblongata that contain motor fibers of the corticospinal and corticobulbar tracts – known together as the pyramidal tracts. The lower limit of the pyramids is marked when the fibers cross .
This leads to facial weakness that spares various muscles in the face depending on the type of paralysis. The discrepancy of the weakness between the upper and lower facial muscles are due to the bilateral corticonuclear innervation from the upper facial muscles and contralateral corticonuclear innervation to the lower facial muscles.
corticobulbar tract: from the motor cortex to several nuclei in the pons and medulla oblongata: Involved in control of facial and jaw musculature, swallowing and tongue movements. colliculospinal tract (tectospinal tract) from the superior colliculus to lower motor neurons: Involved in involuntary adjustment of head position in response to ...