Corticobulbar tract

Brain: Corticobulbar tract
Components and location of the corticobulbar tract.
Latin	tractus corticonuclearis
NeuroNames	ancil-371

The corticobulbar (or corticonuclear) tract is a white matter pathway connecting the cerebral cortex to the brainstem. The term "bulbar" referrers to the brainstem, as "bulb" was a historical term meaning the area currently called the brainstem.

The 'bulb' is an archaic term for the medulla oblongata. In clinical usage, it includes the pons as well.

Function

The muscles of the face, head and neck are controlled by the corticobulbar system, which terminates on motor neurons within brainstem motor nuclei. This is in contrast to the corticospinal tract, which connects the cerebral cortex to spinal motor neurons, and controls movement of the torso, upper and lower limbs.

The corticobulbar tract runs through the genu of the internal capsule and a few fibers in the posterior limb of the internal capsule, as it passes from the motor cortex down through to the brainstem.

The corticobulbar tract innervates cranial motor nuclei bilaterally with the exception of the lower facial nuclei which is innervated only contralaterally (below the eyes) and CN XII, which is innervated contralaterally as well. Among those nuclei that are bilaterally innervated a slightly stronger connection contralaterally than ipisilaterally is observed. The corticobulbar tract directly innervates the nuclei for cranial nerves V, VII, XI, and XII, and indirectly innervates nuclei for nerves III, IV, and VI via interneurons. It also contributes to the motor regions of nerves X and IX in the nucleus ambiguus.

External links

• Brainstem at UWisc 07CNXII
• http://thebrain.mcgill.ca/flash/i/i_06/i_06_cl/i_06_cl_mou/i_06_cl_mou.html

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