Function
The corticobulbar tract is composed of the upper motor neurons of the cranial nerves. 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 in which the cerebral cortex connects to spinal motor neurons, and thereby controls movement of the torso, upper and lower limbs.
The corticobulbar tract innervates cranial motor nuclei bilaterally with the exception of the lower facial nuclei which are innervated only unilaterally (below the eyes) and cranial nerve XII which is innervated unilaterally as well. Both the lower part of cranial nerve VII and XII are innervated by the contralateral cortex. Among those nuclei that are bilaterally innervated a slightly stronger connection contralaterally than ipsilaterally is observed. The corticobulbar tract directly innervates the nuclei for cranial nerves V, VII, XI, and XII. It does not innervate nuclei for nerves III, IV, and VI because these are mediated by cortical projections and yoked together by the MLF, medial longitudinal fasciculus. The corticobulbar tract also contributes to the motor regions of nerves X and IX in the nucleus ambiguus.
Read more about this topic: Corticobulbar Tract
Famous quotes containing the word function:
“The fact remains that the human being in early childhood learns to consider one or the other aspect of bodily function as evil, shameful, or unsafe. There is not a culture which does not use a combination of these devils to develop, by way of counterpoint, its own style of faith, pride, certainty, and initiative.”
—Erik H. Erikson (1904–1994)
“No one, however powerful and successful, can function as an adult if his parents are not satisfied with him.”
—Frank Pittman (20th century)
“Advocating the mere tolerance of difference between women is the grossest reformism. It is a total denial of the creative function of difference in our lives. Difference must be not merely tolerated, but seen as a fund of necessary polarities between which our creativity can spark like a dialectic.”
—Audre Lorde (1934–1992)