Brainstem and Cerebellum: Medulla, Pons, Midbrain, Reticular Formation, Arousal, Vision, Hearing, Norepinephrine, Serotonin, Dopamine, Sleeping, Dreaming, REM, Cranial Nerves, Motor Control, by Joseph R

Author:Joseph, R. [Joseph, R.]
Language: eng
Format: epub
Publisher: University Press
Published: 2011-11-08T16:00:00+00:00

Lesions of the vestibular receptors, their nerves, or central connections cause abnormal sensations of movement, vertigo, nausea, tendencies to fall, dizziness, and motion sickness, etc.

The vestibular system also provides information about the position of the head and correlates head and eye movements with somatic muscle activity. Together with the descending medial longitudinal fasciculus (MLF) and vistibulospinal tracts, the vestibular system is able to mediate the postural reflexes. In part it is able to accomplish this via rich interconnections with those cranial nerve nuclei (via the MLF) which subserve eye movement (nerves VI, IV, & III). Disease involving these tissues can therefore cause nystgamus.

Following injuries to this system, patients may complain of to-andfro or up-and-down movements of body, or floors, and noted that the walls seem to tilt or sink or rise. When walking there may be feelings of unsteadiness such that they veer to one side. Or there may be a feeling of being pulled or drawn--a feeling of impulsion. There also may be a disinclination to walk (particularly during an attack), a tendency to list to one side, and the condition may be aggravated by riding in a vehicle. Some disturbances may occur only for a few seconds, or after lying down or sitting up, turning, etc. When less severe the patient may merely veer to one side while walking.

The vestibular system is also concerned with eye movement, for it is also via ocular signals that the position of the head and body in space can be determined. Hence, vestibular dysfunction can include difficulty focusing or fixating on objects while walking, or when the object is moving. This is due to a loss of stabilization of ocular fixation by the vestibular system during body movement and is caused by an inability to integrate visual with vestibular input. These functions are normally made possible through rich interconnections (via the MLF) between the vestibular system and the 6th, 4th and 3rd nerves which subserve eye movement, as well as the bilateral interconnections between these regions and the cerebellum.

ORAL-FACIAL MOVEMENT & SENSATION THE 7th CRANIAL (FACIAL) NERVE

The 7th nerve, and the brainstem nuclei which it innervates, is concerned with facial movement, including elevation of the eyebrows, retraction of the lips, closure of the auditory canals, as well as with gustatory sensation. Injuries to the 7th nerve can therefore produce a lip retraction, eyebrow lifting or eyelid closure paralysis; i.e. Bell’s palsy. Patients have difficulty or are unable to wrinkle the forehead, purse their lips and show their teeth,and the corner of the mouth may droop.

In addition, whereas cranial nerves 9 and 10 innervate the taste buds of the posterior 3rd of the tongue, cranial nerve 7 innervates the anterior 2/3s. Hence, a lesion of the 7th nerve can result a disturbance of taste sensation.

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.