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Two of the cranial nerves show chiasmas: (1) the chiasma of the optic tract (i.e., cranial nerve II), which originates from the eyes and inserts on the optic tectum of the midbrain; and (2) the trochlear nerve (i.e., cranial nerve IV), which originates in the ventral midbrain and innervates one of the six muscles that rotate the eye (i.e., the ...
The muscle, skin, or additional function supplied by a nerve, on the same side of the body as the side it originates from, is an ipsilateral function. If the function is on the opposite side to the origin of the nerve, this is known as a contralateral function. [9]
On the contralateral side (the one that bears all the weight), the flexors relax and the extensors contract to stiffen the leg since it must suddenly support the entire weight of the body. At the same time, signals travel up the spinal cord and cause contraction of the contralateral muscles of the hip and abdomen to shift the body’s center of ...
Due to the small size of the arteries in the area, the most common cause of a local lesion is an infarction due to lipohyalinosis and hypertension. Like other small arteries of the brain, these vessels are vulnerable to microemboli , especially those generated due to turbulence or low-flow states in those with artificial heart valves or ...
The olivocochlear system is a component of the auditory system involved with the descending control of the cochlea.Its nerve fibres, the olivocochlear bundle (OCB), form part of the vestibulocochlear nerve (VIIIth cranial nerve, also known as the auditory-vestibular nerve), and project from the superior olivary complex in the brainstem to the cochlea.
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.
In Millard–Gubler syndrome, a unilateral softening of the brain tissue arising from obstruction of the blood vessels of the pons involving sixth and seventh cranial nerves and the corticospinal tract, the VIth nerve palsy and ipsilateral facial paresis occur with a contralateral hemiparesis. [8]
Superior alternating hemiplegia (also known as Weber syndrome) has a few distinct symptoms: contralateral hemiparesis of limb and facial muscle accompanied by weakness in one or more muscles that control eye movement on the same side. [2] Another symptom that appears is the loss of eye movement due to damage to the oculomotor nerve fibers.