Flashcards in Cranial nerves II Deck (17):
where is the oculomotor nuclear complex?
rostral midbrain, ventral to the PAG
where is the trochlear nucleus?
where is the abducens nucleus?
where is the facial nucleus?
the oculomotor complex is made up of what nuclei? what fibers do they carry?
1. oculomotor nucleus - motor 2. Edinger-Westphal nucleus - parasympathetic
what are the symptoms of a CN 3 lesion?
wrinkled forehead, raised eyebrow, ptosis, dilated pupil, downward abducted eye
what are the components of the parasympathetic pupillary light (constriction) reflex?
1. ganglion cells axons of retina go to ipsilateral and contralateral pretectal areas of midbrain 2. ganglion cell axons synapse at pretectal neurons that project bilaterally to EWN to stimulate preganglionic parasympathetic cell bodies 3. axons from parasympathetic cell bodies run via CN 3 to terminate in ciliary ganglion
what are the components of the sympathetic pupillary (dilation) reflex?
1. cell bodies of hypothalamus descend to spinal cord and terminate at T1 2. preganglionic sympathetic neurons in lateral horn of spinal cord give rise to axons that enter sympathetic trunk 3. sympathetic trunk neurons ascend to superior cervical sympathetic ganglion to synapse with postganglionic sympathetic neurons which ascend via the internal carotid to innervate Muller's muscle, dilator pupillae
where does the trochlear nerve leave the brainstem?
just inferior to inferior colliculus
what are the courses of axons leaving the abducens nucleus?
1. motor neurons forming abducens nerve 2. interneurons joining the medial longitudinal fasciculus and ascending to rostral midbrain and terminating in oculomotor nucleus to innervate MR muscles
what minimizes horizontal diplopia resulting from an abducens nerve lesion?
turning head in direction of lesion
what is the result of a lesion to an abducens nucleus?
deficit in ipsilateral LR and contralateral MR
what nucleus is responsible for conjugate horizontal eye movement? what is the higher center modulation?
1. abducens nucleus 2. frontal and parietal motor eye fields (via reticular formation)
what is the mechanism of internuclear opthamalmoplegia? what is the result? does it affect convergence?
1. lesion to one MLF disconnecting the abducens nucleus and the contralateral oculomotor nucleus 2. deficit in conjugate horizontal eye movement 3. does NOT affect convergence
what controls LMNs during conjugate horizontal eye movement? convergence?
1. conjugate horizontal eye movement - MLF 2. convergence - higher brain centers via reticular formation
what is the deficit involved in one-and-a-half syndrome? what is the cause?
1. ipsilateral lateral gaze paralysis and internuclear opthalmoplegia 2. lesion involving one entire abducens nucleus and MLF fibers from contralateral abducens nucleus