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52 Cards in this Set
- Front
- Back
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Landmarks for the midbrain
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– Four colliculi [dorsal side]
– Cerebral peduncles [central site] |
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Components of the brain
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– Ascending/descending tracks
– Cranial nerve nuclei – Connections to the cerebellum – Intrinsic systems |
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Tectum
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– The roof of the 4th ventricle
– Prominent in midbrain [inferior + superior coliculi] – In pons and medulla is superior and anterior medullary vela [form the roof of the fourth ventricle] |
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Tegmentum
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– Area anterior to the ventricular space
– Contains: reticular formation nuclei, cranial nerve nuclei and fibers/tracks and ascending/descending tracts – Contains midbrain and Medulla |
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Base
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– Contains: crus cerebri, basal pons, medullary pyramids
– Mostly motor fibers – anterior surface of the brain – Contains corticospinal, corticobulbar and corticalpontine fibers |
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The corticobulbar tract runs between
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The cortex and brainstem ["bulb"]
– Originates mainly in head and face area of precentral gyrus – Terminates on cranial nerve motor nuclei in brainstem |
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Pathway to brainstem: corticobulbar tract
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– Descends through Corona radiata
– Descends through genu and anterior part of posterior limb of internal capsule – Travels with corticospinal tract through middle 3/5 of crus cerebri (ant portion of cerebral peduncle) |
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Which cranial nerve motor nuclei does the corticobulbar tract terminate on
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– Nucleus ambiguous
– Motor nucleus of V – Spinal accessory nucleus – Hypoglossal nucleus – Facial motor nucleus – Cranial nerve nuclei 3, 4, 6 |
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Nucleus ambiguous contains the cell bodies of which cranial nerves
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IX, X,XI = the nerves that run through the jugular foramen
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All of the cranial nerve motor nuclei supplied by the corticobulbar tract receive bilateral innervation except
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Facial motor nucleus
– Bilateral innervation to rostral part of nucleus – Contralateral innervation to the caudal part of the nucleus |
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The rostral part of the facial motor nucleus projects to
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Upper facial muscles
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The caudal part of the facial motor nucleus projects to
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Lower facial muscles
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The spinal accessory nucleus projects to
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– Ipsilateral projections for sternomastoid
– Mostly contralateral projections for trapezius |
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All the cranial Nebhut prayers supply by the quarter call Overcheck except which three
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Cranial nerves 1,2, 8
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The hypoglossal nuclei receive bilateral projection but is crossed for which muscle
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Genioglossus
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Functions of the media longitudinal fasciculus
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– Contains fibers that arise from parts of all vestibular nuclei
– Connect vestibular nuclei with the nuclei of cranial nerves 6, 4, 3 (innervation of extraoccular m.) – Provides for conjugate movements of the eyes, coordinated with movements of the head, to maintain visual fixation |
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Vestibulo–ocular reflex
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A small rotation of the head is accompanied by movement of the eyes through the same angle but in the opposite direction
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What are the four vestibular nuclei
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– Superior
– Lateral – Media – Inferior |
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General somatic efferents
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Innervates the skeletal muscle derived from somites
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Special visceral efferent
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Enervate Billadeau muscle derived from brachial arches
A.k.a. Rachel a friend |
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General visceral efferent
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visceral motor [= parasympathetic]
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General visceral afferent
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Sensation from the viscera of the head and neck
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Special visceral afferent
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Taste
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General somatic afferent
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General sensation from head and neck
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Special somatic afferent
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Hearing and balance [CN 8]
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Cranial nerve nuclei found in midbrain
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– Mesencephalic nucleus of V [GSA]
– Edinger-Westphal nucleus of III [GVE] – Oculomotor and trochlear nuclei [GSE] |
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Cranial nerve nuclei found in pons
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– Chief nucleus of V [GSA]
– Superior salivatory of VII and inferior salivatory of IX [G VE] – Motor nucleus of V and facial nucleus [SVE] – Abducens nucleus [GSE] |
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Cranial nerve nuclei found in junction between pons and medulla
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Vestibulo-cochlear nucleus [SSA]
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Cranial nerve nuclei found in the medulla
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– Spinal nucleus of V , IX and X [GSA]
– Solitarius nucleus of VII, IX and X [SCA] – taste – solitarius nucleus of IX and X [GVA] – Dorsal motor nucleus of Vegas [GVE] – Ambiguus nucleus of IX and X, spinal accessory nucleus [SVE] – Hypoglossal nucleus [GSC] – Tongue movement |
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What are some examples of general sensory efferents
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– Eye movement
– Tongue movement |
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Example of special visceral afferent
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Taste
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Example of special sensory afferent
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Hearing and balance
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Parasympathetic are considered
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General visceral inference
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which columns are located medial to sulcus limitans in brainstem
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Efferent motor columns
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Which columns are located lateral to sulcus limitans in brainstem
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Sensory afferents
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The visceral motor parasympathetic branch of the oculomotor nerve : Function
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– Supplies ciliary and constrictor pupillae muscles
– Constricts pupil and accommodates lens – If damage will cause dilated pupil |
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Main oculomotor nucleus
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– Rostral midbrain [anterior part of periaqueductal gray]
– Efferents pass anteriorly through red nucleus |
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Edinger – Westphal nucleus
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– Parasympathetic visceral motor part of oculomotor nucleus
– Posterior to main oculomotor nucleus – Synapse in ciliary ganglion |
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Location of trochlear nucleus and its fibers
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– Nucleus in caudal midbrain [anterior part of periaqueductal gray]
– efferent fibers past posteriorly around central gray – decussate in superior medullary velum – Emerge just caudal to inferior caliculus [Posterior aspect of brainstem] |
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Location of abducens nucleus and its fibers
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– Nucleus in posterior part of caudal pons
– Efferent fibers pass anteriorly through pons and emerged at Pontomedullary Junction |
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What are the horizontal eye movements
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– Saccades
– Pursuit - VOR |
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MLF
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– Ascending tract
– Connects CN 6 on one side with CN 3 on opposite side |
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Paramedian pontine reticular formation (PPRF)
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– Horizontal gaze system
– Located in pons – When stimulated will activate ipsilateral abducens nucleus --> ipsilateral LR muscle – MLF also activated --> contralateral oculomotor nucleus --> CN III --> contralateral MR muscle (gaze) |
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What simulates PPRF?
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Contralateral frontal eye field [area 8]
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Pathway from cortex --> PPRF in a saccadic eye movement
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1) Frontal eye field
2) Lateral geniculate nucleus of thalamus (contralateral) --> Primary visual cortex + superior colliculus 2) primary visual cortex --> Frontal eye field and visual association cortex (contralateral side) --> sup colliculus 3) superior colliculus --> PPRF (ipsilateral) --> reflexive or volitional saccades --> contraction of contralateral MR and ipsilateral LR |
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Pursuit: function
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Symbolizes image on the fovea during slow movements of the object or during locomotion
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Four inputs necessary for pursuit
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– Primary visual cortex [which objects]
– Frontal eye field [move eye] – Cerebellum [where at my relation to object] – Vestibular nuclei [where I in space] |
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Input relay center for pursuit
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Abducens nucleus
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Pathway from cortex --> eye for pursuit
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1) Frontal eye field and visual cortex
2) Pontine nuclei 3) Cerebellum 4) Vestibular nuclei 5) Abducens nuclei 6) Lateral rectus muscle or oculomotor nuclei to medial rectus |
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Functions of vestibular system
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– Regulation of posture
– Coordination of head and eye movement |
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Function of this vestibulo-ocular reflex
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Reflects adjusts eye movement to head movement
– Aim is to keep image stable on retina |
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Pathway for VOR
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1) input from semicircular Canal
2) to vestibular ganglion --> vestibular nuclei 3) to abducens nuclei 4) synapse on MLF and abducens nerve 5) MLF --> oculomotor nuclei --> CN III --> MR muscle 5) CN VI --> lateral rectus |
