chapters 9 10 single
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Midbrain
Cerebral peduncle Oculomotor nerve
Trochlear nerveFrom the dorsal
surface, curves
around
Optic tract
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Midbrain Subdivisions
Tectum Superior/inferior
colliculi
Tegmentum Ascending/descending
tracts Nuclei
Basal portion Substantia nigra
Pigmented
Cerebral peduncle
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Inferior Colliculus: Afferents
Lateral lemniscus Terminate both ipsi and
contralateral
Contralateral inferior
colliculus Ipsilateral medial
geniculate body
Auditory feedbackpathway
Primary auditorycortex
Cerebellum
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Midbrain: Efferents Medial geniculate body
Audition
Contralateral inferiorcolliculus
Superior colliculus Head/eye orienting
Nucleus of lateral
lemniscus Auditory feedback
Cerebellum Localize sound sources
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Fibers of passage: Inf. Coll. Level
Superior cerebellar
peduncle Brachium conjunctivum
Medial lemniscus
Trigeminal lemniscus Spinothalamic tract Lateral lemniscus Medial longitudinal
fasciculus (MLF) Central tegmental tract
Basal ganglia/midbrain toinferior olive
Rubrospinal tract
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Midbrain Nuclei: Inf. Coll. Level
Mesencephalicnucleus oftrigeminal nerve
Unipolar neurons
Proprioception of
mastication Nucleus of
trochlear nerve
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Midbrain Nuclei: Inf. Coll. Level Pedunculopontine and lateral
dorsal tegmental nuclei
Cholinergic Walking
Supranuclear palsy
Degenerative CNS disease
Slowing of movement
Reduced control of:
Walking
Balance
Swallowing Speaking
Eye movements
Eventually
wheelchair/bedridden Tau proteins build up in specific
nuclei
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Midbrain Nuclei: Inf. Coll. Level Locus Ceruleus
Nucleus pigmentosus
Pigmented neurons Melanin
Loss of these neurons inParkinsons
Projects widely throughout CNS Thalamus
Hypothalamus
Basal ganglia
Cerebellum
Spinal cord
Sensory nuclei of brainstem
Also plays a role in:
Respiration
REM sleep
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Cerebral Peduncle Divisions Carries fibers from
cortex to subcorticalstructures
Corticopontine Lateral
Parieto/occipito/temporo-pontine projections
Medial Fronto-pontine projections
Corticospinal Continues to pyramids
Corticobulbar Cranial nerve nuclei
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Substantia Nigra Afferents
Neostriatum(caudate/putamen)
Largest
Cerebral cortex
Minor
Efferents Neostriatum
Sensorimotor and limbic
Cerebral cortex
Limbic cortex
Akinesia
Absence of movement
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Substantia Nigra Regulates motor
activity
Parkinsons
diseaseTremor, rigidity,
slowness of motoractivity
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Substantia Nigra Pigmented: dopamine
Non-pigmented: cholinergic or GABAergic
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Mesencephalic DopaminergicSystem
Ventral tegmental
area of Tsai Retrorubral cell
group
Mesostriatal Striatum
Mesoallocortical Amygdala, olfactory
tubercle
Mesoneocortical All lobes
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Superior colliculus
Afferents Cerebral cortex
Mostly occipital (visualcortex)
FEF frontal eye fields
Retina
Spinal cord
Spinotectal
Pain
Inferior colliculus
Orienting to sound
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Superior colliculus
EfferentsTectospinal
Neck movements
Tectopontocerebellar tract Orienting responses
to cerebellumTectothalamic tract
Lateral geniculate
nucleus Pulvinar
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Lesions of the Superior Colliculus
UnilateralNeglect of contralateral visual field
Heightened response to ipsilateral visual field
Deficits in tracking moving objects
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Superior Colliculus
Overlapping visual and auditory receptivefields
Orienting responses
Visual drives auditory
Localization
Resolution
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Tegmentum: Nuclei
Red nucleus
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Red Nucleus
AfferentDeep cerebellar
nuclei
Volitional tremor Tremor when
moving only
Cerebral cortex Motor/premotor
cortex
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Red Nucleus Efferent
Spinal cord Facilitates flexor motor
neurons
Inhibits extensor motor
neurons Just like corticospinal tract
Cerebellum
Inferior Olive
Major projection in humans
Then projects tocerebellum
Feedback circuit
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Red Nucleus
Main function: movementLinks cortex, cerebellum, spinal cord
Lesions of red nucleus
Contralateral tremor
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Tegmentum: Nuclei Oculomotor nucleus
Afferent
Cerebral cortex INC- Interstitial nucleus of
Cajal Upward gaze
RiMLF rostral interstialnucleus Downward gaze
Pretectal olivary nucleus Pupillary light reflex
Pons/Medulla Cranial nuclei involved in
eye movements
Cerebellum
Regulate eye movements
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Lesions of Oculomotor Nerve A outside
brainstem Ipsilateral eye
B cerebral
peduncle andfibers Ipsilateral eye
Contralateral motor
C Red nucleusand fibers Ipsilateral eye
Contralateral motor
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Pupillary Light Reflex
Ipsilateral pupilDirect light reflex
Contralateral pupil
Consensual lightreflex
Due to pretectalnucleus projectingto both oculomotor
nuclei
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Optic Nerve Lesion
AbolishesDirect light reflex
Consensual light
reflex
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Oculomotor Nerve Lesion
AbolishesDirect light reflex
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Marcus Gunn Pupil
Paradoxical pupildilation to light
Note: this is
because there islittle/no light
going to the othereye with intactoptic nerve
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Control of Saccadic Eye
Movements
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Frontal Eye Fields
20
20
Saccades
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Microstimulation
Inject current directly
Activates neurons High temporal and
spatial resolution
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Motor Field
1
Microstimulation of FEF
75A
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Oculomotor Control of Spatial
Attention
Motor field Activity, i.e. a motor plan deploys spatial
attention to the location the eyes would
move to
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