chapters 9 10 single

8/14/2019 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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