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Neuroanatomy > 7. Extrapyramidal sytem > Flashcards

7. Extrapyramidal sytem Flashcards

1
Q

The extrapyramidal system contains all the descending motor tracts EXCEPT…

A

Pyramidal system tracts:
- Lateral corticospinal
- Ventral corticospinal
- Corticonuclear

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2
Q

Importance of extrapyramidal system in domestic species

A

Dominates over pyramidal system

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3
Q

2 roles of the extrapyramidal system

A
  1. Antigravity support
  2. Spinal reflex recruitment for initiation of movements
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4
Q

What are the command centers of the extrapyramidal system

A
  • Cerebral cortex
  • Basal nuclei
  • Tegmentum (red nucleus)
  • Tectum (caudal and rostral colliculi)
  • Reticular centers (pontine, medullary, +- midbrain)
  • Vestibular nuclei
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5
Q

Name the extrapyramidal tracts

A
  • (cortico)RUBROspinal tract
  • Medial TECTOspinal tract
  • Pontine & medullary RETICULOspinal tract
  • Lateral & medial VESTIBULOlospinal tract
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6
Q

Cereberal cortex

In the extrapyramidal system, widespread regions of the cerebral cortex send projections where?

A

Other extrapyramidal command centers (basal nuclei + other brainstem nuclei)

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7
Q

Basal nuclei

Name the 5 and locate (slide 9)

A
  • Nucleus accumbens (1)
  • Caudate nucleus (2)
  • Putamen (5)
  • Globus pallidus (3, 4)
  • Claustrum (7)
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8
Q

Basal nuclei

Name the structures on slide 9

A
  1. Nucleus accumbens
  2. Caudate nucleus
  3. Medial globus pallidus
  4. Lateral globus pallidus
  5. Putamen
  6. Amygdala
  7. Claustrum
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9
Q

Basal ganglia

Define…
Neostriatum (striatum)
Lentifrom nucleus
Corpus striatum

A
  • NEOSTRIATUM: caudate + putamen
  • LENTIFORM NUCLEUS: putamen + globus pallidus
  • CORPUS STRIATUM: all basal nuclei + white matter of internal + external capsule
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10
Q

Basal nuclei

Among the basal nuclei, the role of the _ is unknown

A

Claustrum

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11
Q

Basal ganglia

NUCLEUS ACCUMBENS - Shape & location

A
  • Small
  • Ventral extension (nose) of caudate
  • Surrounds ventral portion of rostral horn of internal capsule
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12
Q

Basal nuclei

CAUDATE - Shape & location

A
  • Largest
  • C-shaped with large head and narrow body
  • Lateral to lateral ventricles
  • Medial to internal capsule
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13
Q

Basal nuclei

Medial GLOBUS PALLIDUS - Location

A
  • Medial to putamen
  • Lateral to internal capsule
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14
Q

Basal nuclei

PUTAMEN - Location

A
  • Lateral to globus pallidus
  • Medial to claustrum (separated from claustrum by thin external capsule)
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15
Q

Basal nuclei

CLAUSTRUM - shape & location

A
  • Long thin plate
  • Lateral to external capsule
  • From head of caudate (rostrally) -> ventral border of 3rd ventricle (caudally)
  • BARRIER between external capsule and insula
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16
Q

Basal nuclei

CAUDATE - Afferents vs efferents

A
  • A: Cerebral cortex + substantia nigra
  • E: globus pallidus
17
Q

Basal nuclei

Which is the only basal nuclei that sends efferents OUTSIDE of the basal nuclei (allows communication with rest of CNS)?

A

Medial globus pallidus

Globe trotter

18
Q

SUBSTANTIA NIGRA - location, neurons, components (slide 16)

A
  • Tegmentum (midbrain), dorsal to crus
  • Cell bodies contain melanin and synthesize dopamine (act on D1/D2-R)
  • Pars compacta, pars reticulata
19
Q

SUBTHALAMIC NUCLEI - Location, afferents, efferents (slide 17)

A
  • Ventral to thalamus
  • Ventromedial to internal capsule
  • A: Lateral globus pallidus
  • E: Medial globus pallidus (loop)
20
Q

6 keep points of how basal nuclei regulate movement

A
  • Thalamus is always facilitatory
  • Thalamus is under tonic inhibition by medial globus pallidus
  • Globus pallidus is inhibited by the neostriatum (disinhibition)
  • Substantia nigra + subthalamic nuclei always fire in the background, fine-tuning movement
  • Substantia nigra has dopaminergic neurons that inhibit (D2R) or activates (D1R) the neostriatum
  • Subthalamic nuclei for a loop with lateral and medial globus pallidus (allows communication between two parts of globus pallidus)
21
Q

Describe pathways of the extrapyramidal system DURING MOVEMENT

A
  • Activation of extrapyramidal neurons of the cereberal cortex –> activates neostriatum –> inhibits globus pallidus –> disinhibits thalamus –> MOVEMENT
  • Subsequent activation of the substantia nigra –> further activates neostriatum (D1R) –> further inhibits globus pallidus –> MORE movement
  • Feedback inhibition of the substantia nigra by neostriatum helps prevent excessive/constant movement
22
Q

Describe pathways of the extrapyramidal system DURING ABSENCE OF MOVEMENT

A
  • Substantia nigra sends inhibitory (D2R) outputs to neostriatum –> allows globus pallidus to inhibit thalamus
  • Inhibition of the lateral globus pallidus –> activates subthalamic nucleus –> further activates medial globus pallidus –> more inhibition of thalamus
23
Q

Causes and consequences of NIGROPALLIDAL ENCEPHALOMALACIA (NPE, chewing disease)

A
  • Necrosis of substantia nigra + globus pallidus
  • Yellow star thistle (centaurea solstitialis) or Russian knapweed (centaurea repens)
  • Spastic paresis of lips, pharyngeal, TMJ, facial muscles. Mouth partly opened, retracted lips, chewing motions
24
Q

RED NUCLEUS - location, afferents & efferents

A
  • Tegmentum, dorsal to substantia nigra, ventromedial to motor nucleus of CNIII
  • A: cortex, basal nuclei, cerebellum
  • E: olivary nucleus (loop to cerebellum), spinal cord (RS tract)

olive rouge

25
Q

Caudal & rostral COLLICULI - Loacation and roles

A
  • Tectum
  • Visual (rostral) and auditory (caudal) reflexes
26
Q

corticoRUBROSPINAL TRACT

A
  • Cortex -> internal capsule -> crus -> red nucleus (ipsi)
  • Immediately DECUSSATES in the midbrain->
  • Entire SC through LATERAL funiculus
  • Facilitatory to FLEXORS (protraction)
27
Q

Medial TECTOSPINAL TRACT (acoustic startle reflex)

A
  • Auditory info -> cochlear nuclei -> lateral lemniscus -> CAUDAL colliculus -> MNG (thalamus) -> auditory cortex
  • Auditory cortex -> ROSTRAL colliculus -> SC through medial tectospinal tract
  • Enables orientation of head, eyes, body in respose to sounds
28
Q

2 RETICULOSPINAL TRACTS

A
  • MEDULLARY: LATERAL funiculus; facilitatory to FLEXORS
  • PONTINE: VENTRAL funiculus; facilitatory to EXTENSORS

(unclear if decussations)

MedulLary = Latera, fLexors

29
Q

2 subtypes of medullary reticulospinal tracts (King)

A
  • Medial: projects to SC
  • Lateral: inhibits medial tract
30
Q

2 VESTIBULOSPINAL TRACTS

A
  • Origin from 4 VN
  • Both ipsilateral
  • Both travel in VENTRAL funiculus
  • Both facilitatory to EXTENSORS
  • Lateral v.s.t.: limbs + axial muscles
  • Medial v.s.t: neck + shoulders
31
Q

OLIVARY NUCLEUS - role

A

Provides feedback loops from extrapyramidal system to cerebellum

32
Q

OLIVARY NUCLEUS - location

A

Dorsal to the pyramids (medulla)

33
Q

Describe loop from olivary nucleus to cerebellum (slide 56)

A

Cerebral cortex -> red nucleus -> olivary nucleus -> caudal cerebellar peduncle -> cerebellum -> rostral cerebellar peduncle, to either
- red nucleus
- back to cerebral cortex

34
Q

Describe two loops between extrapyramidal system and cerebellum

A
  1. Reticular formation (decussates) + vestibular nuclei (ipsilateral) –> caudal c.p. –> cerebellum –> caudal c.p.
  2. Tectum (decussates) –> rostral c.p. –> cerebellum –> rostral c.p.

Neuroanatomy (20 decks)

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