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VET 404: Neurology > Motor Systems: UMNs > Flashcards

Motor Systems: UMNs Flashcards

1
Q

are upper motor neurons part of CNS or PNS

A

CNS only
brain –> spinal cord

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2
Q

function of UMNs

A

inhibit lower motor neurons:

initiate the process of voluntary movement
maintain muscle tone
regulate posture

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3
Q

UMN systems

A
  1. pyramidal
  2. extrapyramidal
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4
Q

where are neurons of pyramidal system located

A

cell bodies: primary motor cortex
axons: brainstem and spinal cord

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5
Q

pyramidal pathways

A
  1. corticospinal tract
  2. corticonuclear tract
  3. corticopontocerebellar tract
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6
Q

corticospinal tract pathway

A

cortex –> internal capsule –> axons through corticospinal tract –> splits into lateral and ventral

lateral: decussates at junction of brainstem and spinal cord –> synapses on LMNs in spinal cord

ventral: continues ipsilateral to synapse on LMNs in spinal cord

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7
Q

what do corticospinal tract neurons innervate

A

synapses with LMNs that innervate skeletal muscle of trunk, limbs, and tail

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8
Q

function of corticospinal tract

A

facilitate contralateral flexors
inhibit contralateral extensors

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9
Q

corticonuclear tract pathway

A

cortex –> internal capsule –> axons through corticonuclear tract –> decussates at different level of brainstem –> terminates at cranial nerve nuclei

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10
Q

what do corticonuclear tract neurons innervate

A

synapses with LMNs that innervate cranial nerves

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11
Q

function of corticonuclear tract

A

eye movement (CN III, IV)
mastication (CN V)
facial expression (CN VII)
neck movement (CN XI)
tongue movement (CN XII)

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12
Q

corticopontocerebellar tract pathway

A

cortex –> pons –> cerebellum

corticopontine tract: cortex –> pontine nuclei

pontocerebellar tract: pontine nuclei –> decussates –> cerebellum

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13
Q

function of corticopontocerebellar tract

A

feedback pathway from cortex to cerebellum to allow cerebellum to plan movements

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14
Q

signs of pyramidal tract lesions

A

loss of skilled voluntary movement
- contralateral postural reaction deficits

NORMAL gait - NO paresis/paralysis

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15
Q

extrapyramidal systems

A
  1. basal nuclei
  2. substantia nigra
  3. rubrospinal tract
  4. reticular formation
  5. vestibulospinal tracts
  6. tectospinal tracts
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16
Q

basal nuclei

A

subcortical nuclei in each cerebral hemisphere

caudate nuclei
putamen
globus pallidus
claustrum

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17
Q

function of basal nuclei

A

modulation of motor activity from the motor cortex

goes through the thalamus

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18
Q

direct pathway of basal nuclei function

A

facilitates execution of motor command

  1. caudate/putamen inhibit medial globus pallidus
  2. medial globus pallidus can’t inhibit thalamus
  3. thalamus excites cerebral cortex
  4. executes motor function
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19
Q

indirect pathway of basal nuclei

A

inhibits execution of motor command

  1. caudate/putamen inhibit lateral globus pallidus
  2. later globus pallidus can’t inhibit subthalamic nuclei
  3. subthalamic nuclei excites medial globus pallidus
  4. medial globus pallidus inhibits thalamus
  5. thalamus can’t excite cerebral cortex
  6. no execution of motor function
20
Q

signs of basal nuclei dysfunction

A

young animals normal until 4 months old
- lack of movement initiation
- festination

21
Q

yellow star thistle toxicity

A

necrosis of global pallidus and substantia nigra

22
Q

substanstia nigra

A

midbrain nucleus involving dopaminergic neurons

23
Q

function of substantia nigra

A

synapses onto dopamine receptors in caudate and putamen to INCREASE thalamic excitation of motor cortex
- facilitates D1 receptors
- inhibits D2 receptors

24
Q

D1 receptors

A

located in medial caudate and putamen; ACTIVATED by substantia nigra

activates direct pathway –> facilitates motor execution

25
Q

D2 receptors

A

located in lateral caudate and putamen; INHIBITED by substantia nigra

activates indirect pathway –> inhibits motor execution

26
Q

rubrospinal tract

A

tracts the extend to and from the midbrain red nucleus

27
Q

function of the rubrospinal tract

A

facilitates flexors
inhibits extensors

28
Q

red nucleus

A

located in midbrain near midline reticular formation

  • receives inputs from cortex, basal nuclei, cerebellum
  • send outputs from midbrain –> pons –> medulla –> spinal cord
29
Q

olivocerebellar tract pathway

A

rubrospinal tract –> olivary nucleus in medulla –> decussates to contralateral cerebellum

30
Q

olivocerebellary tract function

A

monitors extrapyramidal systems
lesions cause loss of coordination

31
Q

reticular formation

A

meshwork of nuclei throughout the brainstem

  1. pontine reticulospinal tract
  2. medullary reticulospinal tract
32
Q

function of reticular formation

A

posture and locomotion
tracts are used to balance facilitation and inhibition of LMNs

33
Q

pontine reticulospinal tract function

A

facilitates extensors
inhibits flexors

34
Q

pontine reticulospinal tract pathway

A

pontine reticular formation (pons) –> ipsilateral ventral funiculus –> spinal cord

35
Q

medullary reticulospinal tract function

A

facilitates flexors
inhibits extensors

36
Q

medullary reticulospinal tract pathway

A

medullary reticular formation (medulla) –> ipsilateral ventral funiculus –> spinal cord

37
Q

vestibulospinal tracts

A

tracts that extend from vestibular nuclei to spinal cord

  1. medial vestibulospinal tract
  2. lateral vestibulospinal tract
38
Q

function of vestibulospinal tracts

A

maintain balance of body against gravity

facilitates extensors
inhibits flexors

39
Q

medial vestibulospinal tract

A

maintains head position by synapsing on neck/shoulder muscle LMNs

medial vestibulospinal nuclei –> ipsilateral ventral funiculus –> spinal cord

40
Q

lateral vestibulospinal tract

A

stabilizes body posture by synapsing on trunk/limb muscle LMNs

lateral vestibulospinal nuclei –> ipsilateral ventral funiculus –> spinal cord

41
Q

tectospinal tract

A

tracts extending from colliculi to spinal cord

42
Q

function of tectospinal tract

A

turns head toward visual or auditory stimuli

facilitates extensors of cervical LMNs

43
Q

tectospinal tract pathway

A

rostral/caudal colliculi –> decussates to contralateral ventral funiculus –> spinal cord

44
Q

most significant UMN lesion

A

medullary reticulospinal tract

signs: excessive extensor tone

45
Q

signs of extrapyramidal lesions

A

loss of voluntary movement

gait: paresis, delayed/absent protraction, spasticity (stiff gait)
posture: decerebrate rigidity, opisthotonus
mentation: comatose
reflexes: hyperreflexia, cross extensor reflex in lateral recumbency

VET 404: Neurology (23 decks)

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