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501 Neuro > Motor Pathways > Flashcards

Motor Pathways Flashcards

1
Q

Brainstem internal anatomy: what is the white matter?

A

Composed mostly of axons in fasciculi, tracts, leminisci, and peduncles

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2
Q

What color does the white matter stain in a myelin stain?

A

Grey

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3
Q

The rostral and caudal midbrain contain the ____ pathway

A

Descending

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4
Q

What tracts do the rostral and caudal midbrain contain?

A

Corticospinal tract
Corticonuclear tract

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5
Q

What is the function of the corticospinal and corticonuclear tract?

A

Aid with voluntary movement

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6
Q

Where does the corticospinal tract lead to?

A

Axons run down to the spinal cord

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7
Q

Where does the corticonuclear tract lead to?

A

Axons travel down to nuclei, go down to brainstem

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8
Q

Brainstem internal anatomy: what is the grey matter?

A

Composed of cell bodies and dendrites in the posterior and anterior horns

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9
Q

What color does the grey matter stain in a myelin stain?

A

White

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10
Q

Features of the spinal cord cross-sections while going down?

A

Greatest diameter and largest horns at cervical and lumbosacral levels
White matter decreases from superior to inferior

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11
Q

The descending pathway goes through the …

A

Rostral midbrain, caudal midbrain, middle pons, caudal pons, rostral medulla, and caudal medulla

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12
Q

In the cervical spinal cord, the descending pathway becomes the

A

Lateral corticospinal tract

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13
Q

LMNs innervate …. originate at …. terminate at …..

A

Innervate: skeletal muscle
Originate: brainstem and spinal cord
Terminate: skeletal muscle

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14
Q

What are signs of LMN damage?

A

Flaccid paralysis (paralysis with hypotonia)
Hyporeflexia (reflexes diminished)
Atrophy of muscle after weeks or months
Fasciculations (twitches)

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15
Q

What does one motor unit consist of?

A

One LMN, all of the skeletal muscle fibers it innervates

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16
Q

Brainstem LMNs lead to ….

A

Muscles contracting

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17
Q

LMNs for head and neck muscles, cell bodies are located….. axons are located in ……

A

Cell bodies in brainstem nuclei or accessory nucleus of cervical spinal cord
Axons in cranial nerves

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18
Q

The cell bodies for LMNs for limb muscles are located in

A

Spinal cord anterior horn
C5 to T1 for upper limb
L2 to S4 for lower limb

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19
Q

Spinal cord LMNs: axons in the limb plexus and peripheral nerves innervate

A

Brachial plexus innervates upper limb
Lumbosacral plexus for lower limb

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20
Q

Spinal cord LMNs: axons from medial part of the anterior horn innervate

A

Proximal muscles

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21
Q

Spinal cord LMNs: axons from lateral part of the anterior horn innverate

A

Distal muscles

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22
Q

Most muscles receive innervation from _____ spinal cord levels

A

Multiple
Need damage at multiple levels for paralysis

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23
Q

The function of UMNs is to …..

A

Activate LMNs

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24
Q

UMNs originate at ….. and terminate at…..

A

Originate: cerebral cortex and brainstem
Terminate: brainstem and spinal cord

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25
Q

What are signs of UMN damage?

A

Spastic paralysis with hypertonia
Clonus (rapid series of rhythmic contractions)
Hyperreflexia
Positive Babinski signs (extend large during plantar felxor response)

26
Q

Where is the origin of the corticospinal system (pyramidal system)?

A

Medial and superior portion of precentral gyrus to spinal cord

27
Q

What is the course of the corticospinal system?

A

Corona radiata, posterior limb of internal capsule, cerebral crus, descending fibers in pons, pyramid, pyramidal decussation (crossing to contralateral side), lateral corticospinal tract

28
Q

Where does the corticospinal system terminate?

A

Contralateral spinal cord anterior horn
Area for precise and detailed movements

29
Q

What is the function of the corticospinal system?

A

Activate LMNs which innervate flexor muscles of upper and lower limbs
Important for distal flexor muscles of wrist and fingers)

30
Q

What part of the internal capsule is part of the corticospinal system?

A

Posterior limb
Contains axons from primary somatomotor cortex to spinal cord genu

31
Q

What are the vascular territories of the corticospinal system?

A

Spinal cord: anterior spinal artery
Medulla: anterior spinal artery
Pons: basilar artery
Midbrain: posterior cerebral artery

32
Q

Where is the origin of the corticonuclear system (corticobulbar system)?

A

Lateral portion of the precentral gyrus to brainstem and spinal cord

33
Q

What is the course of the corticonuclear system?

A

Corona radiata, genu of internal capsule, cerebral crus, descending fibers in pons

34
Q

Where is the termination of the corticonuclear system?

A

Contralateral projections to nuclei of CN X and XII
Ipsilateral projections to CN XI nucleus
Bilateral projections to CN V nucleus
No projection to nuclei of CN II, IV, and VI

35
Q

What is the function of the corticonuclear system?

A

Activate LMNs which control
V: mastication
VII: facial expression
X: swallowing and vocalization
Xi: shrugging shoulders and turning head to contralateral side
XII: tongue movements

36
Q

What are the targets of the corticonuclear system in the face and neck?

A

Facial motor nucleus CN VII: facial expression muscles
Nucleus ambiguus CN X: uvula, soft palate muscles, larynx
Hypoglossal nucleus CN XII: tongue muscles

37
Q

What is the primary UMN lesion sign for the corticonuclear system?

A

Contralateral spastic paralysis

38
Q

What are some clinical signs for lesions of the corticonuclear system?

A

Spastic paralysis of contralateral face (CN VII)
Uvula deviates contralateral to paralysis, dysarthria, difficulty swallowing, loss of gag reflex (CN X)
Tongue deviates to ipsilateral side of paralysis, dysarthria (weak or hoarse voice, slurred speech) (CN XII)

39
Q

What areas is the motor cortex influenced by?

A

Supplementary motor cortex
Premotor cortex

40
Q

Ordering of firing in the motor association cortex?

A
  1. Ready (supplementary motor cortex)
  2. Set (premotor cortex)
  3. Go (primary motor cortex)
41
Q

Damage in the motor association cortex leads to

A

Apraxia

42
Q

What is apraxia?

A

Inability to produce voluntary movement despite normal muscle power and tone and normal reflexes

43
Q

Review of blood supply of the cerebrum:
MCA supplies ….
ACA supplies ….
PCA supplies ….

A

MCA: lateral cerebral hemispheres
ACA: medial frontal and parietal lobes
PCA: medical temporal and occipital lobes

44
Q

UMNs activate …. originate …. terminate ….

A

Activate LMNs
Originate in the cerebral cortex and brainstem
Terminate in the spinal cord

45
Q

What is the sequence of events of a tendon (stretch) reflex?

A

Muscle is stretched
Muscle spindles excite sensory neurons
Sensory neurons excite LMNs to stretched muscles
LMNs stimulate stretched muscles to contract

46
Q

What are muscle spindles?

A

Located in skeletal muscles
Continuously monitor length and changes in the length of muscle

47
Q

What is the jaw jerk reflex?

A

Stretch reflex that is used to rest the status of UMNs that activate trigeminal motor nucleus
Mandible is tapped at a downward angle just below the lips at the chin while the mouth is held slightly open

48
Q

What would the jaw jerk reflex look like with UMN damage? What is the normal reflex?

A

Abnormal: Masseter will contract and jerk the mandible superiorly, exaggerated
Normal: reflex is light or absent

49
Q

The tendon reflex is used to … usually tested on …

A

Test integrity of spinal cord segments
Biceps, triceps, patellar, achilles

50
Q

Where is the origin of the vestibulospinal tract?

A

Vestibular nuclei

51
Q

What is the function of the vestibulospinal tract?

A

Activates ipsilateral spinal cord LMNs which innervates trunk and proximal limb and extensor muscles related to balance and posture

52
Q

What does the vestibulospinal tract activate in response to?

A

Postural instability
Feedback pathway
Vestibulospinal tract is activated to reestablish or maintain stable posture

53
Q

Where is the origin of the reticulospinal tract?

A

Reticular formation

54
Q

What is the function of the reticulospinal tract?

A

Activates ipsilateral spinal cord LMNs which innervate trunk and limb extensor muscles
Related to postural support of limb movements

55
Q

When is the reticulospinal tract activated …..

A

Prior to limb movement

56
Q

When is the reticulospinal tract activated …..

A

Prior to limb movement

57
Q

The feedforward pathway of the reticulospinal tract activates

A

The reticulospinal tract to establish appropriate posture to support limb movement

58
Q

LMNs connected to flexor muscles are activated by ______ tract

A

Corticospinal tract

59
Q

LMNs connected to extensor muscles are activated by ____ tract and ____ tract

A

Vestibulospinal tract
Reticulospinal tract

60
Q

UMN systems: corticospinal tract general functions

A

Neurons of motor cortex activate contralateral spinal cord LMNs
Control of individual muscles or groups of muscles for purposeful movement
Mainly flexor muscles, especially those related to dexterous movement

61
Q

UMN systems: corticonuclear tract general functions

A

Neurons of motor cortex activate the brainstem LMNs of cranial nerves
Does not activate LMNs associated with CN III, IV, and VI

62
Q

UMN systems: vestibulospinal tract general functions

A

Neurons of vestibular nuclei activate ipsilateral spinal cord LMNs
Control of trunk and proximal limb extensor muscles related to posture and balance in response to postural instability feedback pathway activating the vestibulospinal tract to reestablish or maintain posture

501 Neuro (16 decks)

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