Exam #2: Motor Systems I Flashcards

1
Q

What are the different parts of the nervous system that orchestrate motor function?

A
Motor cortex
Thalamus
Basal Ganglia 
Cerebellum 
Brain stem 
Spinal Cord
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2
Q

Outline the general pathway that controls voluntary movement.

A

1) Association cortex– desire
2) Premotor cortical areas–plan
3) Primary motor cortex–execution

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3
Q

What is the function of the motor cortex?

A

Planning & executing complex voluntary movement

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4
Q

What are the cortical areas involved in motor activity?

A

1) Primary motor cortex

2) Premotor cortical areas (previously called secondary motor cortex)

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5
Q

What are the two main tracts that are involved in pathways of conscious, voluntary motor control?

A

1) Corticonuclear tract

2) Corticospinal tract

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6
Q

Where does the corticonuclear tract terminate?

A

Most cranial nerve motor nuclei

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7
Q

Where does the corticospinal tract terminate?

A

All spinal levels

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8
Q

What side of the body does the corticospinal tract control?

A

Contralateral

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9
Q

What cortical areas involved in the production of movement are located in the frontal lobe? What areas are located in the parietal lobe?

A

Frontal Lobe

  • Primary Motor Cortex
  • Premotor Cortical Areas

Parietal Lobe
- Posterior Parietal Cortex

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10
Q

What is the general function of the premotor cortical areas? Where are the premotor cortical areas located?

A
  • Frontal lobe

- Planning of movement

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11
Q

What is the function of the primary motor cortex? Where is the primary motor cortex located?

A
  • Frontal lobe (pre-central gyrus)
  • Receives the plan from the premotor cortical areas and executes the movement

*Note that this area is also referred to as Brodmann’s area 4

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12
Q

What is the supplementary motor area (SMA)?What is the premotor cortex (PMC)? What is their function?

A

These are BOTH part of the premotor cortical areas that plan movement
- Specifically, they orient the trunk & proximal limb musculature in the direction of intended movement

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13
Q

What Brodmann area does the SMA & PMC correspond to?

A

Brodmann 6

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14
Q

What is the Frontal Eye Field (FEF)?

A

Contains neurons that send axons down to the cranial motor nerve nuclei in the brainstem that are involved in eye movement

Brodmann 8

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15
Q

What is the Posterior Parietal Cortex (PMA)? What is the function?

A

This is a region in the posterior parietal cortex that is involved in visual guidance of movement

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16
Q

How does the orientation of the motor homunculus compare to the sensory homunculus?

A

Same medial to lateral organization

  • Lower leg & foot medial
  • Hand & face distal
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17
Q

What parts of the body have the most cortex dedicated to it?

A

Face & hand

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18
Q

What area does the Precentral gyrus correspond to? What bout the Postcentral gyrus?

A
  • Precentral gyrus (primary motor cortex)= Bordmann 4

- Postcentral gyrus (primary sensory cortex) = Brodmann 3, 1, & 2

19
Q

What are the areas of the brain that influence movement?

A

Somatosensory cortex

20
Q

Where does the postcentral gyrus synapse to influence movement?

A

Neurons of the sensory pathways

21
Q

What layer of the cortex are the upper motor neurons located in?

A

Layer V

*These are pyramidal cells

22
Q

What is the difference between an upper and lower motor neuron?

A
Lower= nerve that innervates a skeletal muscle 
Upper= nerves that synapse prior to the nerve that projects to skeletal muscle
23
Q

Outline the corticospinal tract.

A

1) Cortex Layer 5
2) Corona Radiata
3) Internal capsule
4) Midbrain–Crus Cerebri
5) Basal pons
6) Medulla–Pyramid
7) Spinal cord

24
Q

Where does crossing over of the corticospinal tract occur?

A

Caudal Medulla

*****Note, ~85% of the nerves decussate to form the lateral corticospinal tract; those that don’t become the anterior corticospinal tract

25
Q

Where do the anteror corticospinal tract axons cross-over?

A

At the level of their innervation in the spine

26
Q

What do most of the UMN in the spinal cord syapse with?

A

Interneurons that then synapse with LMN

*Some synapse directly with LMN

27
Q

What are the crossing fibers called in the medulla?

A

Motor decussation (in the caudal medulla)

28
Q

Where does the anterior corticospinal tract decussate? What else decussates here?

A

Anterior white commissure

*****Note that the spinothalamic tract also decussates here

29
Q

What is the difference between the Anterior & lateral corticospinal tracts?

A
Lateral= all level 
Anterior= C1- T6 only
30
Q

Where do ALL corticospinal tract neurons synapse?

A

Contralateral voluntary movement

31
Q

What muscles does the anterior corticospinal tract control?

A

Axial muscles of the shoulder and trunk

32
Q

What does the lateral corticospinal tract control?

A

Upper limb and lower limb muscles

33
Q

Review how the morphology of the spinal cord changes with ascending & descending tracts.

A

Ascending= get thicker as you go up

Descending= get smaller as you go down

34
Q

What are the signs of an upper motor neuron lesion?

A

1) Spastic paralysis
2) Hyperreflexia
3) Mild muscle atrophy
4) Babinski’s Sign

35
Q

Describe the progression of spastic paralysis.

A
  • Temporary paresis, flaccid paralysis, hypotonia, & hyporeflexia
  • Regain proximal function after roughly 2x weeks
  • Hypotonia converts to Hypertonicity

**Inhibitor reflexes from basal ganglia are blocked, causing hypertonia (uninhibited gamma fibers)

36
Q

What is the Babinski Reflex?

A

Fanning & dorsiflexion of the great toe is caused by:

Called the extensor plantar response
- Normal in the newborn b/c descending motor axons are NOT myelinated

37
Q

What are the signs of lower motor neuron lesion?

A

1) Decrease in muscle strength
2) Hypotonia
3) Hyporeflexia
4) Flaccid paralysis
5) Severe muscle atrophy
6) Fibrillations (1 fiber)
7) Fasiculations (gross muscle twitch)

38
Q

What will a lesion of the ACA cause?

A

Sensory & motor deficits of the contralateral leg/foot

39
Q

What will a lesion of the MCA cause?

A

Sensory & motor deficits in the contralateral trunk/UL/ face

40
Q

What will occlusion of the lenticulostriate arteries effect?

A

Lenticulostriate= deep branches of the MCA to the internal capsule that will effect:

  • DC-ML (VPL thalamus)
  • Spinothalamic (Intralaminar)
  • Corticospinal tract

**Lesion will cause contralateral motor & sensory deficits

41
Q

What part of the brain is supplied by the PCA?

A

Midbrain, specifically in the basis pedunculi/ crus cerebri

42
Q

What artery supplies the corticospinal tract in the pons?

A

Basilar/pontine arteries

43
Q

What does the anterior spinal artery supply

A
  • Anterior corticospinal tract
  • Lateral corticospinal tract
  • Spinothalamic tracts
44
Q

What does the posterior spinal artery supply?

A

DC/ML