Exam #2: Motor Systems I

Question 1

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

Answer 1

Motor cortex
Thalamus
Basal Ganglia 
Cerebellum 
Brain stem 
Spinal Cord

Question 2

Outline the general pathway that controls voluntary movement.

Answer 2

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

Question 3

What is the function of the motor cortex?

Answer 3

Planning & executing complex voluntary movement

Question 4

What are the cortical areas involved in motor activity?

Answer 4

1) Primary motor cortex

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

Question 5

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

Answer 5

1) Corticonuclear tract

2) Corticospinal tract

Question 6

Where does the corticonuclear tract terminate?

Answer 6

Most cranial nerve motor nuclei

Question 7

Where does the corticospinal tract terminate?

Answer 7

All spinal levels

Question 8

What side of the body does the corticospinal tract control?

Answer 8

Contralateral

Question 9

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

Answer 9

Frontal Lobe

• Primary Motor Cortex
• Premotor Cortical Areas

Parietal Lobe
- Posterior Parietal Cortex

Question 10

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

Answer 10

• Frontal lobe

- Planning of movement

Question 11

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

Answer 11

• 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

Question 12

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

Answer 12

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

Question 13

What Brodmann area does the SMA & PMC correspond to?

Answer 13

Brodmann 6

Question 14

What is the Frontal Eye Field (FEF)?

Answer 14

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

Brodmann 8

Question 15

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

Answer 15

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

Question 16

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

Answer 16

Same medial to lateral organization

• Lower leg & foot medial
• Hand & face distal

Question 17

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

Answer 17

Face & hand

Question 18

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

Answer 18

• Precentral gyrus (primary motor cortex)= Bordmann 4

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

Question 19

What are the areas of the brain that influence movement?

Answer 19

Somatosensory cortex

Question 20

Where does the postcentral gyrus synapse to influence movement?

Answer 20

Neurons of the sensory pathways

Question 21

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

Answer 21

Layer V

*These are pyramidal cells

Question 22

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

Answer 22

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

Question 23

Outline the corticospinal tract.

Answer 23

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

Question 24

Where does crossing over of the corticospinal tract occur?

Answer 24

Caudal Medulla

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

Question 25

Where do the anteror corticospinal tract axons cross-over?

Answer 25

At the level of their innervation in the spine

Question 26

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

Answer 26

Interneurons that then synapse with LMN

*Some synapse directly with LMN

Question 27

What are the crossing fibers called in the medulla?

Answer 27

Motor decussation (in the caudal medulla)

Question 28

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

Answer 28

Anterior white commissure

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

Question 29

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

Answer 29

Lateral= all level 
Anterior= C1- T6 only

Question 30

Where do ALL corticospinal tract neurons synapse?

Answer 30

Contralateral voluntary movement

Question 31

What muscles does the anterior corticospinal tract control?

Answer 31

Axial muscles of the shoulder and trunk

Question 32

What does the lateral corticospinal tract control?

Answer 32

Upper limb and lower limb muscles

Question 33

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

Answer 33

Ascending= get thicker as you go up

Descending= get smaller as you go down

Question 34

What are the signs of an upper motor neuron lesion?

Answer 34

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

Question 35

Describe the progression of spastic paralysis.

Answer 35

• 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)

Question 36

What is the Babinski Reflex?

Answer 36

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

Question 37

What are the signs of lower motor neuron lesion?

Answer 37

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)

Question 38

What will a lesion of the ACA cause?

Answer 38

Sensory & motor deficits of the contralateral leg/foot

Question 39

What will a lesion of the MCA cause?

Answer 39

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

Question 40

What will occlusion of the lenticulostriate arteries effect?

Answer 40

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

Question 41

What part of the brain is supplied by the PCA?

Answer 41

Midbrain, specifically in the basis pedunculi/ crus cerebri

Question 42

What artery supplies the corticospinal tract in the pons?

Answer 42

Basilar/pontine arteries

Question 43

What does the anterior spinal artery supply

Answer 43

• Anterior corticospinal tract
• Lateral corticospinal tract
• Spinothalamic tracts

Question 44

What does the posterior spinal artery supply?

Answer 44

DC/ML