Tracts & Motor Control

Question 1

Name the levels of the hierarchy of motor control

Answer 1

1. Basal ganglia and cortical association areas
2. cerebellum & motor cortex
3. brainstem & spinal cord

Question 2

what is the function of the basal ganglia & cortical association areas in motor control?

Answer 2

gather visual, auditory, proprioceptive, etc. info about relative position of the body, object, and overall intention of movement

Question 3

what is the function of the cerebellum & motor cortex in motor control?

Answer 3

plan the sequence and timing of muscle contraction & relaxation to ensure smooth movement

Question 4

what is the function of the brainstem & spinal cord in motor control?

Answer 4

execute movement

Question 5

what structures form the motor cortex?

Answer 5

• primary motor cortex (area 4, precentral gyrus)
• premotor & supplementary motor cortices (area 6)

Question 6

what are the 2 major descending pathways?

Answer 6

lateral pathway
(ventro)medial pathway

Question 7

descending tracts send information about… to…

Answer 7

execution of movement to LMNs in spinal cord

Question 8

the lateral pathway influences motor neurons that innervate…

Answer 8

distal muscles of the limbs

Question 9

what tracts make up the lateral pathway?

Answer 9

• lateral corticospinal tract
• rubrospinal tract

Question 10

the ventromedial pathway influences motor neurons that innervate…

Answer 10

axial & proximal limb muscles

Question 11

what tracts make up the ventromedial pathway?

Answer 11

• ventral corticospinal tract (core mm)
• pontine & medullary reticulospinal tract
• vestibulospinal tract
• tectospinal tract

Question 12

where does the corticospinal tract begin?

Answer 12

motor cortex (4,6) and somatosensory cortex

Question 13

describe the path of the corticospinal tract

Answer 13

• motor cortex & somatosensory cortex
• corona radiata
• post. limb of internal capsule
• crus cerebri
• basilar pons
• pyramid
• pyramidal decussation (85%)
• LCST
• v. horn cells @ every level
  -> distal primarily flexor mm.

Question 14

where does the rubrospinal tract begin?

Answer 14

red nucleus (under control of the cortex)

Question 15

where does the rubrospinal tract cross?

Answer 15

pons

Question 16

where does the rubrospinal tract terminate and innervate?

Answer 16

ventral horn cells, especially in cervical spine -> innervates distal primarily flexor mm.

Question 17

symptoms of lateral pathway injury

Answer 17

• paresis/paralysis (weakness), no atrophy
• spasticity/hypertonia/hyperreflexia (UMN)
• clasp knife rigidity
• babinski sign
• absent superficial reflexes

Question 18

pontine reticulospinal tract

Answer 18

• reticular formation (pons)
• v. horn cells
  -> facilitation of antigravity mm. (i.e., extensors of lower limb)

Question 19

medullary reticulospinal tract

Answer 19

• reticular formation (medulla)
• v. horn cells
  -> inhibit antigravity mm.

Question 20

vestibulospinal tract runs from the ____ nuclei to ____ bilaterally

Answer 20

vestibular nuc.
v. horn cells

Question 21

vestibulospinal tract functions

Answer 21

• control head & back muscles based on directional info
• upper & lower limb extension

Question 22

vestibulospinal tract muscle control is based on…

Answer 22

directional info it receives from vestibular apparatus in inner ear

Question 23

where does the tectospinal tract begin?

Answer 23

superior colliculus
(receives retinal input)

Question 24

where does the tectospinal tract decussate?

Answer 24

medulla

Question 25

where does the tectospinal tract end?

Answer 25

v. horn cells

Question 26

the tectospinal tract facilitates…

Answer 26

orientation of head & eyes to stimulus

Question 27

lesion of the brainstem above the vestibular nuclei

Answer 27

• eliminates corticospinal & rubrospinal tracts
• decerebrate rigidity - tonic extension

Question 28

lesion of cerebral hemispheres with intact brainstem

Answer 28

• eliminates corticospinal, spares rubrospinal
• decorticate rigidity: tonic legs extension with arm flexion

Question 29

explain decorticate rigidity

Answer 29

tonic leg extension + arm flexion:
- red nuc (rubrospinal) projects more to cervical area of spinal cord and counteracts vestibular facilitation (ext) in arms only

Question 30

what tract is responsible for knee extension when there is UMN injury?

Answer 30

vestibulospinal tract

Question 31

what tract is responsible for triple flexion of the upper limb when the corticospinal tract is injured?

Answer 31

rubrospinal tract

Question 32

roots of the brachial plexus are ____ rami

Answer 32

ventral

Question 33

if a ventral root is lesioned, what is the expected effect?

Answer 33

all muscles with any innervation from that spinal level are impacted, but muscles with major innervation will lose motor function

Question 34

if the spinal nerve is lesioned, what is the expected effect?

Answer 34

both sensory and motor are affected

Question 35

if a dorsal ramus is lesioned, what is the expected effect?

Answer 35

loss of sensory & motor to back

Question 36

if a ventral ramus is lesioned, what is the expected effect?

Answer 36

loss of sensory & motor to front & extremities

Question 37

a lesion of the ventro-medial aspect of the ventral horn in the cerval spine affecting axial extensor muscles is an example of ____

Answer 37

somatotopic organization of ventral horn cell bodies