Tracts & Motor Control Flashcards
Name the levels of the hierarchy of motor control
- Basal ganglia and cortical association areas
- cerebellum & motor cortex
- brainstem & spinal cord
what is the function of the basal ganglia & cortical association areas in motor control?
gather visual, auditory, proprioceptive, etc. info about relative position of the body, object, and overall intention of movement
what is the function of the cerebellum & motor cortex in motor control?
plan the sequence and timing of muscle contraction & relaxation to ensure smooth movement
what is the function of the brainstem & spinal cord in motor control?
execute movement
what structures form the motor cortex?
- primary motor cortex (area 4, precentral gyrus)
- premotor & supplementary motor cortices (area 6)
what are the 2 major descending pathways?
lateral pathway
(ventro)medial pathway
descending tracts send information about… to…
execution of movement to LMNs in spinal cord
the lateral pathway influences motor neurons that innervate…
distal muscles of the limbs
what tracts make up the lateral pathway?
- lateral corticospinal tract
- rubrospinal tract
the ventromedial pathway influences motor neurons that innervate…
axial & proximal limb muscles
what tracts make up the ventromedial pathway?
- ventral corticospinal tract (core mm)
- pontine & medullary reticulospinal tract
- vestibulospinal tract
- tectospinal tract
where does the corticospinal tract begin?
motor cortex (4,6) and somatosensory cortex
describe the path of the corticospinal tract
- 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.
where does the rubrospinal tract begin?
red nucleus (under control of the cortex)
where does the rubrospinal tract cross?
pons
where does the rubrospinal tract terminate and innervate?
ventral horn cells, especially in cervical spine -> innervates distal primarily flexor mm.
symptoms of lateral pathway injury
- paresis/paralysis (weakness), no atrophy
- spasticity/hypertonia/hyperreflexia (UMN)
- clasp knife rigidity
- babinski sign
- absent superficial reflexes
pontine reticulospinal tract
- reticular formation (pons)
- v. horn cells
-> facilitation of antigravity mm. (i.e., extensors of lower limb)
medullary reticulospinal tract
- reticular formation (medulla)
- v. horn cells
-> inhibit antigravity mm.
vestibulospinal tract runs from the ____ nuclei to ____ bilaterally
vestibular nuc.
v. horn cells
vestibulospinal tract functions
- control head & back muscles based on directional info
- upper & lower limb extension
vestibulospinal tract muscle control is based on…
directional info it receives from vestibular apparatus in inner ear
where does the tectospinal tract begin?
superior colliculus
(receives retinal input)
where does the tectospinal tract decussate?
medulla
where does the tectospinal tract end?
v. horn cells
the tectospinal tract facilitates…
orientation of head & eyes to stimulus
lesion of the brainstem above the vestibular nuclei
- eliminates corticospinal & rubrospinal tracts
- decerebrate rigidity - tonic extension
lesion of cerebral hemispheres with intact brainstem
- eliminates corticospinal, spares rubrospinal
- decorticate rigidity: tonic legs extension with arm flexion
explain decorticate rigidity
tonic leg extension + arm flexion:
- red nuc (rubrospinal) projects more to cervical area of spinal cord and counteracts vestibular facilitation (ext) in arms only
what tract is responsible for knee extension when there is UMN injury?
vestibulospinal tract
what tract is responsible for triple flexion of the upper limb when the corticospinal tract is injured?
rubrospinal tract
roots of the brachial plexus are ____ rami
ventral
if a ventral root is lesioned, what is the expected effect?
all muscles with any innervation from that spinal level are impacted, but muscles with major innervation will lose motor function
if the spinal nerve is lesioned, what is the expected effect?
both sensory and motor are affected
if a dorsal ramus is lesioned, what is the expected effect?
loss of sensory & motor to back
if a ventral ramus is lesioned, what is the expected effect?
loss of sensory & motor to front & extremities
a lesion of the ventro-medial aspect of the ventral horn in the cerval spine affecting axial extensor muscles is an example of ____
somatotopic organization of ventral horn cell bodies
