Descending Motor Systems Flashcards
Function of descending motor systems
Control motor neurons
Autonomic function
Modifying sensory transmission
Control motor neuron excitability (gamma loop)
2 major classifications of the descending motor system
Medial motor system
Lateral motor system
5 Tracts in Medial Motor System
- Tectospinal Tract
- Medial vestibulospinal tract
- Lateral vestibulospinal tract
- Mediane\pontine reticulospinal tract
- Lateral\medullary reticulospinal tract
Which 3 pathways of the medial motor system are associated with MLF
Tectospinal tract
Medial vestibulospinal tract
Medial\pontine reticulospinal tract
Key characteristics of all Medial Motor System tracts
- Terminate bilaterally
- Control neck & trunk movements
- Enter anterior funiculus of spinal cord
- Terminate only in the cervical & upper thoracic spinal cord (MLF)
Tectospinal tract
Reflex hand & arm movement in response to visual & auditory stimuli
Medial vestibulospinal tract
Reflex adjustment of head position in response to vestibular stimuli
Medial\pontine reticulospinal tract
Allows head movement to follow eye movement
Lateral vestibular spinal cord
Excites ipsilateral extensor motor neurons
Lateral reticulospinal tract
Gross movements and regulates muscle tone
Controlled by corticobulbar tract
2 tracts in the Lateral Motor System
- Rubrospinal tract
2. Corticospinal tract
Lateral motor neurons terminate on
lateral part of intermediate gray & motor neurons
Rubrospinal Tract
Descending autonomic fibers
Respiratory control
Generalized gross movements
Regulates gamma neurons
Corticospinal tract
Voluntary movement from the cortex
Regulate sensory information
Fast and highly skilled movement
Corticospinal tract pathway
PIC-BMS-LF Precentral Gyrus Internal capsule (posterior limb) Cerebral peduncle Basal pons Medullary pyramids Decussate in the spinal cord (90%) Lateral funiculus
10 % of the cortical spinal cord fibers do not decussate, where do they synapse
Dorsal horn of spinal cord
Interneurons that control independent digits
Originates from which nucleus
Tectospinal tract
Superior colliculus
Originates from which nucleus
Medial vestibulospinal tract
Medial vestibular nucleus
Originates from which nucleus
Pontine reticulospinal tract
PPRF
Paramedian pontine reticulospinal tract
Originates from which nucleus
Lateral vestibulospinal nucleus
Lateral vestibular nucleus
Originates from which nucleus
Lateral reticulospinal tract
Medulla
Originates from which nucleus
Rubrospinal tract
Red nucleus in the midbrain
Indirect corticospinal tract
3 functions
- Allows cortex to control descending motor tracts that do not originate from the cortex i.e.red nucleus and superior colliculus
- Muscle tone
- Body stabalization
Anticipatory maintenance of body posture before a movement is associated with
Indirect corticospinal tract
Inhibits spinal cord reflexes
Cortico-reticulo-spinal pathway
Corticobulbar Tracts
Inhibitory tracts between cortex and the brainstem
Can be used as an indirect corticospinal pathway
Unilateral lesions of the upper motor neuron branches of CN VII (facial) result in
Unilateral paralysis on the contralateral side
Unilateral lesions of CN VII branches innervating the upper face result in
No clinical weakness
These neurons terminate bilaterally
Unilateral lesions of motor neuron branches of CN VII innervating lower face result in
Contralateral paralysis
The neurons terminate with decussation
Unilateral lesions to the facial nerve prior to branching result in
Ipsilateral paralysis
Where in the cortex is movement initiated
Premotor cortex
Which part of the cortex is only activated if movement occurs
Primary motor cortex
Which area of the cortex is active during rehearsal or preparation of movement
Premotor cortex\supplementary motor area
