Week 6: Descending Tracts, Reflexes, & Movement Flashcards
What is a UMN?
Starts & ends in the CNS
What is a LMN?
aka AMN; Synapses w/peripheral nerve
What is feed forward?
Anticipatory use of sensory info to prepare for movement (Used to create a motor program)
What is feedback?
Use of sensory info during/after movement to make corrections (Alters the motor program)
What is movement decomposition?
Segmented movement from a single jt rather than coordinated movement for multiple jt’s
What are 3 things that influence automatic movement routines?
Visual Input, Somatosensory Input, & Proprioceptive Input
Loss of visual, somatosensory, or proprioceptive input can cause what?
Some degree of movement decomposition
* Loss of accuracy * Timing issues * Loss of smoothness/efficiency * Can cause the need for conscious control
Other things that effect motor programs
- Intact NS/NS that needs to heal
- Skeletal muscle integrity & strength
- CV system
- Experience w/task
- Presence of well-learned movement patterns that need to be replaced
- Motivation (Conscious & unconscious)
Which tracts are for postural/gross movement tracts?
- Tectospinal
- Medial Reticulospinal
- Medial Corticospinal
- Medial Vestibulospinal
- Lateral Vestibulospinal
Where are the nuclei of postural/gross movement tracts located?
Medial spinal cord
What tracts are for fine movement & flexion?
- Lateral Corticospinal
- Lateral Reticulospinal
- Rubrospinal
Where are the nuclei of fine movement & flexion tracts located?
Lateral spinal cord
Examples of CPG’s
Walking, Running, Unicycling
CPG
Spinal cord circuitry that generates rhythmic, coordinated, & alternating movements w/minimal cortical input.
Results of UMN damage:
- Paresis/Paralysis
- Loss of fractionation
- Abn reflexes
- Velocity-dependent hypotonia
- Abn co-contractions–>Spastic CP
- Abn synergies
Results of LMN damage:
- Flaccid paralysis
- Atrophy
- Loss of reflexes
- Fibrillations
After a pt has a CVA, what side will they have motor & sensory loss?
Contralateral to the lesion
Sx’s of ALS
- Paresis
- Hyper-reflexia
- Babinski Sign
- Atrophy
- Fasciculations
- Difficulty swallowing, breathing, & speaking bc of CN involvement
Where does ALS cause destruction?
UMN’s, brainstem, & LMN’s
Brown-Sequard Syndrome
Injury to a hemisection of the SC
Sx’s of Brown-Sequard Syndrome
- Ipsilateral spastic paralysis below level of lesion
- Ipsilateral disruption of tactile, vibration, & position sense
- Contralateral destruction of pain & temp 1-2 levels below lesion
Sx’s of Brown-Sequard Syndrome
- Ipsilateral spastic paralysis below level of lesion
- Ipsilateral disruption of tactile, vibration, & position sense
- Contralateral destruction of pain & temp 1-2 levels below lesion
Explain crossed extension
Opposite side of the body doing opposite motions as a reflex
Explain reciprocal inhibition
Inhibitory neurons to an antagonist muscle
*Achieved by interneurons in the spinal cord linking LMN’s into fxnl groups
What is the fxn of the ventral anterior & lateral nuclei?
Motor planning & coordination
What is the fxn of the VPL?
Body sensation, pain, & temp
What is the fxn of the VPM?
Facial sensation, pain, temp, & taste
What is the fxn of the medial geniculate body?
Sound localization & perception
What is the fxn of the lateral geniculate body?
Coordination of visual signals
What is the fxn of the anterior, dorsal medial, & dorsal lateral nuclei?
Limbic system
What is the fxn of lateral posterior nuclei?
Sensory integration
What is the fxn of the pulvinar nuclei?
Sensory integration; Possibly visual attention
Interlamina Nuclei
Located in the Y of the intermedullary lamina
- Centromedian Nuclei
- Parafascicular Nuclei
What is the fxn of the centromedian nuclei?
Arousal & attention
What is the fxn of parafascicular nuclei?
Damage is linked to epilepsy
What tracts would be compromised if a pt had damage to their posterior spinal arteries?
Medial Lemniscal
What tracts would be compromised if a pt had damage to their anterior spinal arteries?
Damage to all other ascending tracts & all descending tracts
Fxn of medial vestibulospinal tract
Controls neck & upper back muscles bilaterally
*Receives info about head movement & position from the vestibular apparatus in the inner ear
Route of medial vestibulospinal tract
UMN) Starts in open medulla at the level of the 4th ventricle
- Splits & descends bilaterally
- Synapses in cervical & thoracic ventral gray horn
LMN) Goes to neck & upper back muscles
Fxn of lateral vestibulospinal tract
Helps maintain CoG over BoS when upright
- Responds to gravity info from the vestibular apparatus
- Facilitates extension
Route of lateral vestibulospinal tract
UMN) Starts in open medulla
- Descends ipsilaterally
- Synapses in ventral gray horns of T- & L-spine
LMN) Goes to midback, low back, thigh, & calf
What is the only postural/gross movement tract to decussate?
Tectospinal Tract
Fxn of medial corticospinal tract
Innervates neck, shoulder, & trunk muscles
Route of medial corticospinal tract
UMN) Starts in the cortex
- Travels through the internal capsule & anterior brainstem
- Descends through the ipsilateral, contralateral, & bilateral spinal cord in the ventral column
- Synapses in the gray horn at cervical & thoracic levels w/interneurons & AMN’s
LMn) Goes to neck, shoulder, & axial muscles
True or False: Muscles that contract bilaterally receive bilateral input from the cortex via the medial corticospinal tract
True
Fxn of the tectospinal tract
- Assists in head turning to coordinate w/visual & auditory stimuli
- Postural & gross movement (Cervical/head control)
Route of the tectospinal tract
UMN) Originates in the superior colliculus
- Decussates at the level of superior colliculus (midbrain)
- Descends in the contralateral ventral column
- Synapses in ventral gray horn in cervical levels
LMN) Goes to C-spine
*Traps & SCM
*Fun Fact: Synapses w/LMN in the same location as the corticobulbar tract
Fxn of lateral corticospinal tract
Controls voluntary movement & innervates limbs contralaterally
*Fractionates movement by activating inhibitory neurons to prevent unwanted muscles from contracting
Route of the lateral corticospinal tract
UMN) Starts in the motor planning areas of the primary motor cortex, premotor cortex, & supplmentary motor cortex (Think Homunculus!)
- Travels through the internal capsule, to the peduncles & anterior pons
- Decussates in the pyramids at the level of the medulla
- Travels in the lateral column
- Synapses in the ventral gray horn at cervical & lumbar levels
LMN) Goes to the muscle of the limbs
*Some fibers decussate again in the spinal cord
Fxn of rubrospinal tract
Assists w/movement control
Route of rubrospinal tract
UMN) Starts in red nucleus at the level of the peduncles
- Decussates at the level of the peduncles
- Descends in the lateral brainstem tegmentum & lateral column of the spinal cord w/the lateral corticospinal tract
- Synapses in ventral gray horn in cervical & thoracic levels
LMN) Goes to muscles that extend the wrist & fingers
Fxn of lateral reticulospinal tract
Facilitates flexors & inhibits extensors; Does the opposite during amb
Route of the lateral reticulospinal tract
UMN) Starts in the lateral reticular formation
- Descends in the anterior lateral funiculus
- Synapses in anterolateral gray horn
Fxn of corticobulbar tract
Innervates motor cranial nerves for face, tongue, throat, neck, & shoulders
Route of corticobulbar tract
UMN) Originates in the pre- & primary motor cortex
- Decussates before inferior colliculi (Neck in closed medulla)
- Synapses in different locations depending on the fiber’s final destination:
- Face (CN 5 & 7)=MLF at the level of the pons
- Tongue (CN12)=MLF of open medulla
- Neck (CN 11)=Ventral gray horn of C-spine
LMN) Becomes:
* CN5 to jaw * CN7 to eyes & lips * CN11 to neck * CN12 to tongue
Explain simple reflex arcs
- Have minimal descending input
* Stim afferent–>efferent–>ascending for cortical awareness
Explain reciprocal reflex patterns
Stim afferent–>efferent + reciprocal innervation of contralateral antagonist–>ascending for cortical awareness
True or False: CPG’s are under subcortical control
True
Paresis
Partial loss of voluntary motor control
Hemiparesis
Partial loss of voluntary motor control on one side of the body
Paralysis
Complete loss of voluntary motor control
Spasticity/Hypertonia
Velocity dependent incr in stretch reflex w/incr resting muscle tone
Rigidity
Resistance to passive stretch regardless of speed of force
Decerebrate Rigidity
UE & LE extension bc of midbrain damage
Decorticate Rigidity
UE flexion & LE extension bc of damage above the midbrain
Hypotonia
Low tone due to pervasive brain damage, genetic disorders, or developmental delays
What part of the nervous system does the polio virus attack?
AMN
True or False: CPG’s are linked contralaterally between extremities
True
Name the thalamic nuclei
- Ventral Anterior & Lateral
- VPL & VPM
- Medial & lateral geniculate bodies
- Anterior, Dorsal Medial, & Dorsal Lateral
- Lateral Posterior
- Pulvinar
Give an example of the crossed extension response
*
How does the CPG trigger a stepping response?
*
Which ascending tracts travel through the VPL of the thalamus?
Spinothalamic & Medial Lemniscal Tracts
What would be affected by unilateral damage to the corticospinal tract at the level of the medullary pyramids?
*
A pt presents w/L sided weakness+proprioceptive loss & R sided noci + thermoception. What part of the spinal cord has been damaged?
Left aside–>Brown-Sequard Syndrome