Unit 3: Overview Of Motor Control/Motor Disturbances Pg. 117 - 120 Flashcards
α motor neurons innervate
Extrafusal muscle fibers
γ motor neurons innervate
Intrafusal muscle fibers in NM spindles
Supranuclear motor control area of brain and brainstem comprised of
UMNs and pathways → influence LMNs (gamma reflex loop)
The cerebellum and basal ganglia (accessory motor control areas) function by
Influencing other supranuclear motor control areas and UMNs in those areas
Disturbances of motor control can be from these general categories
- cerebellar disturbances
- basal ganglia disturbances
- ‘pure lesion’ of pyramidal system
De-afferent
To cut sensory fibers
Interruption of sensory innervation of skeletal muscle (de-afferent) results in
- No paralysis of muscle
- Hypotonia
- Hyporeflexia (loss of DTR)
Note: about hyporeflexia. When there is no sensory innervation, there is no sensory innervation, and no deep tendon reflex (DTR)
What starts deep tendon reflex (DTR)?
Sensory information
Lower motor neuron lesion may be caused by
- Poliomyelitus (virus destroys LMNs in spinal cord ventral horn or brainstem motor nuclei)
- Peripheral nerve injuries
Lower motor neuron lesion results may
- decrease/loss in muscle tone
- paralysis or paresis of affected skeletal muscles
- weak or absent DTR
- muscle atrophy
Upper motor neuron lesion may be caused by
Lesion in CNS that interrupts many descending motor control pathways that exert control on LMNs
Unilateral UMN lesion above pyramids would result in typical signs _____ to the lesion
Contralateral
Unilateral spinal cord UMN lesion below the pyramids would disrupt motor control ____ to lesion
Ipsilateral
Initially during a period of spinal shock after an UMN lesion, what are the transient signs?
- Flaccid paralysis or paresis
- Hypotonia
- Hyporeflexia
Eventually after a period of several weeks after an UMN lesion, what are the “permanent” signs?
- Voluntary movements are weak (paresis) or absent (paralysis)
- Tone of muscles is increased beyond normal = hypertonia
Hypertonia
Tone of muscle is increased beyond normal
What does hypertonia from a UMN lesion lead to?
Spasticity of musclesa
Why does spasticity of muscles happen in UMN lesions?
A loss inhibition from descending pathways on the gamma reflex loop and the stretch reflex
UMN lesions result in
Spastic paralysis of anti-gravity muscles
Hypereflexia
Deep tendon reflexes are exaggerated
After UMN lesion, limb positions will become abnormal. Upper extremity in cerebral lesion?
Flexed
After UMN lesion, limb positions will become abnormal. Upper extremity in spinal cord lesion?
Flexed
After UMN lesion, limb positions will become abnormal. Lower extremity in spinal cord lesion?
Extended (variable)
UMN lesion limb positions
Uptight, spastic paralysis
LMN lesion limb positions
Hanging, loose, flaccid
In UMN lesion, only muscles of facial expression of the contralateral lower 1/2 of the face and muscles of the contralateral tongue are involved because
- LMNs that innervate these muscles usually receive contralateral C-B/C-N (UMN) innervation
- all other cranial nerves receive bilateral C-B/C-N (UMN) innervation
Typical and atypical signs : Babinski sign
Typical: toes plantarflex
Atypical: toes (big toe) spread and dorsiflex
Typical and atypical signs : Hoffman sign
Typical: no movement of fingers
Atypical: addiction or flexion of human and/or index finger
Typical and atypical signs : abdominal reflex
Typical: brief contraction of muscle — umbilical moves toward stimulus
Atypical: no abdominal muscle movement
Cremasteric reflex in infants
Soft touch on inner, upper thigh will result in cremaster muscle contraction
Quadriplegia/tetraplegia
Paralysis of all four extremities
Hemiplegia
Paralysis of half of body (L or R) both upper and lower extremity
Paraplegia
Paralysis of both lower extremities
Monoplegia
Paralysis of a single extremity
Unilateral CNS lesions above pyramids results in
Contralateral spastic paralysis
Hemiplegia or monoplegia (depending on lesion location)
Spinal cord lesion: complete transaction of middle cervical cord
Bilateral spastic paralysis
Quadriplegia
Loss of all somatosensation below level of lesion
Spinal cord lesion: complete transaction of thoracic cord
Bilateral spastic paralysis
Paraplegia of lower extremity
Loss of somatosensation below level of lesion
Spinal cord lesion: hemisection of cord
Called: Brown-Sequard syndrome
Motor:
- Flaccid paralysis at level of lesion on ipsilateral side
- Spastic paralysis below lesion on ipsilateral side
Loss of all Somoatosensation below level of lesion:
- ipsi loss of fine touch, prop, vibration
- contra loss of noci, temp, crude touch
Loss of noci, temp, crude touch at level of lesion — ipsi and contra sides
