Upper motor neurons Flashcards
What does the medial group control?
Axial and girdle musculature, so:
- posture
- locomotion
- proximal components of reaching movements
What are the medial tracts?
reticulospinal
tectospinal
vestibulospinal
ventral corticospinal
What is the lateral group made up of?
rubrospinal
lateral corticospinal
What does the lateral group control?
limb movement
involved in precision grip and palpation
Draw the descending tracts
OneNote
Mnemonic for descending tracts
Cleopatra May Think Provided Vain Monks Riot Calmly.
- anterior Corticospinal
- Medial longitudinal fasciculus (includes the medial vestibulospinal)
- Tectospinal
- Pontine reticulospinal
- lateral Vestibulospinal
- Medullary reticulospinal
- Rubrospinal
- lateral Corticospinal
What is another name for pyramidal tracts?
Corticospinal
What is another name for extrapyramidal tracts?
Extra-corticospinal
Describe briefly the pyramidal tracts
- originate in the cerebral cortex
- carry motor fibres to the spinal cord and brainstem
- responsible for the voluntary control of the musculature of the body and face
Describe briefly the extrapyramidal tracts
- Originate in the brain stem
- Carry motor fibres to the spinal cord
- Responsible for involuntary and automatic control of musculature (such as muscle tone, balance, posture and locomotion
Do the cerebellum and basal ganglia send projections down into the spinal cord?
No, they send neurons which modulate the descending information
Where do the pontine and medullary reticulospinal tracts originate?
In the pontine and medullary reticular formations respectively in the
Describe pontine reticulospinal tract
- travels ipsilaterally in the ventral funiculus
- enhances the antigravity reflexes of the spinal cord, facilitates AXIAL AND PROXIMAL EXTENSORS OF THE LOWER LIMB and maintains a standing posture
Describe the medullary tract
- projects contralaterally in the anterolateral funiculus
- liberates the anti-gravity muscles from reflex control - inhibits reflexes
- FLEXOR MUSCLES
What is the reticular formation?
- series of interconnected nuclei in brainstem from upper midbrain to lower medulla
Input to pontoreticulospinal
No cerebral cortex
Ascending pathways
Input to medullary reticulospinal
Cerebral cortex - corticoreticular fibres
Ascending tracts
What does the vestibulospinal tract comprise?
Lateral and medial branches
Where does the vestibulospinal tract originate?
Vestibular nuclei of the medulla
- the medial tract originates in the medial vestibular nucleus (Schwalbe’s nucleus)
- the lateral tract originates in the lateral vestibular nucelus (Deiter’s nucleus)
What do the vestibular nuclei receive input from? What do these signal?
The semicircular canals and otolith organs of the inner ear
- Head position and movement via the auditory nerve
- also receive input from the cerebellum (fastigial nucleus w/proprioceptive information)
How do the vestibulospinal tracts travel?
- both ipsilaterally in the ventral funiculus
- smaller medial tract innervates axial muscles in the cervical region controlling neck movements
- the larger lateral tract descends as far as the lumbar spinal cord → fascilitates antigravity (EXTENSOR) motor neurones, especially axial ones, and helps to maintain posture by controlling postural muscles (e.g. the hip, back and shoulder muscles)
Which tracts do extensor muscles?
Vestibulospinal tract
Ponto-reticulospinal tract
Which tracts to flexor muscles?
Rubrospinal tract
Medullo-reticulospinal tract
Where does the superior colliculus receive input from?
- retina
- also somatosensory and auditory inputs
Where does the superior colliculus receive input from?
- retina
- also somatosensory and auditory inputs
Where does the tectospinal tract end? What does it innervate?
At the cervical level
Muscles of the neck, shoulder and upper trunk
Main functions of the tectospinal tract
Coordinating head and neck movement
Mediating gaze
Where does the superior colliculus receive input from?
- retina
- also somatosensory and auditory inputs
Where does the tectospinal tract end? What does it innervate?
At the cervical level
Muscles of the neck, shoulder and upper trunk
Where does the rubrospinal tract terminate? What does it do?
Cervical spinal levels
Arm movements
Biased towards flexion movements
End on interneurons
Where does the rubrospinal tract originate?
Red nucleus of the midbrain, primarily from the caudal magnocellular part
Where does the rubrospinal pathway decussate?
Midbrain - ventral tegmental decussation
What are the two corticospinal tracts?
Ventral and lateral
Where does the rubrospinal pathway decussate?
Midbrain - ventral tegmental decussation
Where is the primary motor cortex?
In the precentral gyrus
What is on either side of the medullary pyramid?
Medullary olives
Where is the primary motor cortex?
In the precentral. gyrus
What is on either side of the medullary pyramid?
Medullary olives
Where do the corticospinal tract decussate? What percentage decussate?
At the medullary pyramids - 80%
What happens to the corticospinal fibres that decussate at the medullary pyramids?
They go into the lateral columns and become the lateral corticospinal tracts
What happens to the corticospinal fibres that DON’T decussate at the medullary pyramids?
Goes down the anterior white column
Becomes the ventral cortispinal tract
Cross over to the opposite ventral grey horn to stimulate lower motor neurones
What is the lateral corticospinal tract associated with?
Distal limb musculature
Fine and precise movements
What is the anterior corticospinal tract associated with?
Axial musculature
Gross/large movements
Path of ventral corticospinal tract
Internal capsule Crus cerebri Pons Pyramid Ipsilateral ventral funiculus
Path of lateral corticospinal tract
Internal capsule Crus cerebri Pons Pyramid Contralaterally in the lateral funiculus
What does the supplementary motor area do?
Relays inputs from the basal ganglia via the thalamic ventral anterior nucleus
Also receive input from the prefrontal lobe and is important in internally-generated movements
What is Brown Sequard syndrome?
lateral hemisection of the spinal cord where there is:
- loss of pain and temperature contralaterally due to the decussation of nociceptive inputs in the spinal cord
- sensory loss ipsilaterally due to the lack of decussation
- motor impairment ipsilaterally due to decussation at higher points of the majority of motor input to the descending tracts
What is anterior cord syndrome?
- lesion in anterior portion of the spinal cord
- dorsal column is left intact (retains proprioception and vibratory sensation)
- motor and nociceptive function is lost due to entire lesion bilaterally of both anterior segments of the spinal cord
Draw a section of the spinal cord - ascending and descending tracts
OneNote
What is anterior cord syndrome?
- lesion in anterior portion of the spinal cord where the dorsal column is left intact, but complete motor and nociceptive function is lost due to entire lesion bilaterally of both anterior segments of the spinal cord
Compare LMN and UMN lesions
LMN - everything is downregulated: - flaccid - less muscle contraction - hypotonic - less muscle tone - hyporeflexic - less muscle reflexes - denervation atrophy - less muscle innervation - Babinski negative - toes point down UMN - everything upregulated: - Spastic - more - Hypertonic - more - Hyperreflexic - more - Disuse atrophy - more - Babinski positive - toes point up
What is central cord syndrome?
- loss of nociceptive fibres bilaterally due to effect of decussation
- impairment of function of nerves that mediated tendon reflexes
- size of lesion determines subsequent effects
- greater motor loss in upper limbs than lower limbs
Compare LMN and UMN lesions
LMN - everything is downregulated: - flaccid - less muscle contraction - hypotonic - less muscle tone - hyporeflexic - less muscle reflexes - denervation atrophy - less muscle innervation - Babinski negative - toes point down UMN - everything upregulated: - Spastic - more - Hypertonic - more - Hyperreflexic - more - Disuse atrophy - more - Babinski positive - toes point up
