L4 Motor learning and neurological syndromes Flashcards
Hierarchy of motor control
High: strategy
-Association areas of neocortex and basal ganglia
Middle: Tactic
Motor cortex, cerebellum
Low: Execution
-Brainstem and spinal cord
Corticospinal tracts
- Function
- Origin
- site of crossover
- PATHWAY: primary motor cortex>internal capsule>cerebral peduncle>pons> pyramid of medulla>Ant/Lat c.s tract
- Lateral tract: 80-90% decussate at pyramids (hands and fingers)
- Anterior tract: 10-20% decussate ipsilaterally at specific level of spinal motor neurons (muscles of upper leg and trunk)
- Destruction: loss of muscle strength, reduced manual dexterity
- Brodmanns Area 4 (and 6)
Reticulospinal tract
Ventromedial descending motor pathway
- Facilitates extension of limbs (upper arm)
- locomotion and postural control
Path:
- Originates in reticular formation of brainstem
- Descends down spinal cord to form medial [pontine] and lateral [medullary] tract
facilitate voluntary movement-medial tract
inhibit voluntary movement- lateral tract
Tectospinal tract
Ventromedial descending motor pathway
- controls muscles of the neck, upper trunk and shoulders
- coordinates head and eye movements
Path:
- Originates in superior colliculus in tectum
- Recieves visual information from retina and cortex
-Fibres cross in midbrain and travel down anterior white column of spinal cord- contralateral control
Rubrospinal tract
Lateral descending motor pathway
Activates flexor muscles in arms
PATH:
- origin-red nucleus
- crosses at midbrain
Vestibulospinal tract
Ventromedial descending pathway
Path:
-originates in vestibular nuclei of medulla [medial and lateral]
-sensory information originates from vestibular labyrinth in ear
-no crossing-remains ipsilateral
Medial tract
-controls head and neck movements
Lateral tract
- activates extensor muscles in arms and legs
- maintains upright and balanced posture
Tectospinal and medial vestibulospinal
Control head and neck movements.
Lateral vestibulospinal and reticulospinal
Activate extensor muscles in arms and legs.
Decorticate posturing
Due to lesion above the red nucleus
- Rubrospinal tract intact and more active as regulation from cortex is disrupted [disinhibition] therefore facilitate flexors in the UL
Decerebrate posturing
Causes extension in all limbs.
Mechanism:
- Lesion below the red nucleus, rubrospinal tract is inhibited due to disruption
- Upper limbs are extended due to activation of lateral vestibulospinal and reticulospinal tract
Stroke and posture
Stroke in middle cerebral artery can affect motor cortex and corticospinal tarct
- upper limb flexion
- lower limb extension
Other features
- Increased tone (spasticity),
- Brisk Reflexes (overactive reflex due to UMN lesion
- Babinski reflex
- Clonus(involuntary rhythmic contractions)
Corticobulbar pathway
FACE
involuntary decussate in pons movements of face, neck, tongue, eye -facilitates mastication -vocal cords/swallowing
Lower Motor Neuron lesion
Bell’s palsy
- Damage to CN7 motor nucleus beyond stylomastoid foramen (ipsilateral facial muscle paralysis)
- Facial asymmetry; Atrophy of facial muscles; Drooping of the mouth corner;
- Cannot taste in ant 2/3; Cannot close eye or stop welling up; Eyebrow droop;
- Lips cannot be held tightly together;; sound hypersensitivity;
- Flaccid paralysis of muscles; decrease superficial reflexes and tone; muscle atrophy; fasciculations
Upper Motor Neuron lesion
- Damage to neuronal cell bodies in cortex or their axons
- No voluntary control of contralateral lower facial muscles (voluntary control of forehead remains)
- Spasticity: exaggerated reflexes; hyperreflexia; clonus: jerky contractions following sudden muscle stretching; weakness; increase tone; Babinski’s sign; loss of voluntary movement
Parasagittal Meningioma
commonly neoplasm of the meninges
can press on specific areas of the motor cortex controlling legs
bilateral leg weakness and spasticity
