Motor pathways Flashcards
What are the motor tracts in the lateral spinal cord? Where does each tract originate? What type of motor movement does it control?
Lateral corticospinal tract (pyramidal tract) - originates from the motor and sensory cortex, decussates at the medulla and descends contralaterally. Responsible for fine motor control of distal muscles.
Rubrospinal tract - originates in the red nucleus of the midbrain, decussates in the midbrain and descends contralaterally. Responsible for facilitating flexor alpha-motor neurons and inhibiting extensor alpha-motor neurons.
What are the motor tracts in the medial spinal cord? Where does the tract originate? Where does the tract go? What motor movement is the tract responsible for?
Tectospinal tract - originates in the superior colliculus (midbrain) and ends high in the cervical spinal cord. It is responsible for facilitating neck rotation in the direction of visual, auditory or somatosensory stimulus.
Lateral vestibulospinal tracts - originate in the vestibular nucleus (pons) and facilitate axial extensor (anti-gravity) muscles to maintain posture
Medial vestibulospinal tract - originates in the vestibular nucleus and facilitates neck extensor muscles to maintain posture
Lateral reticulospinal tract - originates in the reticular nucleus and maintains posture by inhibiting axial extensors
Medial reticulospinal tract - originates in the reticular nucleus and maintains posture by facilitating axial extensors
What tracts and structures are involved in maintaining posture and modulating posture during movement?
Lateral vestibulospinal tract and medial reticulospinal tract maintain tonic excitation of the anti-gravity (extensor) muscles.
Inhibitory input from the cerebellum and cortex balances the excitation of the extensor muscles.
Cerebellum inhibits the lateral VST -> reduces excitation of the extensor muscles
Cerebral cortex continually stimulates lateral reticulospinal tract -> inhibits the extensor muscles
What are the clinical signs of spasticity? Damage to what structures lead to spasticity?
hyperactive myotactic reflexes (hyperreflexia)
hypertonus of anti-gravity muscles (extensors on axial skeleton but flexors in arms)
“clasp-knife” type of resistance - initial, strong resistance to passive manipulation, which decreases and disappears as manipulation is maintained
Usually due to damage to the motor cortex and internal capsule
What are the clinical signs of rigidity? Damage to what structures lead to rigidity?
hypoactive myotactic reflexes (hyporeflexia)
hypertonus that is equally evident in both flexors and extensors
“cog-wheeling”
Usually caused by damage to the basal ganglia, Parkinson’s disease
