Motor Control - Cortex and Allied Structures Flashcards
Describe in more detail the cortical and sub-cortical levels of integration.
Cortical level - lateral cerebellum + lateral SC pathways; phylogenetically new; distal limbs (fingers); fine controlled movement
Sub-cortical - medial and ventral SC pathways and medial cerebellum; phylogenetically old - proximal limbs - posture - primitive
Describe the rubrospinal motor tract.
- Info from motor cortex and cerebellum through red nucleus
- lateral motor system, despite being more primitive
- feeds to spinal CPG
- sets baseline posture, but influenced by motor cortex
- UMN lesions result in spastic posture
How do UMN lesions cause spastic posture?
Rubro-spinal or reticulospinal tract set baseline posture without influence from motor cortex as it has been damaged e.g from a stroke
- stroke in L brain, R upper limb flexed, R lower limb extended
Describe the reticular and vestibulospinal motor tracts.
- Reticular nucleii - pons excitatory to stretch reflexes in spinal cord; medulla inhibitory to stretch reflexes; antigravity + posture
- Vestibular nucleii - receive input from vestibular apparatus from inner ear
- position of head, neck, posture
- Both have input from cortex and cerebellum - maintain balance
- Both medial tracts
What is included in the premotor cortex and supplementary motor cortex? What is their role?
Hand skills, head rotation, contralateral eye movements, Broca’s area (word formation)
- mostly in frontal lobe
- involved in planning movement + specific, fine types of movements
What other area of cortex send info to motor cortex?
- Somatosensory cortex
- Visual cortex
- Auditory cortex
- Thalamus (tactile signals, joint and muscle signals, signals from cerebellum, basal ganglia
- Wernicke’s area (understanding of words)
What is the role of the motor cortex?
- the manager
- command signals which trigger complex movements patterns - involves activation or inhibition of multiple spinal cord motor neurones
- control of movements, not individual muscles
What is a lower motor neuron?
Motor nerve innervating motor unit - LMN
- may receive input from many UMNs
What makes up the basal ganglia?
groups of neurons
- putamen
- caudate nucleus
- subthalamic nucleus
- substantia nigra
- globus pallidus
Where do virtually all motor fibres pass through?
Internal capsule - the space between caudate nucleus and putamen
Describe the putamen circuit.
Loop from cerebral cortex and back via putamen - globus pallidus - subthalamic nucleii - substantia nigra, thalamus
- pre-programmed movement patterns
- inhibitory
What problems can occur with damage to putamen circuit?
Athetosis (wriggling), ballismus (large, exaggerated movement), chorea (dance-like movement)
Describe the caudate circuit.
Cognitive control of movement
- inhibitory
What is common to both the caudate and putamen circuit?
An excitatory dopaminergic pathway from substantia nigra to striatum (caudate nucleus + putamen)
How are these basal ganglia circuits affected by Parkinson’s?
Inhibition of inhibition pathway from striatum to GP turned off and inhibition of excitation pathway from SN to striatum due to degeneration of neurons
- Results in less movement as movement initiation is compromised
