Motor Control Flashcards
Describe the pathophysiology of parkinsons?
Degeneration of the substantia nigra and there dopaminergic inputs to the striatum . Dopamine depletion = closing down of focused motor activities that funnel through thalamus to the SMA
What is a common symptom of parkinsons?
Hypokinesia
What is the pathophysiology of Huntingtons Chorea?
A loss of caudate, putamen and globys pallidus
What is the presentation of Huntington’s?
Chorea, dementia and personailty disorders
What do lateral pathways control?
Voluntary muscles of distal muscles - under cortical control
What do ventromedial pathways control?
Control posture and locomotion - under brain stem control
What do axons of CST do?
Control pools of spinal motor neurones by monosynaptically excitings pools of agonist motorneurones and inhibit antagonist motorneurones
How many ventromedial pathways control posture and locomotion?
2 - VESTIBULOSPINAL AND TECTOSPINAL
What does the VST do?
Stabilises head and neck
What does the TST do?
ensures eye remain stable as body moves
What do pontine and medullary reticulospinal tracts do?
Control trunk and antigravity muscles
Use sensory info to control balance and body position
Where is the primary motor cortex found?
The precentral gyrus
How is mental image of body in space generated?
By somatosensory, proprioceptive and visual inputs into areas 5 and 7
Where are decisions about movements made?
Prefrontal and parietal cortex
What happens on damage to descending motor pathways?
Immediate flaccidity of contralateral muscles - spial shock - as spinal circuits are deprived of cortical input. Spinal circuits can regain function and new connections sprout. e.g babinski’s sign, spasticity or loss of fine finger movements
What selects and initiates willed movements?
Basal ganglia motor loop
What makes up the corpus striatum?
The caudate and putamen
What is the function of the corpus striatum?
to recieve input from all over the cortex
What kind of axons lie within the corpus striatum?
Inhibitory axons to protext globus pallidus and substantia nigra
When does the putamen fire ?
Before limb/trunk movement
When do caudate fibres fire?
Before eye movement
What do globus pallidus neurones do at rest?
Inhibit VLo as they are spontaneously active
What happens during cortical exitation in the motor loop?
Putamen is excited which inhibits the globus pallidus which releases VLo from inhibition which boosts SMA activity
What happens when cerebellum lesions occur?
Ataxia
How does voluntary movement occur?
Via alpha motorneurones in spinal cord
How does reflex movement occur?
Via hard-wired motorneurone circuits at each segmental spinal level
What pathways regulate trunk and limb muscle reflexes?
Descending pathways from vestibulospinal and reticulospinal tracts
Name the 4 systems which control movement
Descending control pathways, basal ganglia, cerebellum and local spinal cord/brain stem circuits
How does the spinal cord recieve input?
Via descending input from the brainstem and directly via the pyramidal tract
Where are the CST areas found in the cortex?
Areas 4 and 6 of the frontal motor cortex
Where do axons of the CST desuccate?
Medulla and spinal cord
Where do axons of the CST synapse?
Ventral horn motor neurons or interneurons
What do Upper Motor Neurons in cortex target?
Lower Motor Neurons in the spinal cord
How are decisions into motor movements made?
Sensory info is input into areas 5+7, parietal and prefrontal cortex make decisions on what movements to make, axons converge onto area 6, encoding how to carry out desired actions
What is a positive Babinski’s sign indicative of?
Incomplete upper control of spinal circuits (a.k.a UMN lesion and damage to Corticospinal Tract)
What does spasticity indicate?
Removal of inhibitory reflexes of UMN, usually due to a lesion of UMN
