Motor Systems Flashcards
High motor neurons
Function: Strategy
Structures: association areas of neocortex, basal ganglia
From brain to spinal cord
Middle motor neurons
Function: Tactics
Structures: motor cortex,cerebellum
Low motor neurons
Function: execution
Strategy: brain stem, spinal cord
Exit spinal cord to innervated muscles
Axial muscles
movement of trunk
Proximal-gridle muscles:
shoulder, elbow, pelvis, knee
Distal muscles
hands, feet, digits (fingers/toes)
Smooth muscle- enteric
innervated by nerve fibers from the autonomic nervous system (ex: digestion and blood pressure)
Striated muscles
cardiac (heart) and skeletal
skeletal muscles
bulk of muscle mass- mediates movements, facial expression etc.
Amyotrophic lateral sclerosis- ALS (lou Gehrig’s)
muscle weakness/atrophy, slow deterioration of alpha motor neurons due to loss of superoxide dismutase, meaning they can’t break down free radials.
Excitotoxicity: glutamate overstimulation, treatment targets release of glutamate.
Muscular Dystrophy
Progressive weakness and muscle deterioration= genetic loss of dystrophin
Myasthenia Gravis
Autoimmune disease- nAChRs
Cortico/Rubrospinal tract functions.
Transmission of commands for skilled movements. Corrections of motor patterns generated by spinal cord.
Antigravity muscles are mainly _____ and ______
Paravertebral extensors
Proximal extensor arms of legs
Recticulospinal functions
- Activate spinal motor programs for steeping and other stereotyped movements
- upright body posture
Corticospinal tract crosses in ____. It controls distal musculature (extensors). What happens if it is lesion?
Crosses in pyramids.
If lesioned, can’t move limbs independently, voluntary movements are slow and inaccurate. Rubrospinal may compensate.
Rubrospinal Tract receives central input from ____ and crosses in the ____.
Cortex
Pons
Lateral Pathways control what?
Voluntary movements of distal musculature- primarily to flexors/extensors?
Ventral pathway functions
postural musculature. Originate in brainstem, use sensory info about balance and position to reflexively maintain balance and posture
Vestibulospinal pathway
Vestibular nucleus/labyrinth. Cranial Nerve 8. Control neck/back muscles down lumbar to facilitate extensor muscles of legs . Cerebellar inputs, no cortical.
Generation of tonic activity in antigravity muscles
Tectospinal
Originate in superior colliculus (tectum). head/neck posture and movement
Area 4- primary motor cortex M1
Wilder penfield
Stimulation leads to movement/twitching in arm/limb, motor output.
Area 6: PMA
What does it do, and where does it project to?
Premotor area: skill voluntary movement (sensory-motor associations). Projects to reticulospinal/proximal muscles.
Area 6: Supplementary motor area (SMA).
Also, what do lesion result in?
Sequences and bimanual coordination innervation to distal muscles.
Apraxia- inability to perform skilled movements.
What area has the lowest threshold for elicitation of the movements by electrical stimulation?
Area 4
Activity in M1 motor neurons encodes what two things?
Force and direction
What are the dopaminergic inputs that degenerate during Parkinson’s?
Those to the substantia nigra pars compacta= striatum
What disease results in HYPOkinesia (decreased movement) by degeneration of substantia nigra (pars compacta) resulting in tonic inhibition to thalamus?
Parkinson’s (more inhibition)
Bradykinesia
Slow movements (substantia nigra)
Akinesia
Difficulty in initiating willed movements (substantia nigra)
Rigidity
increased muscle tone (substantia nigra)
Tremors at rest
Subtantia nigra
What disease results in Hyperkinesia because of loss of neurons caudate-putamen and GP and loss of inhibitory input to thalamus?
Huntington’s (less inhibition)
Also dementia, personality changes
Dyskinesias
Abnormal, purposeless movements
Caudate-putamen, and GP
Chorea
spontaneous uncontrolled movements (Caudate-putamen, GP)
Ballism (or more common, hemiballism)
wild flinging of extremities., hyperkinesia.
Damage to subthalamic nucleus, loss of excitatory input to GP, facilitation of VLo. Did inhibition
Hyperkinesia means (increased or decreased) BG output?
Decreased
List that Basal Ganglia Planned movements pathway
input to thalamus (VLo) then to Area 6
List Cerebellum coordinated motor function pathway
input to thalamus (VLc) then to area 4, then project to layer 5, betz cells
Cerebellum inputs
spinal cord/brain stem, proprioceptive
inputs from cerebral cortex to coordinate motor outputs
Cerebellum outputs
thalamus, brainstem, spinal cord.
Cerebellum lesion ataxia
inaccurate, uncoordinated movements
Cerebellum functions
Motor Learning (learning motor sequences, multi-joint movements)
Coordinate movement (movement/balance)
Cerebellum Excitatory input from _____ and inhibitory output to _____.
Inferior olive
Deep Nuclei
Cerebellum: Vestibulocerebellum. Function and deep nucleus
Head/body in space, equilibrium, eye orienting
Fastigial nucleus
Cerebellum: Spinocerebellum: Function and deep nucleus
Control axial musculature through fastigial and vernal cortex.
Limb musculature through interposed nuclei and paravernal cortex
Interposed (globose and emboliform) deep nuclei
Cerebellum: Pontocerebellum (nocerebellum) Lateral
Precision and timing of movements of upper extremities (arms/legs), lateral hemispheres.
Dentate nucleus
Alpha motor neuron inputs
Spinal innervation
Sensory input from muscles spindles
Input from upper motor neurons in the brain
Muscle spindles function? (La sensory neurons)
Sense muscles length
In parallel
Largest and fastest axons
Gamma neurons ___intrafusiak fibers when extrafusial shorten
Contract
Gamma neurons _____ la activity
Increase
Myotactic reflex
Knee jerk, vibration, causes extension
La axon —> alpha motor neuron
Reverse myotactic reflex
Prevents muscle overload, keeps tension in optimal range
LB axon —> inhibitory interneuron, which inhibits alpha neuron.
Golgi neurons inhibit Lowe motor neurons
Reciprocal inhibition.
Contract one muscle with la axon, relax antagonistic muscles
Flexor reflex
Withdraw from pain
Crossed extensor reflex
Withdrawal of antigravity extensor muscles of leg opposite pain
Function of golgi tendon organ
Strain gauge, monitors muscles tension/congregation.
Synapses in central horn.
Lb axon active with alpha motor neurons.
Lesions in vestibulocerebellum
Unsteady
Drunk
Fall
Lesions in ponticerebellum
Hypotonia, ataxia
Intention tremor (when you reach for stuff)
In granular layer, ______ are excitatory, _______ are inhibitory
Granule
Golgi
Mossy fibers send glutamate to
Golgi and granule
Climbing fibers are excitatory, and aspartate synapse on _____ cells
Purkinje
Multilayered fibers are
Inhibitory
