Motor Systems - Lecture 6 Flashcards
fxns
movement
posture and balance
communication
what are the motor systems guided by
sensory systems
hierarchal motor system architecture
cortex
cerebellum
brainstem
spinal cord
motoneurons
muscles
upper motor neurons cell bodies
situated in the motor cortex
upper motor neurons project
axons via the corticospinal tracts to the spinal cord
where do UMN (upper motor neurons) synapse
anterior horn w/ lower motor neurons
lower motor neurons (LMN) project
axons via the peripheral nerves
what do the peripheral nerves do (LMN)
contact muscle fibers at the neuromuscular jxn
damage to UMN
spasticity
hyperreflexia
damage above decussation
damage below decussation
spasticity
excitation of extensors
damage above decussation
contralateral effects
damage below decussation
ipsilateral effects
lower motor neurons
motor neurons connecting the brainstem and SC to muscle fibers
bringing the nerve impulses from the UMNs out to the muscles
where does a LMN axon travel through
a foramen and terminates on an effector (muscle)
motor unit
nerve-muscle fxnal unit
alpha motor neuron and all the muscle fibers it supplies
number of muscle fibers per motor unit
can vary from a few (4-6) to hundreds (1200-1500)
muscles that control fine movements
have small motor units
large weight bearing muscles
have large motor units
alpha motor neuron
final common path for all movement
movement can be generated from
sensory signals in the muscles spindle like the stretch reflex
sensory signals from skin as in the pain withdrawal response
involuntary signals from the brainstem for posture, keeping us upright w/o conscious attention
signals from the brain for voluntary movement
3 classes of movement
voluntary
reflexes
rhythmic motor patterns
voluntary
complex actions –> reading, writing, playing piano
purposeful, goal oriented
learned –> improve w/ practice
reflexes
involuntary, rapid, stereotyped
–> eyeblink, coughing, knee jerk
graded control by eliciting stimulus
rhythmic motor patterns
combines voluntary and reflex acts
–> chewing, walking, running
initiation and termination voluntary
once initiated, repetitive and reflexive
organization of motor control
hierarchal
parallel
parallel
pathways active simultaneously
hierarchical control of movement –> 3 levels of control
SC
brainstem
cortex
hierarchical control of movement –> divisions of responsibility
higher levels
spinal cord
higher levels
general commands
SC
execution through skeletal muscles
what does each level of the control of movement receive
sensory input
hierarchical control –> SC
automatic and stereotyped responses
can fxn w/o brain
spinal interneurons
pathways converge on a motor neuron
automatic and stereotyped responses –> hierarchical control –> SC
reflexes
rhythmic motor patterns
spinal interneurons –> hierarchical control –> SC
same circuits as voluntary movement
pathways converge on a motor unit –> hierarchical control –> SC
final common path
hierarchical control –> brainstem
modulates neurons in SC to maintain balance and posture by interneurons and motor neurons
2 main parallel pathways
2 main parallel pathways –> hierarchical control –> brainstem
medial
lateral
medial –> hierarchical control –> brainstem
to ventromedial SC
postural/proximal muscles
lateral –> hierarchical control –> brainstem
to dorsolateral SC
manipulative/distal muscles
