motor systems Flashcards
parts of the motor system
the parts of the nervous system that contribute to movement of the body: cerebral cortex, brain stem, spinal cord
Sensory: info enters sensory systems thru receptors, physical energy is transformed into neural signals and information ascends thru neural pathways tracts to cortex. Generates an internal representation of the world
Motor: programming begins in the cortex and lower CNS levels and the information is sent down thru stages to ultimatley moce muscles (effector). Motor processing begins with an internal representation of the desired movement. neural signals are transformed into contractile force in muscles
motor control hierarchy
smaller simpler elements at sp cd are integrated into more complex patterns at higher levels of the NS. successively higher levels of the motor hierarchy specify increasingly more complex aspects of a motor task
higher motor commands with sensory input ultimately influence the final common path to cause movement. Even easy movements
modulation of movement in subcortical structures
- basal ganglia, cerebellum
the thalamus is a relay station for information from the basal ganglia–> cortex and the cerebellum->cortex
spinal cord
spinal motor neurons execute movement (bottom of heirarcy)
2 types
1. motor neurons in ventral horn that project to muscles and ultimately cause the muscle to contract via lower motor neurons (the final common pathway)
Interneurons in the intermediate zone: segmental interneurons that project within a single spinal cord level, propriospinal interneurons that transmit information between multiple spinal cord levels. interneurons project to motor neurons. they form circuits that help connect and coordinate motor neurons that contract groups of muscles for specific tasks
Somatotopic organization of the spinal cord
medial motor neurons innervate proximal muscles that control balance, posture, and movement of trunk
lateral motor neurons innervate distal muscles that control limbs and digits and control specific limb digit movement
brainstem
modulates the action of spinal motor circuits
2 general types of neurons
- Motor nuclei with motor neurons that directly innervate facial muscles via lower motor neurons (facial nucleus)
- modulate spinal cord: many groups of neurons that project down and terminate on neurons in the spinal cord gray matter. upper motor neurons. medial and lateral descending brainstem pathways (tracts) named based on origin and endpoints
medial brainstem pathways
reticulospinal
Vestibulospinal
Tectospinal
tracts are named based on origin and end points. Tracts descend in medial ventral white matter and terminate in the ventromedial ventral spinal cord. influence axial, proximal muscles–provides basic postural control where the cortex can organize more highly differentiated movement
lateral brainstem pathways
rubrospinal tract (Red nucleus–> spinal cord) tract descends in dorsolateral white matter and terminates in the dorsolateral area of the VENTRAL SPINAL CORD
–modulates goal directed movements like reaching and manipulating
Cerebral cortex
modulates action of motor neurons in the brainstem and spinal cord (top of hierarchy)
gives the ability to organize complex motor acts and execute fine movements with great precision
plans movements, coordinates their execution, gives descending commands to motor neurons in sp cd and brainstem via upper motor neurons
primary motor cortex, premotor cortex, supplementary motor area
primary somatosensory (regulates incoming sensory information in the dorsal horn) and posterior parietal cortex (helps localize where an object is with respect to body)
primary motor cortex
executes commands to motor control, controls individual finger movements coordinates the force and direction of movements, contains somatotopic map of body parts on opposite side
premotor cortex
integrates motor movements with sensory input (mainly from visual system). Coordinates complex sequences of movement (motor learning)
supplementary motor area
importent in internally driven, will driven movements formulate an intention to make a movement
cerebral cortex acts on motor neurons via 2 descending pathways
- lateral corticospinal tract- contralateral limb, digits, goal directed reaching
- Ventral corticospinal tract: neck trunk muscles, postural control
hierarchical motor system organization
Cortex-> brainstem-> sp cd -> muscle movement
lower neural structures are are concerned with more simple tasks (reflexes…withdrawal from painful stimulus occurs w/o thinking about it)
complex, voluntary neuromuscular tasks require higher order brain structures (deciding to throw the ball to first or second base to make an out)
parallel motor system organization
different systems operate in parallel. parallel motor pathways exist between the cortex and sp cd (corticospinal tracts) and the brainstem and spinal tracts
so when cortical, brainstem, sp cd lesions occur, there are alternative pathways that can partially compensate and carry out motor tasks such that person can still have basic motor functions. redundancy gives flexibility and plasticity to occur after injury
