Motor Organization of the
Spinal Cord
Objectives
components of the motor system
pyramidal pathways
extrapyramidal pathways
spinal reflexes
upper and lower motor neurons
spinal cord trauma
Functions of motor system
Plan
assimilate all the sensory information and generate a plan
for appropriate motor activity
this is done in the premotor area. brodmann's area 6
Execution of plan
plan should be sent to motor area from where descending
fibers arise
this is achieved by the primary motor area. brodmann's area
4
passage of impulses through descending fibers, to reach to
anterior horn of spinal cord. corticospinal tracts
alpha motor neurons
Components of the motor system
Motor Organization of the Spinal Cord 1
, Motor cortex
plans the motor activity
site of origin of descending fibers. corticospinal tract
Basal ganglia and cerebellum
helps the cortex for planning and execution of motor
activity
Descending fibers/pathways
carry impulses from motor cortex to spinal cord
Spinal cord and brainstem
"plans" for many of the basic motor activities are stored
eg. withdrawal reflex, walking movement, chewing
movement
Efferents
present in peripheral nerves
carries impulses from spinal cord to muscles
these are the lower motor neurons
Role of spinal cord
ventral horn is the source of the efferent
some reflexes are complete at the level of the spinal cord
like stretch reflex, withdrawal reflex, positive supportive
reflex, defecation reflex, micturition reflex
background activity and postural control, fine movements
Motor Organization of the Spinal Cord 2
Spinal Cord
Objectives
components of the motor system
pyramidal pathways
extrapyramidal pathways
spinal reflexes
upper and lower motor neurons
spinal cord trauma
Functions of motor system
Plan
assimilate all the sensory information and generate a plan
for appropriate motor activity
this is done in the premotor area. brodmann's area 6
Execution of plan
plan should be sent to motor area from where descending
fibers arise
this is achieved by the primary motor area. brodmann's area
4
passage of impulses through descending fibers, to reach to
anterior horn of spinal cord. corticospinal tracts
alpha motor neurons
Components of the motor system
Motor Organization of the Spinal Cord 1
, Motor cortex
plans the motor activity
site of origin of descending fibers. corticospinal tract
Basal ganglia and cerebellum
helps the cortex for planning and execution of motor
activity
Descending fibers/pathways
carry impulses from motor cortex to spinal cord
Spinal cord and brainstem
"plans" for many of the basic motor activities are stored
eg. withdrawal reflex, walking movement, chewing
movement
Efferents
present in peripheral nerves
carries impulses from spinal cord to muscles
these are the lower motor neurons
Role of spinal cord
ventral horn is the source of the efferent
some reflexes are complete at the level of the spinal cord
like stretch reflex, withdrawal reflex, positive supportive
reflex, defecation reflex, micturition reflex
background activity and postural control, fine movements
Motor Organization of the Spinal Cord 2
