Descending Motor Control

alpha motor neruons

org from medial to lateral accoding to muscle grps innervated

muscle of trunk and proximal limbs

represented medially

ex shoulder

muscle of distal limbs

represented laterally

ex arm, hands, fingers

motor neruons

grped along length of spinal cord

somas of neruons

innervate given muscle bicep be found many sequential spinal cord segments

cervical enlargement

motor neuron pools for arms and hands

lumbar enlargement

motor neuron pools for legs feet

local circuit neurons

interact with motor neurons in different segments of the spinal cord

meidal local circuit neurons

project over many spinal cord segments as well as bilaterally to coordinate left/right and upper/lower body movement as well as posture

lateral local circuit neurons

project fewer segments and unilaterally to coordinate fine, independent muscle movements

Descending pathways from cortex to spinal cord

axons of upper motor neruons in corticospinal tracts synapse with interneurons and lower motor neurons in ventral horn of spinal cord

descending inputs

upper motor neurons of motor cortex corticospinal tract

porject both local circuit and lower motor neurons

coordinate both gross and fine motor movements

Superior colliculus

movement that orients eyes head and body toward sensory stimuli

Vestibular nuclei

reflexive changes in posture

reflexive eye movements

Reticular formation

anticipatory changes in posture

medial white matter

made up byt the vestibulo, reticulo, colliculospinal tract

Primary motor cortex

located in the precentral gyrus

stim directly evokes movement

lowest threshold for initiation of movement

contains map for musculature of body

contains map for movements

\