Lecture 18- Motor control, cortex and allied structures Flashcards
What are the different levels of integration?
Spinal cord- reflexes
Subcortical- medial/ventral sc paths, medial cerebellum - reproduction
Cortical- lateral sc pathways, lateral cerebellum- science, art etc
Rubrospinal tracts
originates from the red nucleus, a midbrain structure.
as the fibres emerge, they decussate (cross over to the other side of the CNS), and descend into the spinal cord. Thus, they have a contralateral innervation.
thought to play a role in the fine control of hand movements
Reticulospinal tracts
- The medial reticulospinal tract arises from the pons. It facilitates voluntary movements, and increases muscle tone.
- The lateral reticulospinal tract arises from the medulla. It inhibits voluntary movements, and reduces muscle tone.
Vestibulospinal tracts
Medial and lateral- arise from vestibular nuclei of the medulla, travel ventrally in spinal cord
Innervate neck and antigravity muscles (flexors of arm, extensors of leg)
Tectospinal tract
Originates in superior colliculus of midbrain and controls eye movements.
Where are the sensory and motor homunculi located?
Postcentral gyrus
Precentral gyrus
What are the roles of the premotor cortex and supplementary motor areas?
Premotor- set posture appt. to movement, aid in selecting movement
Supplementary- integrating COMPLEX, PLANNED patterns of movement
Corticospinal tracts
Main descending tracts responsible for motor control
Most travel from cortex to pyramids in medulla, > lateral corticospinal tracts to innervate distal muscles responsible for fine control
ventral corticospinal tracts control proximal muscles responsible for posture
Where do motor neurons innervating face travel in
Corticobulbar tracts
30% pyramidal neurons from primary motor cortex, 30 from premotor/supp and from 40 in partietal assc. area/ primary somatosensory area
What is the final common path for UMN
LMNs- neurons eventually innervate a motor unit which can receive input from many neurons
UMN lesions
most common is cerebral stroke- removes higher control over midbrain reflexes, can result in hyperactive stretch reflexes, spastic rigidity of flexors in UL and extensors in lower limbs and positive babinski’s sign
What are the 5 components of the basal ganglia?
5 pairs of nuclei
Caudate nucleus, putamen, globus pallidus, substatia nigra and subthalamic nuclei
Feed output to motor/assc. of cerebral cortex via thalamus and receive cortical input
What are some conditions associated with the basal ganglia?
Parkinsons- excessive suppression
Huntington’s, parkinsons, tourettes- excessive release
Impacts preprogrammed movement and behaviours (speech in tourettes)
Putamen circuit
Feeds via loop from cortex > putamen > GP > SN > thalamus > cortex
Problems give rise to twisting, bending movements of hands face arms or neck, flailing of whole limb and flickering of hands and face
Caudate circuit
Cognitive control of motor pattern sequences- maintained by projection between SN and striatum, problems often arise duet to hyperactivity or depression of dopaminergic connetction between them
