Descending motor control

The corticospinal and corticobulbar tracts are ____ ____ motor tracts that are part of ____ ____ control and ____ in the ____ ____ and ____ the _____ __

The corticospinal and corticobulbar tracts are lateral descending motor tracts that are part of volitional motor control and converge in the corona radiata and enter the internal capsule

40% of fibers from the corticospinal and corticobulbar tracts are from the ____ ____ ___

Ascending somatic sensory fibers from the _____

40% of fibers from the corticospinal and corticobulbar tracts are from the primary motor area (4)

Ascending somatic sensory fibers from the thalamus

In the midbrain, fibers of the corticospinal tract reside in the _____ ____ of the _____ ____ and innervate the ____ ____

in the brainstem they also innervate the ______ _____ and _____ ___

In the midbrain, fibers of the corticospinal tract reside in the middle 2/3rds of the cerebral peduncle and innervate the red nucleus

In the brainstem they also innervate the contralateral pontine and medullary nuclei

The corticospinal tract controls most of the ____ ____ especially the ____

Controls most of the manipulative movements especially the digits

The corticobulbar tract exits the _____ to connect with ____ ____ _____ ___

Cortical inputs to the _____ ____ of ____

Upper half is ____

Lower half is ____

The corticobulbar tract exits the brainstem to connect with motor based cranial nerves

Cortical inputs to the motor nucleus of VII

upper half is bilateral

lower half is contralateral

Rubrospinal tract originates from the ____ ____ of the ____ ___

Immediately descends through the _____ of the _____ side

Descends with the _____ _____

Terminates in ___, ___, ___ of the ____ ___

Descend only to the ____ and ____ ____ levels

Rubrospinal tract originates from the magnocellular portion of the red nucleus

Immediately descends through the brainstem of the contralateral side

Descends with the lateral corticospinal cord

Terminates in V, VI, and VII of spinal cord

Descends only to the cervical and high thoracic levels

The tectospinal tract has ____ axons that arise from cells in the _____ _____ ___

Axons descend to the _____ level

Terminate in ____, ____ and parts of ____

Mediates movements in response to _____ stimuli

Fibers terminate on _____ that regulate ____ ___

Regulate ____ of the ____ during tracking of ___ ____

The tectospinal tract has descending axons that arise from cells in the contralateral superior colliculus

Axons descend to the cervical level

Terminate in VII, VIII, and parts of VI

Mediates movements in response to auditory stimuli

Fibers terminate on motorneurons that regulate neck muscles

Regulate orientation of the head during tracking of moving objects

Medial descending tracts include the _____ and _____ _____ formation


These function to mediate _____ _____ control

Pontine and medullary reticular formation

These function to mediate postural motor control

The pontine (medial) reticulospinal tract _____ motorneurons to _____ muscles

descends ____

This receives input from the ____ ___, ____ ___, midbrain ____ centers and ____

Also receives significant input from ______ ___-

The pontine (medial) reticulospinal tract excites motor neurons to antigravity muscles

Descends uncrossed

This receives input from the cerebral cortex, red nucleus, midbrain locomotor centers, and cerebellum

Significant input from ascending afferents

the medullary (lateral) reticulospinal tract descends _____ and _____ motorneurons to _____ muscles

Cells are driven by input from the ____ ___ and _____ _____ Muscle function

the medullary (lateral) reticulospinal tract descends uncrossed and inhibits motorneurons to antigravity muscles

Cells are driven by input from the cerebral cortex and inhibit flexor muscle function

The vesitbulospinal tracts are located in the _____ _____ nucleus

Axons descend ____ in the _____ ____

Tract _____ motorneurons to _____ muscles

Primary input from the ____ _____ and ____

The vestibulospinal tracts are located in the lateral vestibular nucleus

Axons descend uncrossed in the lateral funiculus

Tract excited motorneurons to antigravity muscles

Primary input from the vestibular apparatus and cerebellum

The descending MLF descends _____ and innervates motorneurons to the _____

Involved in _____ and _____ orientation

Input from the ______ ____ and _____

Starts in the _____ _____ nucleus

The descending MLF descends ipsilaterally and innervates motorneurons to the neck

Involved in coordination and head orientation

input from the vestibular apparatus and cerebellum

Starts in the medial vestibular nucleus

Both the descending MLF and the vestibulospinal tracts are key in ____ and _____ regulation of ____

Key in static and dynamic regulation of posture

The medial tracts including the _____ and _____ tracts project _____ and are _____ ______ and ____ motorneuron pools to _____, _____ muscles to control ______, _____ mechanisms, and _____ tone

The medial tracts including the reticulospinal an vestibulospinal tracts project ipsilaterally and are tonically active and excite motorneuron pools to antigravity, extensory muscles to control posture, righting mechanisms, and muscle tone

The lateral tracts including the ______ and _____ tracts project _____ and exhibit _____ activity to _____ motorneurons and regulate _____ ___, _____, _____ ____ movements

The lateral tracts including the corticospinal and rubrospinal tracts project contralaterally and exhibit phasic activity to excite motorneurons and regulate finely controlled, manipulative, phasic volitional movements

Decerebrate posture leaves the _____ ___ and _____ ____ intact but removes the descending _____ and ____ ____ input

results from ______ ______ lesions

Disruption to the ____ and _____ tracts

Interruption of _____ ____

_____ reflex patterns remain

____ and ______ muscle tone ____ dramatically

_____ and ______

____ muscles firing ______ _____

Decerebrate posture leaves the lower brainstem and spinal cord intact but removes the descending cerebral and red nucleus input

Results from upper brainstem lesions

Disruption to the cortico and rubrospinal tracts

Interruption of voluntary movements

Postural reflex patterns remain

DTR and extensor muscle tone increased dramatically

Hyperreflexia and spasticity

Postural muscles firing without inhibition

Decorticate posture results from ______ lesions

Exaggerated _____

Weakness of ____ ____ movements in ______ ___

Development of ____

_______ upper limb is ____ while _____ lower limb is _____

_____ baby

Decorticate posture results from cortical lesions

Exaggerated DTR (spasticity)

Weakness of very fine movements in distal extremities

Development of babinski

Contralateral upper limb flexed while contralateral lower limb extended

Mummy baby

Decerebrate vs decorticate posture?

Decerebrate = extensors upper and lower are firing

Decorticate = flexors up top, extensors down bottom