anatomy 403: neuro 3

direct motor pathways

• somatic = voluntary = skeletal muscle

• motor cortex: contains upper motor neurons

  • the primary motor area of the cerebral cortex is responsible for initiation of voluntary movements (_____, _____)

• spinal cord: contains lower motor neurons (alpha motor neurons)

• these neurons connect to skeletal muscle

area 4, prefrontal cortex

direct motor pathways

• name the pathway

motor cortex → subcortical white matter → internal capsule → crus cerebri → basal pons → pyramids → corticospinal tracts → spinal cord ventral horn → central roots → peripheral nerves → skeletal muscle

direct motor pathways

• the _____ is responsible for thinking about moving

premotor cortex

direct motor pathways

• the _____ is responsible for initating movement (upper motor neurons)

primary motor cortex (precentral gyrus)

direct motor pathways

• internal capsule

  • _______: carries motor axons to trunk and extremities

    • continues as the crus cerebri

  • _____: carries fibers that go to brainstem

    • ______ tracts: motor cortex to skeletal muscles of head and neck to coordinate precise, voluntary movements, travel in this area

posterior limb, genu, corticonuclear

direct motor pathways

• _____: motor cortex to skeletal muscles of head and beck to coordinate precise, voluntary movement, travel in genu of internal capsule 

corticonuclear tracts (corticobulbar)

ic?

subcortical white matter

g?

genu

p?

posterior limb

direct motor pathways

• lower motor neurons = motor nuclei of cranial nerves ___, ____, ____, and ___

V, VII, IX, XIII

direct motor pathways

• discrete voluntary (somatic) movement of muscles of neck, larynx, tongue, head, and face

  • axons travel through the _______, genu of the internal capsule and crus cerebri

  • axons cross ______ at the level of the motor nucleus they innervate (lower motor neurons, no discrete decussations)

    • innervate head and neck muscles via the cranial nerves

• unlike spinal cord, innervation is often ______

corona radiata, midline, bilateral

direct motor pathways

• the crus cerebri is the continuation of the posterior limb of the ______

  • the base of the midbrain

internal capsule

cc?

crus cerebri

direct motor pathways

• ______: defines the border between the spinal cord and medulla oblongata

pyramidal decussation

pd?

pyramidal decussation (diagram)

direct motor pathways

• corticospinal tracts: 

  • _____ corticospinal tract: all fibers have crossed here

  • _____ corticospinal tract: cross in the spinal cord

lateral, ventral

direct motor pathways

• lateral corticospinal tract:

  • motor cortex control skeletal muscles on the _____ side of the body

  • precise, voluntary movements of the arms and legs

  • fibers cross at the ________

opposite, pyramidal decussation

direct motor pathways

• ventral (anterior) corticospinal tract

  • motor cortex control of skeletal muscles on _____ sides of the body

  • trunk movements (trunk moves as a unit)

  • most of the fibers cross in the spinal cord and some don’t 

both

direct motor pathways

• spinal cord ventral horn

  • corticospinal tracts synapse in the _____

  • alpha motor neurons project their axons via the _____

ventral horn, ventral roots

indirect motor pathways

• NOT part of the pyramidal process

• 3 descending pathways: _____, _____, _____

vestibulospinal tract, reticulospinal tracts, tectospinal tract

indirect motor pathways

• what organs make up the vestibulospinal tract?

vestibular nuclei, pons, and medulla

indirect motor pathways

• what organs make up the reticulospinal tract?

reticular formation found throughout the brainstem

indirect motor pathways

• what organs make up the tectospinal tract?

superior colliculi and midbrain

indirect motor pathways

• vestibulospinal tracts

  • reflexive regulation of balance and posture

  • medial vestibulospinal tracts descend _______ through cervical segments of spinal cord and influences neck musculature 

  • lateral vestibulospinal tracts descends to _______ segments of spinal cord, antigravity muscles

bilaterally, lumbar-sacral

indirect motor pathways

• reticulospinal tracts (reticular formation found throughout brainstem)

  • functions to set ________ (adjust posture) in anticipation of a movement

  • origin = reticular formation in pons and medulla

  • found at all levels of the spinal cord

muscle tone

indirect motor pathways

• tectospinal tract

  • mediates reflexive movement of head and neck in response to _____ stimuli (predominantly vision and hearing)

  • originates from the _______ (SC, midbrain) and descends through cervical levels of the spinal cord 

sensory, superior colliculus 

basal nuclei aka basal ganglia

• the basal nuclei are a collection of interconnected subcortical nuclei that function as a central link in the part of the motor system that translates the ______ to move into action

  • “______”

  • “select” desired behaviors and “inhibit” unwanted behaviors

  • while these are called the basal ganglia, we all know that ganglia are by definition OUTSIDE of the CNS

desire, organ of habit

basal nuclei

• do not make direct or indirect ______ connections with the motor neurons in the spinal cord or brain stem

  • consist of parallel, anatomical loops that originate in the cortex, pass through the basal nuclei, project to ________ then back to the cortex

synaptic, dorsal thalamus

basal nuclei

• what makes up the striatum?

caudate nucelus and putamen

basal nuclei

• what is located in the pallidum?

globus pallidus

basal nuclei

• what part of the basal nuclei is in the brain stem?

substantia nigra

basal nuclei

• what part of the basal nuclei is in the diencephalon?

subthalamic nucleus

what is c?

caudate

what is p?

putamen 

what is gp?

globus pallidus

what is i?

internal segment

what is e?

external segment

what is STn?

subthalamic nucleus

what is SN?

substantia nigra

basal ganglia

• ______ facilitates appropriate motor programs

• ______ inhibits competing motor programs

direct pathway, indirect pathway