CH 6 Corticospinal tract and other motor pathways

Lateral Corticospinal Tract: Function and Name/Level of Decussation

• Function: Motor

• Name of Decussation: Pyramidal Decussation

• Level of Decussation: Cervicomedullary Junction

Posterior Column - Medial Meniscal Pathway: Function and Name/Level of Decussation

• Function: Sensory (Vibration, Jt position, Fine touch)

• Name of Decussation: Internal Arcuate Fibers

• Level of Decussation: Lower Medulla

Anterolateral Pathway: Function and Name/Level of Decussation

• Function: Sensory (Pain, Temp, Crude Touch)

• Name of Decussation: Anterior Commissure

• Location of Decussation: Spinal Cord

Primary Motor Cortex Broca's area number

Area 4

PMC controls what?

Movement on the contralateral side of the body

Lesion on PMC (Area 4) affects what?

Motor deficits in contralateral side of body

Supplementary Motor Area and Premotor Cortex Broca's area number

Both Area 6

Where is the Supplementary Motor Area and Premotor Cortex located?

Anterior to PMC

What is the Supplementary Motor Area and Premotor Cortex involved in? What does it project to?

Higher order movement planning and project to Primary Motor Cortex

Lesions in the Supplementary Motor Area and Premotor Cortex cause what?

Deficits in movement planning

Reciprocal connections for the Supplementary Motor Area and Premotor Cortex also exist where?

Between motor and sensory areas

Motor and sensory pathways maintain what along their entire length?

Rough Somatotopic Organization along their entire length

The legs are ____ to the arms and what does LE = ?

• LATERAL

• Lower Extremity = Lateral

The legs are lateral to the arms w what 2 exceptions?

• Primary Motor and Primary Somatosensory Cotrex

• Dorsal (Posterior) Columns

What are the 2 Contents of Gray Matter?

• Neuron Cell Bodies

• Laminae

What are Laminae?

Functional groups of nuclei

2 Contents of Ventral/Anterior Horn

• Motor Nuclei (Motor Neuron Pools (MNP))

  • Laminae

What are the Laminae contained in the Ventral/Anterior Horn? And what do they do?

Laminae VIII-IX (8-9) >> Outgoing skeletal muscle innervation

Contents of Dorsal/Posterior Horn

• Sensory Nuclei

  • Laminae

What are the Laminae contained in the Dorsal/Posterior Horn? And what do they do?

Laminae I-VI (1-6) >> Incoming sensory information

What are the 2 contents in the Intermediate Zone?

• Laminae VII (7)

• Laminae X (10)

Laminae 7 function

Visceral function

Laminae X Location and Function

• Location: Gray Commissure

• Function: Axons cross to other side of SC

What type of axons are in White matter?

Myelinated Axons

White Matter are what 2 types of Axons that surrounds what?

White matter are ascending and descending axons that surround gray matter

What does White Matter form?

Motor and sensory tracts/fasciculi

What is the Dorsolateral Sulcus an entry point of?

Sensory Axons

White matter: which commissure is it consisted of and its a decussation for which axons?

• anterior commissure

• Decussation of spinothalamic tract axons

Cervical Enlargement and Lumbosacral Enlargement SC Level

• Cervical: C3-T1

• Lumbosacral: L1-S2

In regards to the 2 enlargements, more motor nuclei in the ventral horns are innervations for what?

Arms and Legs

Does the Cervical levels have MORE OR LESS white matter than lumbosacral levels?

More bitch

Where has the Ascending Fibers in Cervical level entered?

Spinal cord

What happens to the Descending fibers in the Cervical Levels?

Not yet reached target motor nuclei

Anterior Spinal Artery location:

Ventral, lateral 2/3 of SC

Posterior Spinal Artery location:

Dorsal, midline 1/3 of SC

What does the Anterior and Posterior Spinal Artery form around the SC?

Spinal Artery Plexus

What other artery also assist w supplying the SC inferiorly?

Several radicular arteries (Off aorta)

What does Basal Ganglia and Cerebellum provide? Do they have direct connections with everything?

• Major, indirect influence on the motor system

• No, they have NO direct connection to LMN

Basal Ganglia and Cerebellum function: what refines motor output? What do they receive and for about what?

• Feedback systems that refine motor output

• Receive major inputs from motor cortex about planned movement

Basal Ganglia and Cerebellum function: what do they send? How do they adjust activity?

• Send outputs through thalamus to influence motor cortex

• Adjust activity in the descending motor pathways via these feedback loops

What are UMN?

Motor neuron that projects from cerebral cortex down to spinal cord (or brainstem) to synapse onto LMN

What are LMN?

Motor neuron located in anterior horn of gray matter of spinal cord (or brainstem) that projects out to striated muscle

What are LMN composed of? And how big are they?

Alpha motor neurons >> Largest neurons in the SC

What are Gamma Motor Neurons associated w?

Muscle spindle in order to increase its sensitivity to stretch (don’t confuse it with the LMN)

What are tracts generally named according to?

Origin and Termination

Tract Naming Ex: Corticospinal Tract: where does it originate/terminate from? Where does it descend from and why?

• Originates in Cortex and terminates in Spinal Cord

• Descending motor tracts from the cortex (UMN) influence motor outputs by synapsing on LMNs

Regarding lateral and medial motor pathways, Descending motor pathways/systems are categorized based on what?

Location in the SC

Where are Lateral Motor Pathways located? And what do they do?

Located in the lateral portion of the SC to synapse on lateral motor nuclei in the anterior horn (distal musculature )

Where are Medial Motor Pathways located?

Located in medial of SC to synapse on medial motor nuclei in the anterior horn (proximal musculature)

What are the 2 Lateral Motor Pathways?

• Lateral Cotricospinal tract

• Rubrospinal Tract

What are the 4 Medial Motor Pathways?

• Anterior Corticospinal Tract

• Vestibulospinal Tract

• Reticulospinal Tract

• Tectospinal Tract

Lateral Corticospinal Tract: Origin, Site of Decussation, Level of Termination, Function

• Origin: Primary Motor Cortex and other frontal and parietal areas

• Site of Decussation: Pyramidal decussation, at the cervicomedullary junction

• Level of Termination: Entire Spinal Cord (Cervical and Lumbosacral Enlargement)

• Function: Movement of limbs

Rubrospinal Tract: Origin, Site of Decussation, Level of Termination, Function

• Origin: Red Nucleus, Magnocellular Division

• Site of Decussation: Ventral segmental decussation in midbrain

• Level of Termination: Spinal Cord

• Function: Movement of Contralateral Limbs