Descending Tracts

Question 1

Rapid and skilled voluntary movements, fine motor skills, for distal musculature (limb)

Decussation: Cervicomedullary junction
Location: Lateral Column

Origin: BA 4, BA 6, BA 3,1,2
Destination: Anterior horn cells (alpha motor neurons, some gamma motor neurons) at RL VIII and IX

Answer 1

Lateral Corticospinal Tract

Question 2

Gross and postural motor function (proximal and axial musculature)
Location: Anterior Column

Decussation: spinal cord(level of destination: cervical/upper thoracic)

Origin: BA 4, BA 6, BA 3,1,2
Destination: Anterior horn cells (alpha motor neurons, some gamma motor neurons) at RL VIII and IX

Answer 2

Anterior Corticospinal Tract

Question 3

For the muscles of the face, jaw, tongue, larynx, and pharynx

Termination
Respective CN nuclei in the brainstem

Answer 3

CORTICOBULBAR TRACT

Question 4

Facilitate or inhibit the activity of alpha and gamma motor neurons. Influences voluntary and reflex activities.
[(+) descending autonomic fibers]

Pontine: Reticular form at pons
Medullary: reticular form at me

Decussation:
Pontine: mostly uncrossed
Medullary: crossed and uncrossed
Destination:
Dorsal horn, RL VIII, IX (alpha and gamma motor neurons)

Answer 4

Reticulospinal Tract

Question 5

• Influences activity of alpha and gamma motor neurons.
• Facilitates: flexor activity
• Inhibits: extensor activity

Location: Lateral Column

Origin Red nucleus at tegmentum

Decussation
Immediately at origin Destination RL VIII, IX, interneurons

Answer 5

Rubrospinal Tract

Question 6

• Influences activity of alpha and gamma motor neurons
• Facilitates: extensor activity for balance
• Inhibits: flexor activity
• Reflex: moves limb extensors – posture (anti-gravity mm)

Location: Anterior Column

Origin Lateral Vestibular nuclei at pons and medulla
Decussation: None
Destination: RL VII and VIII, interneurons to alpha and gamma motor neurons

Answer 6

Vestibulospinal Tract

Question 7

• Receives afferent info from inner ear through the CN VIII and cerebellum
• Facilitates quick movements in reaction to sudden changes in body position (e.g. falling)

Answer 7

VESTIBULAR NUCLEI

Question 8

• lesion above the midbrain
• flexed (B) UE and extended (B) LE
• RST (rubrospinal) and VST (vestibulospinal) is not affected

Answer 8

Decorticate Posturing

Question 9

• lesion at the level of midbrain
• extended (B) UE and LE
• RST is affected, VST is not

Answer 9

Decerebrate Posturing

Question 10

Influences activity of alpha and gamma motor neurons.

Location: Lateral column

Origin: Inferior olivary nucleus
Destination: RL VIII and IX

Answer 10

Olivospinal Tract

Question 11

Reflex head turning in response to auditory stimuli and reflex postural movements in response to visual stimuli

Location: Anterior column

Origin: Superior colliculi at midbrain
Decussation: Most immediately cross after origin
Destination: Anterior horn interneurons at cervical area

Answer 11

Tectospinal Tract