Spinal Tracts Simplified

Organization of Ascending and Descending Tracts in Spinal Cord

A. 2 Posterior Tracts:

The fibers of these tracts cross to the opposite side at the level of medulla:

1. Dorsal column (Cross at medulla)
   • Fasciculus gracilis
   • Fasciculus cuneatus
2. Lateral corticospinal tract (Cross at medulla)

B. 2 Lateral Tracts:

The fibers of these tracts remain on ipsilateral side:

1. Dorsal spinocerebellar tract (Do not cross)
2. Ventral spinocerebellar tract (Crosses 2 times to lie on ipsilateral side)
   • 1st crossing in the spinal cord
   • 2nd crossing in the cerebellum

C. 2 Anterior Tracts:

The fibers of these tracts cross at the level of spinal cord:

1. Anterior corticospinal tract
2. Anterior and Lateral spinothalamic tract

D. Extrapyramidal tracts:

1. Rubrospinal tract (Cross at midbrain)
2. Vestibulospinal tract: Uncrossed
3. Reticulospinal tract: Uncrossed
4. Olivospinal tract: Uncrossed

Now, look at the somatotropic arrangement of the various tracts:

• Fasciculus gracilis: lower limbs
• Fasciculus cuneatus: upper limbs
• Corticospinal tract: upper limbs medially and lower limbs laterally
• Spinothalamic tract: upper limbs medially and lower limbs laterally

Ascending tracts:

Tracts	Function
Lateral spinothalamic	Pain, Temperature
Anterior spinothalamic	Light (crude) touch
Dorsal column	Fine touch, proprioception, 2 point discrimination
Spinocerebellar	Movement and position mechanisms
Spinotectal	Afferent information for spino-visual reflexes and brings about movement of the eyes and head toward the source of the stimulation
Spinoreticular	Deep and chronic pain
Spino-olivary	Conveys information to the cerebellum from cutaneous and proprioceptive organs

Descending tracts:

Tracts	Functions
Lateral corticospinal	Fine motor (controls distal musculature) Modulation of sensory functions
Anterior corticospinal	Gross and postural motor function (proximal & axial musculature)
Rubrospinal	Motor function Facilitates the activity of flexor muscles and inhibits the activity of extensor or antigravity muscles
Vestibulospinal	Postural reflexes Facilitates the activity of extensor muscles and inhibits the activity of flexor muscles in association with the maintenance of balance
Reticulospinal	Modulation of sensory transmission Modulation of spinal reflexes Influence voluntary movements and reflex activity
Tectospinal	Reflex head turning Concerned with reflex postural movements in response to visual stimuli
Descending autonomic	Modulation of autonomic functions Controls sympathetic and parasympathetic functions
Medial longitudinal fasciculus	Coordination of head & eye movements