Neuro: Pathways and Tracts

Question 1

Spinothalamic Tract

Answer 1

• Conveys Pain, Temperature and Touch for Contralateral side of body.
• Through the Pons, the STT ascends through the Ventrolateral region of the Tegmentum.
• In the midbrain, the STT merges with the ascending Medial Lemniscus.

Question 2

Medial Lemniscus

Answer 2

• Conveys Two-point Tactile Discrimination, Vibration and Proprioception for Contralateral side of the body.
• Located in Ventral tegmentum of midbrain and pons
• The tract changes from a Vertical to Horizontal orientation, but it retains a Somatotopic organization.

Question 3

Medial Longitudinal Fasciculus

Answer 3

• Conveys Ascending and Descending pathways for Coordination between cranial nerve nuclei controlling Extraocular muscles.
• Located in Dorsal aspect of Tegmentum on either side of midline
• Connects CN VI nucleus w/ Contralateral CN III nucleus to achieve Lateral Conjugate Gaze
• Lesion: MLF Syndrome (Internuclear ophthalmoplegia) - often seen in Multiple Sclerosis (MS)

Question 4

Lateral Lemniscus

Answer 4

• Conveys Auditory system fibers.
• In Pons, is located in most Lateral region of Tegmentum.
• In Midbrain, most fibers terminate in the Inferior colliculi.

Question 5

Central Tegmental Tract

Answer 5

• Key structure of the Reticular formation
• Located in Middle portion of Tegmentum
• Has fibers from Solitary tract that convey Taste sensation to Thalamus.

Question 6

Corticospinal Fibers

Answer 6

• Fibers arise from Frontal and Parietal Cerebral cortex.
• The fibers course through Crura cerebri (midbrain) and as a bundle through the Pons. (Recall that these fibers form the Pyramids when they course through Medulla)
• Project to Spinal cord via Pyramids.

Question 7

Corticobulbar Fibers

Answer 7

• Arise from Motor cortex (the portion controlling Face and Head muscles).
• Synapse directly on Cranial motor neurons of
• *CN V, CN VII, CN XII** and on certain cell groups of reticular formation.

Question 8

Corticopontine Fibers

Answer 8

1. Arise from Four lobes (Frontal, Parietal, Occipital and Temporal).
2. Descend Ipsilaterally with the Corticobulbar and Corticospinal fibers and synapse on Pontine nuclei.

Question 9

Descending Autonomic Fibers

Answer 9

1. Arise mostly from Hypothalamus.
2. Descend in the Lateral region of the Brainstem.
3. Make connections with Preganglionic Parasympathetic and Sympathetic Neurons.