decussate

Examples of decussate in the following topics:

• Organization of Motor Neuron Pathways

  • Cortical upper motor neurons originate from Brodmann areas 1, 2, 3, 4, and 6, then descend into the posterior limb of the internal capsule, through the crus cerebri, down through the pons, and to the medullary pyramids, where about 90% of the axons cross to the contralateral side at the decussation of the pyramids.
  • The pyramidal tract is visible in red, and pyramidal decussation is labeled at lower right.

• Sensory and Motor Tracts

  • The pathway decussates at the level of the spinal cord.
  • The signals cross in the medulla oblongata, and this process is also known as decussation.

• Optic (II) Nerve

  • The optic nerve leaves the orbit, which is also known as an eye socket, via the optic canal, running posteromedially toward the optic chiasm, where there is a partial decussation (crossing) of fibers from the nasal visual fields of both eyes.

• Trochlear (IV) Nerve

  • Other than the optic nerve (cranial nerve II), it is the only cranial nerve that decussates (crosses to the other side) before innervating its target.

• Medulla Oblongata

  • This is known as the decussation of the pyramids.
  • Other fibers that originate from the anterior median fissure above the decussation of the pyramids and run laterally across the surface of the pons are known as the external arcuate fibers.

• Somatic Sensory Pathways to the Cerebellum

  • The dorsal spinocerebellar tract does not decussate, or cross sides, at all through its path.

• General Organization of the Somatosensory System

  • This neuron's ascending axons will cross, or decussate, to the opposite side of the spinal cord or brainstem and travel up the spinal cord to the brain, where most will terminate in either the thalamus or the cerebellum.