Pyramidal tractsPyramidal tracts

Learning objectives:

At the end of this presentation, all the students should be able to:

The descending pathways are those routes through which motor signals are sent from brain to the body.

Anterior corticospinal tract:

The basal ganglia, brainstem, and cerebellum all receive strong motor signals from the corticospinal system every time a signal is transmitted down the spinal cord to cause a motor activity.

Damage to corticobulbar tract(upper motor neuron lesion)

  • Due to the bilateral nature of this tract, a unilateral lesion usually results in mild muscle weakness.
  • However, not all the cranial nerves receive bilateral input, and so there are a few exceptions which are;

Hypoglossal nerve :

A lesion to the upper motor neurones for CN XII will result in the deviation of the tongue to the contralateral side.

Facial nerve:

A lesion to the upper motor neurones for CN VII will result in spastic paralysis of the muscles in the
contralateral lower quadrant of the face.

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