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Upper motor neurons are any neurons that carry motor information down to the final common pathway, that is, any neurons that are not directly responsible for stimulating the target muscle. The main effector neurons for voluntary movement lie within layer V of the primary motor cortex and are called Betz cells. The cell bodies of these neurons are some of the largest in the brain, approaching nearly 100μm in diameter. These neurons connect the brain to the spinal cord, from which point nerve signals continue to the muscles by means of the lower motor neurons


Upper motor neurons travel in several pathways through the CNS:

  • tectospinal tract/colliculospinal tract: pathway from the superior colliculus to lower motor neurons, involved in involuntary adjustment of head position in response to visual information.
  • rubrospinal tract: pathway from red nucleus to lower motor neurons, involved in involuntary adjustment of arm position in response to balance information.


Upper motor neurone lesions are indicated by spasticity, exaggerated reflexes, loss of voluntary motor control and the Babinski sign.

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