What is meant by crossing

Extra pyramidal motor system

Synonyms: extrapyramidal system, EPMS, EPS
English: extrapyramidal motor system, extrapyramidal system

1 definition

Under the extrapyramidal motor system, short EPMS, one understands all motor tracts that go into the spinal cord and do not belong to the pyramidal tract.

2 lanes

2.1 Rubrospinal tract

The rubrospinal tract runs from the ruber nucleus into the spinal cord. It crosses in the mesencephalon in the Forel junction on the opposite side and then runs in the lateral spinal cord to the cervical cord, according to other authors also further caudally to the sacral cord. This tract has an activating effect on the flexors and inhibiting the extensors. It is the only extrapyramidal motor system that can be involved in fine motor skills.

2.2 vestibulospinal tract

The vestibulospinal tract originates primarily from the lateral vestibular nucleus, also known as Deiter's nucleus, and runs uncrossed through the entire spinal cord. The lateral tract runs ipsilaterally and provides reflex protection in the event of a loss of balance, while the medial tract runs bilaterally and, especially in the cervical region and the shoulder, ensures that the head is aligned when the floor is moving.

It has an activating effect on the motor neurons of the extensors and inhibits those of the flexors.

2.3 Reticulospinal tract

2.3.1 Medial reticulospinal tract

The medial reticulospinal tract runs from the reticular formation of the pons and medulla oblongata into the spinal cord and runs uncrossed. It also has an activating effect on the extensors and inhibiting the flexors.

2.3.2 Lateral reticulospinal tract

This tract runs crossed and uncrossed from the medulla oblongata into the spinal cord and activates flexors and inhibits extensors.

2.4 Tectospinal tract

The tectospinal tract is a nerve fiber path that runs from the roof of the midbrain (tectum mesencephali) to the motor neurons of the spinal cord (medulla spinalis). The tectospinal tract receives its fiber tracts from the superior colliculus, crosses in the posterior decussatio tegmentalis contralateral and descends in the anterior cord of the spinal cord to the cervical cord. The fibers for the activation of contralateral and inhibition of ipsilateral neck muscles for the reflex control of head and neck movements in connection with eye movements run in the tractus tectospinalis.

2.5 olivospinal tract

The olivospinal tract leaves the lower olive complex (nuclei olivares inferiores) with its fibers and runs on the surface of the lateral cord tract of the spinal cord.

3 activation

The extrapyramidal motor system is activated on the one hand by collaterals of the pyramidal tract and on the other by premotor and supplementary motor cortex areas.

4 function

The pathways of the extrapyramidal motor system mainly activate the proximal trunk and extremity muscles. Therefore, they mainly cause mass movements in the trunk and extremities and are therefore the basis for the voluntary and fine motor movements triggered by the pyramidal trajectory. Every differentiated movement in the hand always requires a movement of the upper arm, which is carried out by the extrapyramidal motor system.