Extra pyramidal motor system

The human motor skills are controlled by the interaction of the two pyramidal tracts and the three extrapyramidal nerve tracts in the spinal cord. The extrapyramidal or extrapyramidal motor system In this context, is primarily responsible for involuntary and automated movements. With inflammatory diseases of the central nervous system, but also with trauma, the extrapyramidal pathways can be damaged.

What is the Extra Pyramidal Motor System?

The extrapyramidal motor or extrapyramidal system form three motor spinal cord tracts. These pathways are specifically responsible for involuntary movements of the skeletal muscles. A distinction must be made between the two pyramidal tracts, which also run through the spinal cord.

Unlike the extrapyramidal system, they serve voluntary movement. Both motor systems belong to the somatomotor system and together enable the movements and inhibitions of the skeletal muscles. An extrapyramidal system is almost exclusively found in primates. Vertebrates, for example, don't even have motor pyramidal trajectories.

The motor spinal cord system for involuntary movements of the skeletal muscles starts in humans from the motor cortex of the brain. These are the Brodmann areas six and eight, which are also known as areae extrapyramidales. The motor pathways are also connected to other core areas of the brain, for example to the so-called basal ganglia.

Anatomy & structure

Unlike the pyradmid orbits, the extrapyramidal orbits are not interconnected in a pyramid shape. The extrapyramidal system includes the tractus rubrospinalis, the tractus vestibulospinalis and the tractus reticulospinalis. The latter itself consists of the medial reticulospinal tract and the lateral reticulospinal tract.

The vestibulospinal tract extends uncrossed from the diamond pit into the spinal cord. The rubrospinal tract arises from the nucleus of the brain stem and crosses into the ventral spinal cord, where it runs downwards. The lateral reticulospinal tract of the reticulospinal tract originates in the brain area between the midbrain and the spinal cord. The medial reticulospinal tract, which runs laterally and uncrossed, comes from the so-called bridge of the central nervous system. The pathways are each equipped with several switching points in the sense of synaptic nerve endings.

Function & tasks

The task of the extrapyramidal system is to control movement. It realizes unconscious and automated movements, such as swinging your arms when you run. Even gross movements of the trunk and extremities are initiated within the structures, such as automated holding and support motor skills and mass movement. The extrapyramidal system is also responsible for maintaining unconscious muscle tension.

In this context one can speak of a network with the muscular sense. These motoric pathways are also networked with the visual system, the sense of balance and the sense of one's own spatial position. Especially the connections to the cerebellum allow the pathways to make automatic corrections to the body posture and to realize harmonious movements. The vestibulospinal tract is responsible for activating the motor neurons and inhibiting the flexors.

The rubrospinal tract, on the other hand, inhibits the extensors, activates the flexors and is the only extrapyramidal nerve involved in fine motor skills. By and large, the motor neurons of the muscles receive a command from the brain via the motor nerve tracts of the spinal cord. The motor neurons are efferent nerves that run through the entire musculature and are indispensable for movement. The connected brain regions take over the switching of the three extrapyramidal motoric pathways and plan the establishment of contact with certain motor neurons.

In the basal ganglia of the brain, for example, the selection and processing of currently required movements takes place. Among other things, it is planned to reach for an object in the field of vision. The motor pathways of the spinal cord are also involved in the inhibition of certain motor neurons, especially that of the first motor neuron. You control the arbitrary movement of the pyramidal trajectories. The exchange of information between the brain and the extrapyramidal system takes place biochemically primarily via the neurotransmitter dopamine.

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Diseases

One of the most well-known diseases of the extrapyramidal system is the extrapyramidal syndrome. In this disease, the first motor neuron is no longer inhibited. Ataxia, tremor, inhibitions to start and the tendency to fall are some of the most important symptoms of this disease. Ultimately, both strongly increased and strongly inhibited movement sequences can take place in this context. The extrapyramidal system can also be damaged in the course of the inflammatory nervous system disease multiple sclerosis.

In this case, inflammation forms in the three motor spinal cord tracts or the networked brain spheres, which, in extreme cases, can cause permanent damage after healing. When the three motor pathways become inflamed, tissue always dies. Especially if the inflammation persists too long, the body can no longer compensate for the loss of this tissue. Inflammatory damage to the extrapyramidal system usually manifests itself in a slower transmission of stimuli and the ability to react.

A loss or an increase in muscle tension can also occur in the context of damage. In addition, the postural and positional reactions are sometimes disturbed. If, instead of the extrapyramidal system, the pyramidal tracts are affected by damage, what are known as pyramidal tract signs appear. Such pyramidal trajectories correspond in particular to disturbed body reflexes, such as side-different foot reflexes or non-exhaustible reflexes of the hand.

The distinction between extrapyramidal symptoms and pyramidal symptoms can be of prognostic significance for the neurologist in connection with multiple sclerosis, for example. In the early years of the disease, signs of the pyramid orbit are said to be a rather unfavorable prognostic sign.