Extrapyramidal system
The extrapyramidal system ( EPMS ) or short extrapyramidal system (EPS ) is a neuro- anatomical and physiological concept in which find all control operations of the movement ( motor function ), which do not extend over the pyramidal tract of the pyramidal system. This concept is useful only in primates, especially in humans, since the pyramidal system only with them a high level of importance and a certain dominance in the control of movement has. In other mammals, the entire motor control is practically extrapyramidal. The other vertebrates eventually have absolutely no pyramidal system.
A clear functional separation between pyramidal and extrapyramidalem system does not exist actually. Therefore, the task of the concept is repeatedly called. However, the distinction is to the understanding of neurological disorders helpful.
Design and function
The extrapyramidal system has its origins both in the motor cortex ( Brodmann's areas 6 and 8 = areae extrapyramidal ) and in numerous other core areas of the brain. Its most important components are the basal ganglia. It controls mainly the coarser appearing movements, especially of the trunk ( tonic holding and supporting motor skills ) and proximal limb muscles (so-called mass movements ) and is therefore almost the basis for the pyramidal interconnected fine motor dar. Furthermore, the EPS strongly influenced muscle tone ( rubrospinal pathways ) and also ensures the interconnection among others, the cerebellum, the optical reflex center and the equilibrium cores for the harmony of movements and posture correction. The representation of the EPS as efferent system exclusively involuntary, coarse supporting and holding movements, which is compared with the pyramidal system, is considered incorrect and obsolete. The two systems are likely to be synergistic.
The extrapyramidal system is polysynaptisch, so it has always several switch points (synapses ). The switchover takes place in the nuclei of numerous brain sections. The most important stations in the extrapyramidal system are ruber, the nucleus and the reticular formation, as only drag them directly to the upper ( first / central ) motor neuron. The most important neurotransmitter of the EPS is dopamine.
Damage the extrapyramidal system
In humans, damage to the EPS mainly due to the elimination of the inhibitory ( inhibitory ) influences on the upper motor neuron ( UMN ) in ( extrapyramidal syndrome or Extrapyramidalmotorisches syndrome ( EPMS ) ). This leads to diseases with greatly increased movements in Huntington's disease as or strongly inhibited movements such as in Parkinson's disease. In addition, inhibitory interneurons can be increased to the UMN ( hyperreflexia ) in EPS damage reflexes due to the lack of inhibitory effect. In non-primate usually occur on hemiparesis with disturbed posture and position reactions. The damage, however, lies in front of the red nucleus, hardly occur movement disorders.
Spinal cord injury with paraplegia usually attracts an injury to the extrapyramidal tracts in the spinal cord after themselves. Same time, since the pyramidal pathways are impaired, come on no muscle soothing pulses more, and the tone or the tone of reinforcing reflex arc from the spinal cord can prevail. Result is often a spasticity.