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===Extrapyramidal System===

===Extrapyramidal System===

[[Image:Extrapyramidal system.jpg|thumb|right|150px|Extrapyramidal System © Sarah Hamilton]]

[[Image:Extrapyramidal system.jpg|thumb|right|150px|Extrapyramidal System © Sarah Hamilton]]

 

The extrapyramidal system represents part of the motor pathway system that has synapses within the brain stem which is in contrast to those of the pyramidal system. The extrapyramidal tract is distinguishable from the pyramidal system as tracts do not run within the pyramids of the [[Hindbrain_-_Anatomy_%26_Physiology#Medulla_Oblongata|medulla oblongata]] and instead run outside. This pathway contains various multisynaptic pathways that relay within several nuclei in the brain. These nuclei are dispersed from the telencephalon to the [[Hindbrain - Anatomy & Physiology#Medulla Oblongata|medulla oblongata]] and may be visible grossly. Other parts of the extrapyramidal tract take origin from the tectum and reticular formation. These synapses within the brain stem make it possible for the for motor neurone signals to be influenced as they enter the ventral horn of the spinal cord. The [[Hindbrain_-_Anatomy_%26_Physiology#Cerebellum_Structure_.26_Function|cerebellum]] utilises this influence to ensure that movements are smooth and coordinated.  

The extrapyramidal system represents part of the motor pathways that has synapses within the brain stem which is in contrast to those of the pyramidal system. The extrapyramidal tract is distinguishable from the pyramidal system as tracts do not run within the pyramids of the [[Hindbrain_-_Anatomy_%26_Physiology#Medulla_Oblongata|medulla oblongata]] and instead run outside. These synapses within the brain stem make it possible for the for motor neurone signals to be influenced as they enter the ventral horn of the spinal cord. The [[Hindbrain_-_Anatomy_%26_Physiology#Cerebellum_Structure_.26_Function|cerebellum]] utilises this influence to ensure that movements are smooth and coordinated.  

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It is thought that the extrapyramidal system represents an earlier evolutionary development than the pyramidal system and therefore  is more often a feature of animals less able to perform complex movements. It is the most important system in domestic species.

There are a number of neurones involved in modifying the neuronal signals in the exrtapyramidal tract. These include the neurones then relay within nuclei which include the red nucleus, the substantia nigra, the caudate nucleus, the subthalamic nuclei and the olive in the [[Hindbrain - Anatomy & Physiology#Medulla Oblongata|medulla oblongata]]. The [[Sensory_Pathways_-_Anatomy_%26_Physiology#Ascending_Reticular_Formation|reticular formation]] is also involved in the extrapyramidal pathway. Neurones that relay in the red nucleus and reticular formation relay directly onto lower motor neurons whilst others relay to other nuclei. The main descending motor tracts from the red nucleus and the reticular formation are the '''rubrospinal tracts''', the '''reticospinal tract''', the vestibulospinal tract''' and the '''tectospinal tract'''. The rubrospinal tract is the important in carnivores and ungulates as it modulates pattern generators in the [[Spinal Cord - Anatomy & Physiology|spinal cord]].

 

*More complex than the pyramidal system as involves various multisynaptic pathways that relay within several nuclei in the brain.

**Nuclei are dispersed from the telencephalon to the [[Hindbrain - Anatomy & Physiology#Medulla Oblongata|medulla oblongata]] and may be visible grossly.

The extrapyramidal tract is responsible for the control of larger muscles and also groups of muscles. This tract constitutes a major part of the coordination system in which groups of muscles are used to maintain posture and smooth movements during locomotion. These types of movements do not require the same level of concious input or concentration as those of the pyramidal tract. It is thought that the extrapyramidal system represents an earlier evolutionary development than the pyramidal system and therefore  is more often a feature of animals less able to perform complex movements. It is the most important system in domestic species.

**Neurones then relay within nuclei which include:

***Red nucleus

***Substantia nigra

***Caudate nucleus

***Subthalamic nuclei

***Olive in the [[Hindbrain - Anatomy & Physiology#Medulla Oblongata|medulla oblongata]]

***Reticular formation

**Neurones that relay in the red nucleus and reticular formation relay directly onto LMNs, others relay to other nuclei.

* The main descending motor tracts from these two nuclei are:

** Rubrospinal tract - important in carnivores and ungulates. Modulates pattern generators in the [[Spinal Cord - Anatomy & Physiology|spinal cord]].

** Reticospinal tract  

** Vestibulospinal tract  

** Tectospinal tract

==Links==

==Links==