In human anatomy

Human anatomy

Human anatomy is primarily the scientific study of the morphology of the human body. Anatomy is subdivided into gross anatomy and microscopic anatomy. Gross anatomy is the study of anatomical structures that can be seen by the naked eye...

, the extrapyramidal system is a neural network

Neural network

The term neural network was traditionally used to refer to a network or circuit of biological neurons. The modern usage of the term often refers to artificial neural networks, which are composed of artificial neurons or nodes...

 located in the brain

Human brain

The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...

 that is part of the motor system

Motor system

The motor system is the part of the central nervous system that is involved with movement. It consists of the pyramidal and extrapyramidal system....

 involved in the coordination of movement. The system is called "extrapyramidal" to distinguish it from the tracts of the motor cortex that reach their targets by traveling through the "pyramids

Pyramid of medulla oblongata

The anterior or ventral portion of the medulla oblongata is named the pyramid and lies between the anterior median fissure and the antero-lateral sulcus....

" of the medulla

Medulla oblongata

The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...

. The pyramidal pathways (corticospinal and some corticobulbar tracts) may directly innervate motor neurons of the spinal cord or brainstem (anterior (ventral) horn cells

Anterior horn (spinal cord)

The anterior horn of the spinal cord is the ventral grey matter section of the spinal cord. The anterior horn contains motor neurons that affect the axial muscles while the posterior horn receives information regarding touch and sensation...

 or certain cranial nerve nuclei), whereas the extrapyramidal system centers around the modulation and regulation (indirect control) of anterior (ventral) horn cells.

Extrapyramidal tracts are chiefly found in the reticular formation

Reticular formation

The reticular formation is a part of the brain that is involved in actions such as awaking/sleeping cycle, and filtering incoming stimuli to discriminate irrelevant background stimuli...

 of the pons

Pons

The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...

 and medulla

Medulla

Medulla refers to the middle of something and derives from the Latin word for marrow. Its anatomical uses include:* Medulla oblongata, a part of the brain stem* Renal medulla, a part of the kidney* Adrenal medulla, a part of the adrenal gland...

, and target neurons in the spinal cord involved in reflexes, locomotion, complex movements, and postural control. These tracts are in turn modulated by various parts of the central nervous system, including the nigrostriatal pathway

Nigrostriatal pathway

The nigrostriatal pathway is a neural pathway that connects the substantia nigra with the striatum. It is one of the four major dopamine pathways in the brain, and is particularly involved in the production of movement, as part of a system called the basal ganglia motor loop.Loss of dopamine...

, the basal ganglia

Basal ganglia

The basal ganglia are a group of nuclei of varied origin in the brains of vertebrates that act as a cohesive functional unit. They are situated at the base of the forebrain and are strongly connected with the cerebral cortex, thalamus and other brain areas...

, the cerebellum

Cerebellum

The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...

, the vestibular nuclei

Vestibular nuclei

The vestibular nuclei are the cranial nuclei for the vestibular nerve.In Terminologia Anatomica they are grouped in both the pons and medulla.-Subnuclei:There are 4 subnuclei; they are situated at the floor of the fourth ventricle....

, and different sensory areas of the cerebral cortex

Cerebral cortex

The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...

. All of these regulatory components can be considered part of the extrapyramidal system, in that they modulate motor activity without directly innervating motor neurons.

See also

• List of regions in the human brain
• Extrapyramidal symptoms
  Extrapyramidal symptoms
  The extrapyramidal system can be affected in a number of ways, which are revealed in a range of extrapyramidal symptoms , also known as extrapyramidal side-effects , such as akinesia and akathisia .Extrapyramidal symptoms are various movement disorders such as acute dystonic reactions,...
  
  
• Rabbit syndrome
  Rabbit syndrome
  Rabbit syndrome is a rare form of extrapyramidal side effect of antipsychotic drugs in which perioral tremors occur at a rate of 5 Hz. Rabbit syndrome is characterized by involuntary, fine, rhythmic motions of the mouth along a vertical plane, without involvement of the tongue...
  
  , a rare extrapyramidal side effect