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The direct pathway, sometimes known as the direct pathway of movement, is a neural pathway within the central nervous system (CNS) through the basal ganglia which facilitates the initiation and execution of voluntary movement. [1] It works in conjunction with the indirect pathway.
Indirect and direct pathways.Some neuroanatomy is excluded for simplicity.. The two major input structures of the circuit are the striatum and the subthalamic nucleus (STN). The striatum receives inputs from both the cortex and the pars compacta of the substantia nigra (SNc), while the STN only receives cortical inputs.
The indirect pathway, sometimes known as the indirect pathway of movement, is a neuronal circuit through the basal ganglia and several associated nuclei within the central nervous system (CNS) which helps to prevent unwanted muscle contractions from competing with voluntary movements. [1] It operates in conjunction with the direct pathway.
The balance of direct/indirect activity in movement is supported by evidence from neurodegenerative disorders, including Parkinson's disease (PD), which is characterized by loss of dopamine neurons projecting to the striatum, hypoactivity in direct pathway and hyperactivity in indirect pathway neurons, along with motor dysfunction. [21]
Dopaminergic pathways (dopamine pathways, dopaminergic projections) in the human brain are involved in both physiological and behavioral processes including movement, cognition, executive functions, reward, motivation, and neuroendocrine control. [1] Each pathway is a set of projection neurons, consisting of individual dopaminergic neurons.
A neural pathway connects one part of the nervous system to another using bundles of axons called tracts. The optic tract that extends from the optic nerve is an example of a neural pathway because it connects the eye to the brain; additional pathways within the brain connect to the visual cortex.
Descending tracts are pathways by which motor signals are sent from upper motor neurons in the brain to lower motor neurons which then directly innervate muscle to produce movement. The anterior corticospinal tract is usually small, varying inversely in size with the lateral corticospinal tract , which is the main part of the corticospinal tract .
The substantia nigra is located in the ventral midbrain of each hemisphere. It has two distinct parts, the pars compacta (SNc) and the pars reticulata (SNr). The pars compacta contains dopaminergic neurons from the A9 cell group that forms the nigrostriatal pathway that, by supplying dopamine to the striatum, relays information to the basal ganglia.