Overview of Neuronal Connections and Normal Function
The direct pathway passes through the caudate, putamen, and globus pallidus, which are parts of the basal ganglia. It also involves the substantia nigra, a part of the midbrain. In a resting individual, a specific region of the globus pallidus, known as the internus, and a portion of the substantia nigra, known as the pars reticulata, send spontaneous inhibitory signals to the ventral anterior nucleus of the thalamus, through the release of GABA, an inhibitory neurotransmitter. Inhibition of the excitatory neurons within VA, which project to the motor regions of the cerebral cortices of the telencephalon, leads to a reduction of activity in the motor cortices and a lack of muscular action.
When the pre-frontal region of the cerebral cortex, which is generally involved in decision making and planning, determines that a particular motor activity will be executed, it sends activating signals to the motor cortices. The motor cortices send signals through the basal ganglia to refine the choice of muscles that will participate in the movement and to amplify the activity in the motor cortices that will drive the muscle contractions.
In the direct pathway, the motor cortices send activating signals to the caudate and putamen. The cells of the direct pathway in the caudate and putamen that receive these signals are inhibitory and, once they become activated, send inhibitory signals to the globus pallidus internus and substantia nigra pars reticulata. Thus, activation of the direct pathway will stop activity in the globus pallidus internus and substantia nigra pars reticulata. Before activation of the direct pathway, these two nuclei were actively sending inhibitory signals to the ventrolateral nucleus of the thalamus, which prevented the development of significant activity in the motor cerebral cortices. This behavior ceases on activation of the direct pathway. The net effect is to allow the activation of the ventrolateral nucleus of the thalamus which, in turn, sends activating signals to the motor cortices. These events amplify motor cortical activity that will eventually drive muscle contractions.
...
Read more about this topic: Direct Pathway Of Movement
Famous quotes containing the words connections, normal and/or function:
“... feminism is a political term and it must be recognized as such: it is political in women’s terms. What are these terms? Essentially it means making connections: between personal power and economic power, between domestic oppression and labor exploitation, between plants and chemicals, feelings and theories; it means making connections between our inside worlds and the outside world.”
—Anica Vesel Mander, U.S. author and feminist, and Anne Kent Rush (b. 1945)
“Like sleep disturbances, some worries at separation can be expected in the second year. If you accept this, then you will avoid reacting to this anxiety as if it’s your fault. A mother who feels guilty will appear anxious to the child, as if to affirm the child’s anxiety. By contrast, a parent who understands that separation anxiety is normal is more likely to react in a way that soothes and reassures the child.”
—Cathy Rindner Tempelsman (20th century)
“The art of living is to function in society without doing violence to one’s own needs or to the needs of others. The art of mothering is to teach the art of living to children.”
—Elaine Heffner (20th century)