Globe pale: structure, functions and associated disorders
Although they are not as well known to most people as the cerebral lobes, the subcortical regions of the brain they fulfill equally important functions. In particular, the areas that we know as basal ganglia are fundamental for movement, among other aspects.
One of the nuclei that form the basal ganglia is the pale globe, the smallest of all. We'll see now the structure and functions of the pale globe , as well as the disorders that are related to injuries in this region, among which Parkinson's disease stands out.
What is the pale balloon?
The pale globe is also known as paleoestriado . It is a subcortical structure composed of gray matter (ie, somas of neurons, dendrites without myelin and glial cells) that develops from the diencephalon, although it is part of the telencephalon. Therefore it is located in the anterior part of the brain, on the inner side of the frontal lobe.
It is part of the extrapyramidal system , a neural network that controls and regulates involuntary movements. The extrapyramidal tracts send projections mainly to the lower motoneurons of the spinal cord that deal with movement, reflexes and posture.
This structure is more developed in primates than in other animals ; in particular, the inner region of the pale globe is found only in humans and in our closest relatives.
- Related article: "Basal ganglia: anatomy and functions"
The basal ganglia
The pale is one of the structures that constitute the basal ganglia, a set of intimately related subcortical nuclei that are located around the third ventricle. The basal ganglia perform functions mainly related to voluntary and automatic movements.
The nuclei that form the basal ganglia , in addition to the pale globe, are the following:
- Striated body: receives information from the other basal ganglia, integrates it and sends it to higher areas of the brain.
- Caudate nucleus It has connections to the frontal lobe and is involved in motivation and alarm response.
- Black substance: relevant for fine motor control; It is part of the brain reward system because it has many dopaminergic synapses.
- Núcleo accumbens: like the substantia nigra, it is part of the reinforcement system, so it has a key role in the development of addictions.
- Putamen : this structure intervenes in automated movements, especially those of the face and extremities.
- Subthalamic nucleus : connects the mesencephalon and the thalamus and regulates motor skills.
- Red substance : this region is important for coordination in general and that of the upper extremities in particular.
Structure and anatomy
The pale globe is composed mainly of very large neurons with a large number of dendritic branches. The appearance of the pale globe is peculiar because of the abundance of dendrites and their unusual length .
The name of this structure is due to the fact that it crosses many myelinated axons that connect other regions of the basal ganglia with the pale globe, giving it the whitish tone characteristic of the cerebral areas with high density of white matter.
It is usually divided the pale globe in two parts: the internal or medial and the external or lateral l . The inner pale globe receives efferents from the striatum and projects afferents to the thalamus, which will send them to the prefrontal cortex. The outer part contains GABAergic neurons and acts in conjunction with the subthalamic nucleus.
Functions of the pale globe
The main function of the pale globe is the regulation of non-conscious movements. In this sense, his role consists of modulate the excitatory impulses of the cerebellum by synapse of the neurotransmitter GABA, the most relevant inhibitory compound of the nervous system.
The joint action of the cerebellum and the pale allows the maintaining posture and performing harmonious movements . If the pale balloon does not work properly there is an impairment of gait, manual motility and many other ordinary behaviors.
This role is due mainly to the internal pale globe and its connections with superior brain structures. This region of the pale r ecibe afferents of the striatum from the basal ganglia and sends them to the thalamus, which regulates basic bodily functions such as alertness and sleep and allows sensory and motor information to reach the cortex.
The lateral part of the pale, in conjunction with the subthalamic nucleus, intervenes in the regulation of physiological rhythms of the organism, especially in relation to the rest of structures of the basal ganglia.
The lesions in the pale globe cause motor disorders since they interrupt the connections of the extrapyramidal tracts. Thus, the affectation of this structure can cause symptoms such as tremors, spasms , bradykinesia (slowness of movement), rigidity, dystonia (uncontrollable contractions), seizures or ataxia (lack of muscle coordination).
The disorder most clearly associated with damage to the pale globe is Parkinson's disease, which causes a degeneration of subcortical structures, including the basal ganglia.
Some typical symptoms of Parkinson's , such as resting tremors, muscle rigidity and postural problems, are explained by the pale and / or cerebellar lesion. However, as this disease progresses, it also causes lesions in other parts of the brain; This is the cause of the progressive cognitive deterioration found in these patients.