Globus Pallidus: Structure, Functions And Associated Disorders

Although they are not as well known to most people as the brain lobes, the subcortical regions of the brain They perform equally important functions. Specifically, the areas we know as the basal ganglia are essential for movement, among other aspects.

One of the nuclei that make up the basal ganglia is the globus pallidus, the smallest of all. We’ll see now the structure and functions of the globus pallidus as well as disorders that are related to injuries in this region, among which Parkinson’s disease stands out.

What is the globus pallidus?

The globus pallidus is also known as the paleostriate It is a subcortical structure composed of gray matter (i.e., neuron somata, unmyelinated dendrites, 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 primarily to the lower motor neurons of the spinal cord that deal with movement, reflexes, and posture.

This structure It is more developed in primates than in other animals; In particular, the internal region of the globus pallidus is only found in humans and our closest relatives.

The basal ganglia

The pallidum is one of the structures that constitute the basal ganglia, a set of closely 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 globus pallidus, are the following:

Structure and anatomy

The globus pallidus is composed mainly of very large neurons with a large number of dendritic branches. The appearance of the globus pallidus is peculiar because of the abundance of dendrites and their unusual length

The name of this structure is due to the fact that many myelinated axons pass through it that connect other regions of the basal ganglia with the globus pallidus, giving it the whitish tone characteristic of brain areas with a high density of white matter.

The globus pallidus is usually divided into two parts: the internal or medial and the external or lateral l The internal globus pallidus receives input from the striatum and projects input to the thalamus, which sends it to the prefrontal cortex. The external part contains GABAergic neurons and acts in conjunction with the subthalamic nucleus.

Functions of the globus pallidus

The main function of the globus pallidus is the regulation of non-conscious movements. In this sense, its role consists of modulate excitatory impulses of the cerebellum through synapses of the neurotransmitter GABA, the most relevant inhibitory compound in the nervous system.

The joint action of the cerebellum and the pallidum allows the maintaining posture and performing harmonious movements If the globus pallidus does not function correctly, walking, manual motor skills and many other ordinary behaviors are affected.

This role is due above all to the internal globus pallidus and its connections with higher brain structures. This region of the pale r receives afferents from 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 pallidum, in conjunction with the subthalamic nucleus, intervenes in the regulation of physiological rhythms of the body, especially in relation to the rest of the structures of the basal ganglia.

Related disorders

Lesions in the globus pallidus cause motor disorders since they interrupt the connections of the extrapyramidal pathways. Thus, the involvement 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 globus pallidus is Parkinson’s disease, which causes degeneration of subcortical structures, including the basal ganglia.

Some typical symptoms of Parkinson’s, such as rest tremors, muscle rigidity and postural problems, are explained by damage to the pallidum and/or cerebellum. However, as this disease progresses it also causes lesions in other parts of the brain; this is the cause of the progressive cognitive impairment found in these patients.