[Biology Class Notes] on Basal Ganglia Pdf

The basal ganglia refer to a group of structures located deep within the cerebral hemispheres. These structures are a group of subcortical nuclei. The basal ganglia functions mainly include the motor control of the body. Apart from this, these also help in motor learning, emotional behaviour, etc. The basal ganglia function in the reward and reinforcement responses and actions. The basal ganglia parts include the caudate, putamen, and globus pallidus in the cerebrum, the substantia nigra in the midbrain, and the subthalamic nucleus in the diencephalon.

In this article, we will learn about the basal ganglia anatomy, pathway, connections, and components in detail. 

Basal Ganglia Anatomy 

In this section, we will learn about the basal ganglia components. Corpus Striatum is the largest part of the basal ganglia. This can also be regarded as the largest subcortical nuclei.  The Corpus Striatum consists of the Caudate and the Putamen. These two parts are divided into two halves. The Dorsal striatum controls the motor functions, whereas the ventral striatum controls the limbic action of reward and aversion.

The various basal ganglia parts comprise the internal and external segments of Globus Pallidus, Substantia Nigra (STN), and Subthalamic Nucleus (SN). The STN is the largest part of the subthalamus shaped like a lens that is formed by a cell group. The SN represents the part of the basal ganglia in the diencephalon. It is a nucleus-like structure that has reciprocal connections with other brainstem nuclei. In a nutshell, this is all about the basal ganglia anatomy.

Basal Ganglia Calcification

The calcification of the basal ganglia is a rare condition. It is caused due to the accumulation of calcium in the brain. It is known as Fahr’s syndrome. However, familial idiopathic basal ganglia calcification of primary familial brain calcification can also be called. This disease can be genetic as it takes only one faulty dominant gene to get affected. Apart from this, calcium accumulation may also occur due to infections in the parathyroid glands, which leads to basal ganglia calcification. The symptoms include clumsiness, memory loss, unsteadiness, stiff limbs, psychosis, dementia, etc. This disease can be diagnosed via MRI and CT scans. There is no proper treatment for this disease, but one can surely take proper medications to counter the symptoms. 

Basal Ganglia Pathway

The various connections of basal ganglia deal with executive functions and motor control. In this section, we will talk about the basal ganglia pathway action. Let us consider the action of picking up a pencil. Now, if you want to pick up a pencil, you need to inhibit any unnecessary movements of your arm right before picking it up. The basal ganglia play an active role in the inhibition. Also, while stretching out the arm, the basal ganglia prevent the contraction of the muscles. The connections of basal ganglia function in such a way that it inhibits contradictory movements. This results in a smooth action.

The details of this inhibitive action are not known yet. However, according to the direct model, a signal from the cortex to the basal ganglia via the caudate and putamen initiates these inhibitory actions. The signals stimulate and project into the motor cortex. As the signals pass via the subthalamic nucleus, there a considerably more suppression and contradictory actions. This happens during the indirect pathway. The proper balance between these two basal ganglia pathways leads to a smooth, fluid-like movement. 

Basal Ganglia Disorders 

There are various disorders of the basal ganglia. These mainly happen if some basal ganglia components get infected. These are mainly movement disorders associated with a variety of other motor problems. Some of such disorders include Parkinson’s and Huntington’s disease. Hemiballism and Tourette Syndrome are also caused due to the malfunction of the basal ganglia. In addition to these, the person may also experience tremors, abnormal posture, and involuntary muscle movements.  

Interesting Facts About Basal Ganglia 

• The word “basal” denotes the fact that the basal ganglia are found near the base of the brain. The use of the word “ganglia” is a bit of a misnomer, according to contemporary neuroscience conventions.

• The majority of basal ganglia nuclei have projection neurons that utilise the inhibitory neurotransmitter gamma-aminobutyric acid (GABA).

Conclusion 

The basal ganglia is an important part of the human brain. It coordinates the motor functions via the direct and indirect pathways. This enables a smooth action. Apart from this, the basal ganglia also coordinate a lot of emotional responses.