Globus pallidus

Definition

The globus pallidus is a critical structure within the basal ganglia, playing a significant role in the regulation of voluntary movement. It is divided into two segments: the external segment (GPe) and the internal segment (GPi), each contributing to the modulation of motor commands sent from the cortex to the thalamus. By processing and filtering information from various regions, the globus pallidus helps in action selection, ensuring that appropriate movements are executed while suppressing unwanted ones.

5 Must Know Facts For Your Next Test

1. The globus pallidus has an essential role in regulating muscle tone and coordinating smooth movements by influencing motor pathways.
2. It acts as an output station of the basal ganglia, sending inhibitory signals to the thalamus, which then relays information to the motor cortex.
3. The balance between the activities of the internal and external segments of the globus pallidus is crucial for normal motor function; dysfunction can lead to movement disorders.
4. Abnormalities in globus pallidus activity are associated with neurological conditions such as Parkinson's disease and Huntington's disease.
5. Involvement of the globus pallidus in action selection allows for adaptive changes in behavior based on environmental cues and prior experiences.

Review Questions

• How does the globus pallidus contribute to voluntary movement control?
  • The globus pallidus contributes to voluntary movement control by processing motor information and regulating signals sent from the basal ganglia to the thalamus. It uses inhibitory neurotransmission to influence thalamic activity, which in turn affects motor commands relayed to the motor cortex. By modulating these signals, it ensures that appropriate movements are initiated while suppressing unwanted ones.
• Discuss how abnormalities in the globus pallidus can lead to movement disorders.
  • Abnormalities in the globus pallidus can disrupt its normal function in regulating movement, leading to disorders such as Parkinson's disease and Huntington's disease. In Parkinson's disease, degeneration of dopaminergic neurons affects communication between the striatum and globus pallidus, resulting in increased inhibitory output that causes rigidity and bradykinesia. Conversely, in Huntington's disease, there is a loss of inhibitory neurons leading to overactivity of the globus pallidus, which manifests as chorea or involuntary movements.
• Evaluate the role of the globus pallidus in action selection and how it interacts with other structures in the basal ganglia.
  • The globus pallidus plays a pivotal role in action selection by filtering and prioritizing motor commands generated by other structures in the basal ganglia. It integrates inputs from the striatum and substantia nigra, balancing excitatory and inhibitory signals to determine which actions are executed. This dynamic interaction ensures that appropriate responses are chosen based on context and past experiences while inhibiting competing actions, facilitating smooth and coordinated movements.

Related terms

Basal Ganglia: A group of nuclei in the brain associated with motor control, as well as cognitive and emotional functions.

Substantia Nigra: A component of the basal ganglia involved in reward, addiction, and movement, containing dopaminergic neurons that project to the striatum.

Striatum:

A major input region of the basal ganglia, which receives signals from the cortex and sends output to the globus pallidus and substantia nigra.