Globus pallidus
The pale inner part of the lentiform nucleus, deep in each cerebral hemisphere, and the main output station of the basal nuclei.
At a glance
- English
- Globus pallidus
- Latin (TA2)
- Globus pallidus
- System
- Brain and spinal cord
- Region
- Head
- Side
- Paired, left and right
About the globus pallidus
The globus pallidus is a wedge of grey matter deep in the cerebral hemisphere. Together with the larger putamen, which lies lateral to it, it makes up the lentiform nucleus. Its pale look, which gives it its name, comes from the many myelinated fibres that pass through it. Medially it is bounded by the internal capsule, which separates it from the thalamus and the caudate nucleus, while a thin sheet of white matter, the lateral medullary lamina, divides it from the putamen.
A second sheet, the medial medullary lamina, splits the globus pallidus into two segments: an external, or lateral, segment and an internal, or medial, segment. The two have different roles. Both receive inhibitory GABA-releasing fibres from the striatum (the caudate nucleus and putamen), and both exchange connections with the subthalamic nucleus, which sends them excitatory fibres.
The internal segment, along with the reticular part of the substantia nigra, is the output of the basal nuclei. Its fibres leave by two routes, the ansa lenticularis, which loops round the internal capsule, and the lenticular fasciculus, which crosses it. Both join as the thalamic fasciculus and end in the ventral anterior and ventral lateral nuclei of the thalamus, which project to the motor areas of the cortex. The external segment works mainly within the indirect pathway, inhibiting the subthalamic nucleus. Through these circuits the pallidum helps to select wanted movements and suppress unwanted ones.
In Parkinson's disease the internal segment is overactive, and lesioning it (pallidotomy) or placing a deep brain stimulating electrode there can ease rigidity and drug-induced dyskinesia. Both pallida are typically damaged in carbon monoxide poisoning, and the pallidum is also affected in kernicterus and Wilson's disease.
Function and supply
- Function
- Output and relay station of the basal nuclei: the internal segment inhibits the motor thalamus, and the external segment regulates the subthalamic nucleus, so that wanted movements are released and others held back.
- Blood supply
- Lenticulostriate branches of the middle cerebral artery and the anterior choroidal artery, which supplies much of the internal segment.
Anthromica
See the globus pallidus where it really sits, with every layer of the body around it.
- Every layer, one body. Peel from muscle to bone, nerve, vessel and organ, and turn it any way.
- English and Latin. Every structure named the way your exam names it.
- Quiz until it sticks. Short drills on the structures you keep missing.
Free to start. No card.
