Nucleus · one in each half of the brain
External globus pallidus (GPe)
Also called GPe, Lateral globus pallidus
A busy middle station on the "no-go" pathway that helps hold back unwanted moves.
The external segment is the outer part of the pale globe. It is a key stop on the indirect, "no-go" pathway: when the striatum quiets it, the subthalamic nucleus is freed to press harder on the brake. It is tightly linked with the subthalamic nucleus, and in Parkinson's disease the balance between the two goes wrong.
Where it is
The outer layer of the globus pallidus, between the putamen and the internal segment.
What it does
Part of the "no-go" route
When the striatum quiets the GPe, the GPe stops holding back the subthalamic nucleus, which then presses the output brake harder.
A close partner
It keeps the subthalamic nucleus in check with a steady stream of calming signals.
Keeping the system balanced
It sends calming GABA signals to other parts of the basal ganglia, including the subthalamic nucleus and the GPi, helping keep the whole system steady.
Think of it as a middle manager who can calm the whole office, and whose silence lets the strict supervisor step in.
Works with
- PutamenSends it the "no-go" signals of the indirect pathway.
- Subthalamic nucleusIts closest partner, which it keeps in check with calming signals.
- Internal globus pallidus (GPi)Its inner neighbor, which it helps calm.
- Substantia nigra pars reticulataThe other output station, which it influences through the subthalamic nucleus.
- GABAThe calming chemical it uses to send its messages.
When it goes wrong
Parkinson's disease
In Parkinson's disease, the GPe is held back too much. That frees the subthalamic nucleus to fire too much, which adds to stiffness and slowness.
Huntington's disease
Early in the illness, the striatal cells that send messages to the GPe are among the first lost, which tilts the balance toward extra, unwanted movements.
For learning only, not medical advice. If you have a health concern, talk to a doctor.
Surprising facts
- Many of its cells fire in a steady stream even at rest.
Where the name comes from
"External" because it sits on the outer side of the globus pallidus, closer to the putamen.
Quick quiz
3 questions. Your answers are saved and come back in your daily review.
Which of these is a job of the external segment (GPe)?
Show the answer
Part of the "no-go" route. When the striatum quiets the GPe, the GPe stops holding back the subthalamic nucleus, which then presses the output brake harder.
Part of the "no-go" route. When the striatum quiets the GPe, the GPe stops holding back the subthalamic nucleus, which then presses the output brake harder.
The external segment (GPe) is part of which larger structure?
Show the answer
Globus pallidus. It belongs to the globus pallidus.
Globus pallidus. It belongs to the globus pallidus.
Which part fits this description? "Like a middle manager who can calm the whole office, and whose silence lets the strict supervisor step in."
Show the answer
External segment (GPe). It is the external segment (GPe). A busy middle station on the "no-go" pathway that helps hold back unwanted moves.
External segment (GPe). It is the external segment (GPe). A busy middle station on the "no-go" pathway that helps hold back unwanted moves.
These parts now come back in your daily review, just before you would forget them.
Practice it and its neighbors in 3DSources
- Circuits within the Basal Ganglia System, Neuroscience (Purves et al.), NCBI Bookshelf
- Neuroanatomy, Globus Pallidus, StatPearls, NCBI Bookshelf
- 10.3 Our Brain Gets Involved - Responsibilities of Upper Motor Systems, OpenStax, Introduction to Behavioral Neuroscience
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Explore the external globus pallidus (GPe) in 3D
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