Nucleus · one in each half of the brain
Substantia nigra pars compacta
Also called SNc
Tightly packed dopamine cells that power smooth movement, lost in Parkinson's.
The pars compacta is the densely packed, dark part of the substantia nigra. Its dopamine cells send long fibers up to the striatum, the caudate and putamen, a hub for choosing movements. There, dopamine works like oil in an engine, letting movements start easily and flow smoothly. The death of these cells is the main cause of Parkinson's disease.
Where it is
The darker layer of the substantia nigra, deep in the midbrain on each side, lying next to its paler partner, the pars reticulata.
What it does
Dopamine supply
It releases dopamine into the caudate and putamen, the main entry stations of the basal ganglia.
Getting started
Dopamine makes it easier to begin a movement, like the first step of a walk.
Speed and vigor
It influences how quickly and forcefully you move.
Learning habits
Its signals help stamp in actions that pay off, so they become automatic.
Think of it as a small sprinkler system that keeps a whole garden watered: a few cells keeping the entire striatum supplied with dopamine.
Works with
- PutamenIts main target: dopamine here helps the putamen choose and launch body movements.
- Caudate nucleusIt also feeds the caudate, the putamen's partner in the striatum.
- Dopamine neuronIt is packed with these dopamine-making nerve cells.
- DopamineThis is the chemical messenger it makes and sends out.
- Ventral tegmental areaIts next-door neighbor makes dopamine too, but mostly for reward and motivation.
When it goes wrong
Parkinson's disease
As these cells die, the striatum runs short of dopamine, and tremor, stiffness, slowness and balance problems follow. By the time symptoms appear, many of the cells are already gone.
Treatment
Dopamine itself cannot pass from the blood into the brain, so doctors give levodopa, a building block the brain turns into dopamine. Deep brain stimulation, a kind of brain pacemaker, can also help.
For learning only, not medical advice. If you have a health concern, talk to a doctor.
Surprising facts
- People who injected a chemical called MPTP have developed Parkinson-like symptoms, because it is toxic to these dopamine cells.
Where the name comes from
Latin for "compact part", because its cells are packed tightly together.
Quick quiz
3 questions. Your answers are saved and come back in your daily review.
Which of these is a job of the pars compacta?
Show the answer
Dopamine supply. It releases dopamine into the caudate and putamen, the main entry stations of the basal ganglia.
Dopamine supply. It releases dopamine into the caudate and putamen, the main entry stations of the basal ganglia.
The pars compacta is part of which larger structure?
Show the answer
Substantia nigra. It belongs to the substantia nigra.
Substantia nigra. It belongs to the substantia nigra.
Which part fits this description? "Like a small sprinkler system that keeps a whole garden watered: a few cells keeping the entire striatum supplied with dopamine."
Show the answer
Pars compacta. It is the pars compacta. Tightly packed dopamine cells that power smooth movement, lost in Parkinson's.
Pars compacta. It is the pars compacta. Tightly packed dopamine cells that power smooth movement, lost in Parkinson's.
These parts now come back in your daily review, just before you would forget them.
Practice it and its neighbors in 3DSources
- Neuroanatomy, Substantia Nigra, StatPearls, NCBI Bookshelf
- Parkinson Disease, StatPearls, NCBI Bookshelf
- Dopamine, StatPearls, NCBI Bookshelf
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