Parkinson's part 1 of 2 - Medical Animation by Watermark - und Video narration: Movement in the human body is modulated by the extrapyramidal system, which includes the substantia nigra, subthalamic nucleus, basal ganglia, and thalamus. The extrapyramidal system can either promote or inhibit movement. Let’s take a closer look at the key extrapyramidal structures involved in Parkinson’s disease. The basal ganglia are two large groups of nerve cells located near the base of the brain and consisting of the caudate, putamen, and globus pallidus. Together, the caudate and putamen form the striatum. The substantia nigra is a tiny structure located deep within the brain. There are actually 2 structures, but they are typically referred to as a single entity in the medical literature. Normal movement depends on adequate levels of the neurotransmitter dopamine, produced by cells in the darkly pigmented “zona compacta” of the substantia nigra, and delivered to the striatum and other parts of the brain. Because this motor pathway involves the substantia nigra and the striatum, it is known as the nigrostriatal pathway. Within the striatum, there is a delicate balance between dopamine and acetylcholine, another important neurotransmitter. In patients with Parkinson’s disease, there is massive degeneration of dopamine-producing cells in the substantia nigra. The dopamine supply to the striatum is gradually reduced. This disrupts the balance between dopamine and acetylcholine, resulting in a relative excess of acetylcholine. When 60 to 80 percent of dopamine-producing cells in the substantia nigra are damaged, the extrapyramidal system loses the ability to effectively promote movement, and the motor symptoms of Parkinson’s disease begin to appear.

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