Clinical Correlations: Parkinson's Disease

by Craig Canby, PhD

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    00:00 Now, with that basic understanding of the circuitry, we can now apply that with our understanding of of various clinical correlations. Now, I want you to think about Parkinson’s disease and what’s going on here with this circuitry. What we have in place here is a circuitry that exists between the substantia nigra and the striatum. The nigrostriatal pathway utilizes dopaminergic neurons. However, in Parkinson’s disease, we lose, there’s a loss of those neurons. As a result, the direct pathway is no longer excited. If you can’t excite the direct pathway, you cannot excite the cerebral cortex.

    00:55 In addition, this loss of dopaminergic neurons on the striatum has an effect on the indirect pathway in that it is no longer inhibited. So now, it’s going to have a more substantial influence on the cerebral cortex. As you can recall, when the indirect pathway is activated, it inhibits the cerebral cortex.

    01:20 So, that is the net effect then that an indirect pathway will inhibit those motor neurons. When those motor neurons are inhibited, then your ability to execute motor function will be diminished. Here’s a table that demonstrates the symptoms of Parkinson’s disease on the left. On the right side, we have some structural changes and causes that attend to this clinical disorder. One of the symptoms of Parkinson’s is bradykinesia or akinesia. Muscle rigidity is a symptom as well. Individuals will have a resting tremor of their hands and fingers, kind of in a pill-rolling manner. But when they move their hands and fingers, that tremor is no longer present. These individuals have difficulty initiating movements because again, there’s a lack of excitation of the motor cortex. When movements are initiated, they tend to be abnormally slow in their execution. They have a decreased facial expression, so it’s kind of a masked face expression; don’t see much emerging from their facial expressions. Now let’s take a look at the structural changes and causes of Parkinson’s. First, some of the structural changes. We have a couple.

    02:59 First is that there will be a depigmentation of the substantia nigra due to a loss of the dopaminergic neurons. You will find the presence of Lewy bodies in this disorder, histologically. This is a pathologic indicator. Then some of the causes of Parkinson’s disease include genetic factors, environmental factors, certain medications can result in Parkinson’s, MPTP, as well as vascular insult.

    About the Lecture

    The lecture Clinical Correlations: Parkinson's Disease by Craig Canby, PhD is from the course Basal Ganglia.

    Included Quiz Questions

    1. The indirect pathway is not inhibited.
    2. There is excessive stimulation of the direct pathway.
    3. Benztropine has no role in the treatment.
    4. There is decreased inhibition of the direct pathway.
    5. Acetylcholine is decreased, and dopamine is increased.
    1. It disappears with movement.
    2. It is a high-frequency tremor that appears with sustained posture.
    3. Alcohol makes it better.
    4. Movement exacerbates the tremor.
    5. It is not present at rest.
    1. Intention tremor
    2. Shuffling gait
    3. Postural instability
    4. Bradykinesia
    5. Rigidity

    Author of lecture Clinical Correlations: Parkinson's Disease

     Craig Canby, PhD

    Craig Canby, PhD

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    what an astonishing lecture!
    By Tr??ng P. on 30. July 2020 for Clinical Correlations: Parkinson's Disease

    This course helps me broaden my knowledge and I can put what I have learned into practice right after learning this lecture! Easy to grasp the ideas of the course!

    Such a good and to the point lecture
    By Shirin M. on 21. December 2019 for Clinical Correlations: Parkinson's Disease

    This lecture helped me a lot to understand what going on there!