Understanding the Brain: The Neurobiology of Everyday Life

Final Project

Parkinson’s Disease

by Rachael Shaw

What is Parkinson’s Disease

Described by James Parkinson in 1817 Parkinson’s is characterized by degeneration of central nervous tissues, affecting the motor skills of a person, thereby impairing movements and speech.

Parkinson’s disease is a degenerative neurological disease affecting more men than women with no known cure, Parkinson’s (or idiopathic parkinsonism) has no identifiable cause. It is distinguished from secondary parkinsonism, a group of disorders similar to Parkinson’s that have known or identifiable causes.

Most people are diagnosed between 60 and 70 years old, however some people are diagnosed with early Parkinson’s such as actor Michael J. Fox at age 30.

SymptomsIn most people Parkinson’s first noticeable effects are related to movement, people may have a resting tremor(s), rigidity, balance issues, bradykinesia (slowing or loss of spontaneous/automatic movement) and/or akinesia (difficulty in initiating voluntary movements).

Some known early symptoms are rarely recognised due to their slow and gradual onset, these include expressionless face, cramped handwriting, slight shakiness and mild cognitive impairment in executive functions (eg planning, decision making and emotional control). Other early symptoms may not be seen as related to Parkinson’s for example loss of ability to sing.

Image 1

As Parkinson’s progresses other effects such as impaired cardiovascular regulation, dizziness, changes in blood pressure, digestive disorders, constipation, urinary urgency and urinary incontinence can occur.

As well as physical effects Parkinson’s can also affect thought, emotions, sleep and memory.

In later stages hallucinations and dementia can occur.

What causes Parkinson’s symptoms?

What is known is Parkinson’s first noticeable symptoms are caused by cell death in the substantia nigra (part of the basal ganglia). Dopamine is produced in the substantia nigra, cell death reduces the production of dopamine and subsequently the release of dopamine from neurons is reduced.

The substantia nigra is darkly pigmented in a normal brain, as can be seen in image 1 the substantia nigra is brownish black. In a Parkinson’s patient, the substantia nigra is barely distinguishable from the surrounding area’s indicating there are few dopamine producing cells.

Image 2

Currently the cause of Parkinson’s is unknown.

When approximately 60 to 80% of dopamine is lost, symptoms such as tremor, slowness of movement, stiffness, and balance problems occur.

It is usually when one or more of these symptoms are evident a diagnosis of Parkinson’s can be made (once any other neurological issue or disease has been excluded).Image 3

A recent hypothesis in Parkinson’s research is that two parts of the brain are involved in Parkinson’s. The substantia nigra is affected first and as Parkinson’s progresses the basal forebrain (involved in memory and attention) is affected in a similar way.

A smaller basal forebrain is believed to reduce the production of acetylcholine, (neurotransmitter with decreased concentration and function in Alzheimer's disease). This may be a partial cause of dementia and/or memory isssues in some Parkinson’s patients.

The Brains Dopamine SystemThe dopamine system is controlled by two area’s the substantia nigra and the ventral tegmental area (vtc). The vtc also produces dopamine and releases it into the frontal lobe. The vtc dopamine pathway may also play a role in Parkinson’s.

The substantia nigra manufacture and releases dopamine into the striatum. Dopamine reduces the influence of the indirect pathway, and increases the actions of the direct pathway within the basal ganglia and plays a critical role in controlling movement. A reduction in dopamine levels has a direct effect on a persons ability to execute smooth, controlled movements and on the indirect and direct pathways.

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In Parkinson’s reduced dopamine production and release result in dopamine receptors in the striatum being inadequately stimulated. When this occurs parts of the basal ganglia are under- or over-stimulated.

Issues with motion and rigidity are the result of the subthalamic nucleus becoming overactive and acting as a brake on the globus pallidus interna.

Tremors are caused when the globus pallidus interna is overstimulated resulting in an over-inhibitory effect on the thalamus, which in turn decreases the thalamus’ output. See the optional video Parkinson's Disease and Dopamine showing this process.

Brain Regions Affected

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Optional videos

http://www.youtube.com/watch?v=BarcIuIEsKk

http://www.youtube.com/watch?v=la63uShbtsc

CNN Special: Full interview with Michael J. Fox as he talks to Dr. Sanjay Gupta about Parkinson's disease and The Michael J. Fox Foundation. 40.02 minutes

Diane Sawyer's Exclusive Interview With Linda Ronstadt Rock star discusses her secret battle that silenced her singing voice.4.27 minutes

Parkinson's Disease and DopamineThe process resulting in a tremor in a series of animations. 1.22 minutes.

http://www.youtube.com/watch?v=jyBakRkzswU

Image creditsImage 1 http://careplannursing.blogspot.com.au/2012/03/parkinsons-disease-nursing-care-plan.html Image 2 http://www.nlm.nih.gov/medlineplus/ency/imagepages/19515.htm Image 3

http://www.anti-agingfirewalls.com/2012/06/30/a-stem-cell-cure-for-parkinsons-disease-so-close-and-yet-so-far-away/

Image 4 http://thesalience.wordpress.com/neuroscience/neurotransmitters/ Image 5 http://www.parkinsondisease.in/

Bibliographyhttp://www.nytimes.com/2012/11/27/health/imaging-shows-progressive-damage-by-parkinsons.html?_r=0Imaging Shows Progressive Damage by Parkinson’s, James Gorman, November 26, 2012 New York Times

http://online.wsj.com/news/articles/SB10001424052748703748904575411662795000790How Parkinson's Alters the Brain - Researchers Trace Clues to the Disease's Effects on Patients' Mental Ability, Shirley S. Wang Aug. 10, 2010 Wall Street Journal

http://www.medicalnewstoday.com/info/parkinsons-disease/ All About Parkinson’s Disease

http://biomed.brown.edu/Courses/BI108/BI108_1999_Groups/Neuroelectrodes_Team/background.html Background of Parkinson's Disease

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001762/ Parkinson's disease Paralysis agitans; Shaking palsy

http://www.parkinson.org/parkinson-s-disease.aspx

https://www.michaeljfox.org/understanding-parkinsons/index.html

http://www.parkinsons.org.au/about-ps/whatps.html

How this course allowed me to better analyse events and phenomena around

me.This course gave me the opportunity to learn and understand basic Neurobiology and neurobiological terms I have previously come across. I have been fascinated by the brain for a long time and have been unable to study in a traditional way. Thanks to courses like this one I can learn more than I ever could reading scientific journals and other materials.

I now feel able to apply knowledge from the course and better understand how my brain may be functioning or malfunctioning, particularly in relation to my sleep issues and the remnant effects of many years of drug and alcohol dependence/abuse. I have also gained a better understanding of my Dad’s Parkinson’s disease and my friends ongoing battle with anxiety and depression.

This course has given me a much greater appreciation of the complexity of the brain and the many issues that can arise when the brain incurs damage or there is a malfunction. Thanks Dr. Peggy Mason and the staff at Coursera!