The Physiology of a Neurodegenerative Disease: Huntington’s Disease
Following the American Psychological Association’s Guidelines
Colorado Christian University
The patient, Gerald, has been diagnosed with Huntington’s Disease (HD). His niece Amanda is a science student currently in grad school. Amanda is trying to get more information regarding HD and its symptoms and treatment options. Gerald is exhibiting the following symptoms:
* Twitchy movements
* Odd facial expressions
* Difficulty balancing/walking
Amanda has reached out to some of her classmates that are further along in their schooling then herself for more information.
As Amanda learns more about her Uncles condition, she realizes that HD is a serious disease and has no known cure. Her friends comfort her and inform her that Gerald will need increasingly more help and compassion as he works through this disease. ...view middle of the document...
Difficulty organizing, prioritizing or focusing on tasks
g. Lack of flexibility or the tendency to get stuck on a thought, behavior or action (perseveration)
h. Lack of impulse control that can result in outbursts, acting without thinking and sexual promiscuity
i. Lack of awareness of one's own behaviors and abilities
j. Slowness in processing thoughts or ''finding'' words
k. Difficulty in learning new information
l. Feelings of irritability, sadness or apathy
m. Social withdrawal
o. Fatigue and loss of energy
p. Frequent thoughts of death, dying or suicide
q. Parkinson's occurs as result of a loss of nerve cells in the part of the brain known as the substantia nigra. These cells are in charge of manufacturing a chemical known as dopamine, which permits messages to be sent to the parts of the brain that conduct movement. With the exhaustion of dopamine-making cells, these parts of the brain are incapable of function normally.
1. What is the effect of GABA (gamma amino-butyric acid) on the nervous system? What does this do to membrane potential?
a. GABA acts at inhibitory synapses in the brain by attaching to specific membrane receptors in the plasma membrane. It causes a negative change in membrane potential.
2. How would this change in membrane potential affect action potentials and muscle movement?
b. This would cause the action potential threshold to be reached much easier, causing muscle contraction to occur at times when it normally would not (twitching).
3. Would the loss of striatal neurons result in higher or lower GABA levels? Why might this lead to the symptoms observed with HD?
c. Lower, with lower GABA levels, the membrane potential is thrown off and leads to the observed symptoms.
Marieb and Hoehn, Human Anatomy & Physiology, Tenth Edition, Pearson, 2010/2016
National Institute of Neurological Disorders and Stroke, Nov 4, 2008
Nance, M.A. 2007. Comprehensive care in Huntington’s disease: A physician’s perspective. Brain Research Bulletin 72:175-178
Shoulson, I., and F. Fahn. 1979. Huntington disease: Clinical care and evaluation. Neurology 29(I):1–3.
New England Journal of Medicine 1990; 323:682September 6, 1990