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What is a motor disorder that affects the motor neurons (UMN and LMN)?
What is a disorder of movement that affects the motor unit and what part of the unit specifically?
Is it neuropathy or myopathy?
- Myasthenia gravis
- Neuromuscular junction
How common is ALS?
What is average life expectancy?
Average age of onset?
What is used to test for ALS?
- 1 in 20,000
- 3-5 years
- muscle weakness/atrophy, fasciculations, cramps, spasticity, hyperreflexia (May affect attention, memory, confrontation naming, verbal fluency)
- Babinski's sign
In ALS, there is degeneration of the ___ motor neurons in the spinal cord and _____ motor neurons in the brain.
What tracts are affected?
Corticobulbar and corticospinal
Some neurons in the CNS are spared. These are most commonly the ____ and ____.
- eye muscles
- bladder control
The exact cause of ALS is unknown. What are possible causes?
5-10% of cases are genetic
Glutamate (excitatory NT) becomes overstimulated and dies (excitotoxicity)
Autoimmune resposes (antibodies) attack its own immune system and motor neurons, impairing the function of neurons
Environmental exposure to toxic or infectious agents and dietary deficiencies
What is treatment for ALS like?
- Supportive (improve symptoms and quality of life)
- Rylusol (extends life expectancy by 1-3 mo.; primarily effective for bulbar ALS; shows to generally slow down the progression of ALS)
Myasthenia gravis is an ____ disorder. Its immune system attacks ___ receptors in the ____ ____.
- neuromuscular junction
How common is myasthenia gravis?
Which gender is it most common?
What age in most common gender?
What age in both genders?
- 20 per 100,000
- Females; 20-40
- Both: 50-70
What are symptoms of myasthenia gravis?
- Weakness/fatigue of voluntary muscles, including muscles of facial expression
- Occular symptoms (diplopia, blurred vision, ptosis/drooping
- Speech is increasingly slurred, nasal, or hoarse with ongoing speech **hallmark
- Progressive dysphagia and respiratory complications
Myasthenia gravis does not affect cardiac muscles or smooth muscles. It does affect these kinds of movements.
Facial expressions and facial movements
Pathophysiology of myasthenia gravis:
Immune system generates ___ against ACh receptors in the neuromuscular junction.
____ bind to receptors and interfere with actions of ACh at neuromuscular junction.
Secondary degenerative changes occur in junction that make transmission ___ effective.
- Antibodies (normally, ACh binds to receptors)
In normal action potentials, after successive firing we lose small amounts of NTs with no problems. Loss of ACh is problematic for myasthenia gravis.
The exact cause of myasthenia gravis is uncertain. What are possible causes?
- Thymus gland irregularities (principle organ in immune system)
- Heritable defect in immune regulation
- Viral infection (immune system mistakes ACh receptor for invading virus and attacks the receptors)
What kinds of medications are used to manage myasthenia gravis?
- Immunosuppressant agents
- Anti-cholinesterase(?) agents (keeps enzymes from degrading ACh)
Parkinson's disease is a disease of the ___ ___.
- Basal ganglia
- 1% of people over age 50-60
Symptoms of Parkinson's disease include:
- *Increased muscle tone (rigidity)
- *Slowness of movement (bradykinesia)
- *Resting tremors
- Postural instability
- Difficulty initiating movement (akinesia) (blank stare)
- Depression/cognitive deficits that are a direct result of the disease, not a reaction
- Shuffled gait
- In later stages, hallucinations and dementia are common
- *=most prominent
What kind of dysarthria is associated with Parkinson's?
In Parkinson's, neurons in the ___ ___ degenerate.
Many surviving neurons show ___ bodies, which contain alpha synuclein proteins.
*Alpha synuclein proteins normally found at the presynaptic membrane for plasticity; accumulation of this in PD results in death of neurons
Loss of dopamine-releasing axons (i.e. neurons in subtantia nigra) results in an ___ in inhibitory output from globus pallidus to the thalamus, and a ___ in excitation from the thalamus to the cortex.
Norepinephrine containing neurons also degenerate, which account for the __-___ symptoms of PD. (Give examples)
By age 45 and over, we lose 1% of dopamine containing neurons in the substantia nigra each year. Once we lose 20-30%, may show symptoms of PD.
The substantia nigra is anatomically part of the ___ but functionally part of the ___ ___
What is the net effect of loss of dopamine containing neurons in the substantia nigra?
Decrease in excitation to the cortex
What are possible causes of Parkinson's?
Early-onset: Strong genetic component, but most cases develop after age 50 w/ no family history (i.e. 95% of cases develop after age 50--no longer early onset therefore role of hereditary much less)
Viruses, mitochondrial dysfunction, and oxidative stress
Why is injecting dopamine not most efficient for PD?
dopamine cannot cross the blood-brain barrier
Which type of treatment can cross the BBB and help with PD?
- Boosts dopamine synthesis in the substantia nigra; more effective in earlier courses of the disease but doesn't stop the progression of the loss of neurons
Which disease is associated with damage to the basal ganglia, specifically the loss of neurons in the putamen and caudate nucleus, as well as the cortex?
Symptoms of Huntington's include...
- Hyperkinesia (excessive motor movements)
- Chorea (Uncontrollable movements)
- Dyskinesia (impairment of voluntary movement)
- Psychological and cognitive disorders
What are some psychological symptoms in Huntington's disease/chorea? What is the result of these symptoms appearing before motor symptoms?
- Memory impairment, hallucinations, delusions, depression, anxiety, poor judgment
- Misdiagnosis of schizophrenia
Which type of dysarthria is associated with Huntington's?
What is the incidence of Huntington's?
What age does it typically occur?
What is the average life expectancy after diagnosis?
- 1 per 10,000
- 10-15 years
What is the cause of Huntington's?
Mutation in a gene that codes for the huntingtin protein (huntingtin thought to counteract cell death...keeps cells alive)
When the huntingtin gene is affected in Huntington's disease, what is the result?
- Mutated gene has as many as 150 glutamines (amino acids) (Normal has less than or equal to 37)
- These abnormally long huntingtins aggregate, accumulate, and trigger neuronal death
Explain the role of heredity in Huntington's disease.
If a person with Huntington's disease has children, the gene will be transmitted to 50% of offspring.
What is the result of the loss of neurons in the putamen, caudate nucleus, and cortex in Huntington's? What does cortical degeneration result in?
- Loss of inhibitory output from basal ganglia to thalamus (Increase in excitation to cortex)
- Cognitive and personality disorders & ventricle enlargement
What is treatment for Huntington's?
- Medicine to control excessive movements and psychological problems
- Gene and stem cell transplantation, neurosurgery