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92 Cards in this Set

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  • Back
4 Levels of the motor unit at which damage can occur:
1. Muscle
2. NMJ
3. Nerve axon
4. Motor neuron
Where are LMNs?
Spinal cord
Where are UMNs?
Where can damage affect the sensory component of a spinal reflex?
-Afferent nerve
What is a myopathic disease?
One that is caused by an intrinsic abnormality in the muscle.
What is a neuropathic disease?
A disease that causes abnormalities in peripheral nerves
Where will neuropathic diseases be more pronounced? Why?
More distally than proximally, bc the magnitude of disease is proportional to axon length.
What is a neurogenic disease?
One that interrupts normal innervation of a muscle - denervation or renervation.
What is Muscular Dystrophy?
A general category for a group of inherited chronic disorders that are myopathic.
What causes symptoms in MD?
Muscle degeneration that causes progressively worse weakness.
4 major types of MD:
1. Duchenne's MD
2. Facioscapulohumeral
3. Myotonic dystrophy
4. Limb-girdle MD
In whom is Duchenne's MD most common?
What is the characteristic feature of Duchenne's MD?
Wasting and weakness in the pelvic muscles.
What does Facioscapulohumeral MD affect?
The face and shoulder girdle
What form of MD is most common in adults?
Myotonic MD
Characteristic feature of Myotonic MD:
Inability to relax muscles after strong contraction - especially hands.
What is affected in Limb-Girdle MD?
Proximal muscles in the pelvic and shoulder girdle.
What type of inheritance is Duchenne's MD?
X-linked recessive
Does Duchenne's MD only affect males?
No; females can be carriers
What is the incidence of Duchenne's MD?
1/3500 males born
When is the onset of Duchenne's MD seen?
When boys begin to walk
What is the usual outcome of Duchenne's MD?
Death by age 20-30 due to respiratory complications.
Primary symptoms of Duchenne's MD:
Waddling, lurching gate; skeletal deformities.
2 tests for Duchenne's MD:
-Gower's maneuver
-CK serum levels high
What does Gower's maneuver test show?
Patients push up from the ground very slowly.
Why are serum CK levels high in duchenne's MD?
B/c damaged muscles leak CK into the bloodstream.
What is the Cause of Duchenne MD?
Lack of the gene for Dystrophin
What is Dystrophin?
A protein that anchors actin in the cytoskeleton to the muscle membrane.
What happens when Dystrophin is lacking?
The sarcolemma is weak and subject to shearing and tearing.
What results from shearing and tearing of the sarcolemma?
Calcium influx and muscle necrosis.
What is Becker MD and what causes it?
Very similar to Duchenne's but less severe; caused by lack of dystrophin.
How does a child with Duchenne's MD stand?
In a lordotic posture - like brenty
What is the major disease of the Neuromuscular junction?
Myasthenia gravis
2 forms of myasthenia gravis:
which is more rare?
-Autoimmune (more common)
-Congenital (more rare)
What is the problem in the autoimmune form of Myasthenia gravis?
An autoantibody to the acetylcholine receptor impairs transmission at the NMJ synapse.
What type of cholinergic receptor is on muscles?
What happens when autoantibodies bind nicotinic ACh receptors?
The Ab crosslinks receptors, and triggers internalization and degradation of the receptor.
So what 2 main things happen in myasthenia gravis?
1. Auto-Ab impairs transmission
2. Degradation reduces number of receptors
Net effect of Auto-Ab binding:
Reduced number of functional ACh receptors.
3 changes that occur when ACh receptors are decreased:
1. Decreased amplitude of EPPs
2. APs fail to fire in some muscles
3. ACh depletes w/ repeated firings
What is the net effect of reduced numbers of ACh receptors?
Skeletal muscle becomes weak and fatigued.
What is the normal turnover rate of ACh receptor degradation?
5-7 days
What is the turnover rate of ACh receptor degradation in myasthenia gravis?
2.5 days
Clinical symptoms of Myasthenia gravis:
-Drooping eyelids, slurring, difficulty breathing.
Peak age of myasthenia gravis pt
Women peak at 20-30 yrs old
Men peak at 50-70 yrs old
What gland is implicated in Myasthenia gravis?
Why the thymus?
Bc it gets a tumor and that's where the autoantibodies are made.
How does the thymus know to make an antibody to the ACh receptor?
Myoid cells in the gland have the receptor, which is antigenic.
Surgical Treatment for myasthenia gravis:
Removal of thymus - 50% of patients go into remission.
Nonsurgical treatments of myasthenia gravis:
-ACHesterase inhibitors
What is one ACHesterase inhibitor? What does it do?
Pyridostigmine - prolongs the halflife of ACh in the synaptic cleft.
Where are LMNs? (2 places)
-Spinal cord
What do LMNs do?
Directly innervate skeletal muscles
Where are UMNs?
-Higher brain regions (cortex)
What do UMNs do?
Descend and synapse on LMNs to control movement
What type of motor neurons are damaged if the symptom is Weak, Wasted, and Twitching muscles?
What type of motor neurons are damaged if the symptom is Overactive Tendon Reflexes?
Decreased muscle tone
Babinski sign
What is the Babinski sign?
Abnormal dorsiflexion in response to tickling the toes, instead of normal plantaflexion.
What disease affects both upper and lower motor neurons?
Lou Gherigs
Proper name for Lou Gehrig's:
ALS - Amyotrophic Lateral Sclerosis
What does Amyotrophic mean?
Muscle atrophy
What does lateral sclerosis mean?
Hardness of the spinal cord when the pathologist does the autopsy
Why does the spinal cord become hard in ALS?
Because of astrocyte proliferation and scarring of the spinal cord lateral columns.
What tracts are diseased in ALS?
What do the corticospinal tracts normally convey?
Info from the premotor cells of the cortex and brainstem to the spinal cord
What specific cortical cells are affected in ALS?
-Betz cells
-Pyramidal cells in layer V of motor cortex
What is usually spared in ALS?
-Ocular muscles
-Voluntary bladder sphincter muscles
-Bowel control
So what are the symptoms of ALS?
Both UMN and LMN symptoms - hyperreflexia, babinski's sign, weakness, twitching, atrophy, cramps.
What is the Pseudobulbar effect that is seen in some ALS patients?
Uncontrollable bouts of laughter, crying, or explosive speech w/out accompanying emotions.
What causes ALS?
Don't know
Where is the site of peripheral nerve disease?
-or both
Does neuropathy affect only one type of nerve fiber?
no; can affect large or small diameter fibers (Abeta or C)
Are neuropathies picky about the type of fiber they affect within a given nerve?
Yes; while they affect both motor and sensory, they'll pick one to preferentially affect.
What is a mononeuropathy?
Disease of peripheral nerve that is localized to a focal point.
What is a polyneuropathy?
Disease of peripheral nerve that is localized globally - generalized.
Important causes of peripheral neuropathy:
-Mechanical trauma
-Immune disorders
Is a peripheral neuropathy permanent or reversible?
It can be either
What is a specific immune neuropathy?
Guillian Barre syndrome
4 words to describe Guillian Barre:
PAID andy griffith and teddy r
What makes Guillain barre acute?
It has rapid onset and patients often fully recover.
What causes Guillain Barre onset?
Viral infections
What is the pathophysiology of Guillain Barre syndrome?
Inflammatory cells and antibodies attack the myelin sheath around peripheral nerves
What happens when myelin breaks down?
Axons are damaged
How are motor nerves affected when their axons are damaged?
Conduction slows or is blocked.
Symptoms of Guillain Barre:
-Crawling skin, tingling
-Hot/cold insensitivity
-Difficulty getting up
-Rapid onset of weakness and paralysis in extremities, breathing muscles, and face
What do patients with Guillain Barre LOSE?
Reflex to stretch - Areflexia
What is the cause of Guillain Barre?
Treatment for Guillain Barre: