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What is Guillian Barre Syndrome? (4 major points)
An autoimmune, demyelinating disease that preferntially affects motor axons resulting in conduction block.
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What is conduction block?
Demyleination of the internodal spaces allows the unfocused distribtuion of the AP at areas of low sodium voltage channels. These areas fail to produce an AP.
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The standard treatment for Guillian Barre is ____ ? This treatmens stops _____ and allows__________.
Plasmophoresis. It stops the autoimmune attack and aloows the axons to be remyelinated by Schwann cells. Recovery takes about 8-12 wks.
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A muscle disease characterized by cold induced malfunctioning of the sodium gated channel.
Paramyotonia Congenita
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What is the mechanism of paramyotonia congenita?
Cold temperatures induce the depolarization of muscle fibers which remain in a refractory state for several hours and are unable to produce an AP. This can be blocked with TTX a sodium channel poison.
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Hyperkalemic Periodic Paralysis
a genetic muscle disease which causes stiffness and weakness via mutations in the Na channel. It is triggered by high levels of K.
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Myotonia Congenita
A muscle disease characterized by a hyperexcitable memebrane due to mutations in the Cl- channel. Cl- channels serve to stabilize the membrane electrical responsiveness.
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How does Botulinum Toxin disrupt neurotransmission?
BTX blocks the release of Ach from presynaptic vesicles by cleaving the SNAP 25 and synaptobrevin which are required for vesicle fusion and release.
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An autoimmune disease characterized by muscle weakeness that improves with repeated muscle contractions.
Lambert Easton Myasthenic Syndrome
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In LEMS, antibodies attack what?
the voltage gated calcium channels of the presynaptic membrane.
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Tetanic facilitation is observed in what disease. What is the mechanism?
LEMS. High frequency stimulation allows the progressive buildup of Calcium (before the removal mechanisms kick in). this increases the probability of generating an action potential
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Clinically, what is the main difference between Myasthenia Gravis and LEMS?
In MG continued activity worsens muscle weakness while in LEMS muscle weakness is reduced with activity.
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Myasthenia Gravis is an autoimmune disease where the Ab attack what?
Ach receptors on the post synaptic terminal.
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What are the effects of the binding of Ab in MG?
1)Ach is blocked from binding via direct competition for the binding site or a conformational change induced by Ab binding. 2) Ach rec. turnover is increased.3) Autoimmune compliment is activated leading to the destruction of the terminal.
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In what neuromusclular disease would the patients show normal number and frequnecy of MEPP but reduced amplitude?
Myasthenia gravis. because the presynaptic terminal is not affected only the post synaptic terminal.
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A disease characterized by muscle weakness, fatigue, and atrophy of muscles which results in the the prolongation of the EPP and multiple action potentials.
Slow channel syndrome
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A disease characterized by muscle weakness, fatigue, and atrophy of muscles which results in the the prolongation of the EPP and multiple action potentials.
Slow channel syndrome
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Slow channel syndrome (SCS) is a genetic mutation of ?? What is the consequence of this mutation?
Ach receptor channels. The channels remain open for longer than normal and are less selective. This leads to the destruction of the post synaptic terminal.
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Clinically, a reduced EPP is observed with low frequency stimluation in what conditions?
BTX, MG, LEMS, and SCS
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A sinlge stimulus on a nerve results in a prolongation of the EPP and multiple action potentials. What disease is this characateristic of?
Slow channel syndrome
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At low frequency stimulation, a patient has decremental response. At high frequency stimulation, the patient demonstrates improved synaptic tranmsimission. What disease
Labert Eaton Myasthenia Syndrome
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Name the mai component of synaptic transmission that is affected in LEMS, MG, SCS, and BTX.
LEMS: Pre Syn VG Calcium ChannelMG: Post Syn Ach receptorSCS: Post syn Ach receptor channelBTX: Pre Syn fusion proteins SNAP@% and synaptobrevin
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