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30 Cards in this Set
- Front
- Back
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what is the active zone of a neuromuscular junction?
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the presynaptic storage and release site for vesicles
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what is the motor end plate?
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the the postsynaptic site that contains ACh receptors
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what is the difference between a sarcolemma and a motor end plate?
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the sarcolemma is the entire plasma membrane of a muscle fiber.
the motor end plate is just the portion of the sarcolemma that creates the neuromuscular junction |
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what are the receptors of neuromuscular junctions?
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nicotinic acetylcholine receptors
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how many ACh molecules must bind to open a single nicotinic receptor?
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2
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where does the ACh bind to a nicotinic receptor?
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on each of the a-subunits
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how long does a channel stay open when ACh binds to the a-subunits?
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1 msec
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where do you find graded potentials in muscle fibers and where do you find action potentials?
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graded- NM junction
action- along the sarcolemma and through T-tubules |
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how many ACh molecules are in one vesicle?
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~10,000
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what is a MEPP
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a miniature end plate potential
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is a MEPP enought to cause an action potential?
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no
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what is a NM margin of safety?
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that one neuronal AP will release more than enough ACh to reach and surpass the muscle fiber AP threshold.
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how is the signal terminated once ACh is released in the junction?
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acetylcholinesterase quickly degrades acetylecholine. w/in 1 msec
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~ how many ACh's are degraded per sec by acetylcholinesterase?
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10,000
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which 2 transporters are required for ACh to be repackaged into synaptic vesicles?
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proton pump
ACh-H antiporter |
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what type of channels are located in the motor end plate?
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ligand gated Na+ channels
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what type of channels are located in the sarcolemma of muscle fibers?
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voltage gated Na+ and K+ channels
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what are the factors that effect the magnitude of the EPP?
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calcium channels
ACh release, breakdown, receptors |
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what is the function of non-depolarizing drugs?
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they competitively inhibit ACh receptors
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what type of drug is tubocurarine?
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a non-depolarizing drug
used to stop muscle contractions during surgery |
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what is the function of depolarizing drugs?
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induces a prolonged depolarized state that prevents action potentials from occuring
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what is succinylcholine?
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it mimics the effects of ACh, but is degraded much slower. It is a depolarizing drug
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what does the botulism toxin target?
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synaptobrevin, SNAP-25, or syntaxin and prevents the fusion of synaptic vesicles
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what type of synapses does the botulism toxin target?
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NM junctions and cholinergic synapses of the ANS
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what type of paralysis is induced by botulism toxin?
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flaccid
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what do many nerve gasses target?
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acetylcholinesterase
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what are the physical manifestations of acetylcholinesterase poisoning?
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muscle spasms followed by paraylisis
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what is the cause of Myasthenia Gravis?
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antibodies that target and block ACh receptors
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how do we treat myasthenia gravis?
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with acetylcholinesterase inhibiters
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What is the effect of neostigmine and what is it used to treat?
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acetylcholinesterase inhibiter
used for myasthenia gravis used at the end of operations to reverse the effects of non-depolarizing drugs. |
