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jhow2319 jhow2319
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Posts: 3
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9 years ago
Patient A was administered a compound that blocks voltage gated calcium channels.  Patient B was administered strychnine, which inhibits acetylcholinesterase.  Patient C was administered curare, which binds to (and blocks) ligand gated sodium channels.  Predict the consequences of each of these situations with regard to what is happening at the neuromuscular junction and subsequent skeletal muscle contraction, not cardiac, or smooth.

So far this is what I have, I wanted to make sure I had everything correct before submitting this assignment! Any help or suggestions would be great:

Patient A-

At the muscular level, lack of calcium/no calcium results in troponin not binding to calcium, tropomyosin is still in the way and not shifted for active site on actin, the myosin head cannot bind with troponin to form cross bridges that ultimately perform the power stroke resulting in the contraction phase of a muscle twitch.  At the neuromuscular junction, if calcium channels are blocked, the result would be a lack of voltage gate Ca2+ channels on membrane at terminal, which leads to no neurotransmitter ACH being released from the vesicles into the synaptic cleft. 

Patient B-
Patient B was administered strychnine, which inhibits acetlycholinesterase. Without ACH-ase working properly, the neurotransmitter acetylcholine would not be broken down and taken back up by the terminal end of the axon to be recycled. If ACH is not being broken down, it would keep binding with ligand gated receptor proteins, which cause Na+ channels to open, causing depolarization of muscle membrane. ACH-ase being inhibited would ultimately lead to a constant contraction at the muscle.

Patient C-

Patient C was administered curare, which blocks ligand gated Na’ channels. This mechanism may contribute to the reduction in muscle excitability. Excitability is how the muscle responds to stimuli, or in this case the action potential from the neuron. With no Na’ channels being available, the depolarization of the post-synaptic membrane at the synapse would not occur. Without depolarization the action potential cannot travel down  the T-tubule, calcium would not be released, resulting in no muscle contraction. Curare affects the stimulus, which normally leads to the initiation of the muscle action potential.

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doubleudoubleu
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Posts: 437
9 years ago
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