Question

an i dividual has just ingested a poison of unknown properties. His muscle, including the diaphtagm, begin to contract. However, they will contract when stimulates with an external electrode. What is the poison doing to the individual?

A) preventing release of calcium

B) preventing ACH from binding to receptors on the sarcolemma

C) preventing degradation of acetylcholinestarase

D) preventing binding of ATP

Answer 1

Answer

The given poison affects the muscle function and leads to increased contraction.

normaly muscle contraction occurs when an motor impulse reaches through a nerve axon and when the impulse are reaching the neuromuscular junction , there will be release some chemical messanger known as neurotransmitters from the presynaptic neuronal end into the synaptic cleft .( acetylcholine is one example . ) this process needs the entry of calcium into the presynaptic neurons through chanels. oncce the neurotransmitters are in the cleft , they will bind with its specific receptors present in the postsynaptic membrane like sarcolemma, action potential are generated by entry of sodium ions and it will be transfered into the muscle T tubules, which casuse opening of ryanodine receptors in sarcoplasmic reticulam and efflux of more calcium into sarcoplasm, this calcium is needed for muscle contraction by binds with troponin. normaly the action of acetylcholine in the neuromuscular junction is short lived , it will be degraded easily by some enzyme known as acetylcholinesterase . so that continued action of acetylcholine won't occur .

here the poison act like acetylcholin and preventing the binding of acetylcholine to the sarcolemma, and cause depolarisation of  sarcolemma , these substance will degrades slower than normal acetylcholine , they produces persistent depolarization of muscle membrane and leads to continued muscle contraction initialy follwed by paralysis.