TBR Test 2 Muscle Contraction

[Chocolatebear89]

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142.

Ethylenediaminetetraacetic acid (EDTA), shown in the diagram below, is added to the medium surrounding an isolated neuromuscular junction taken from a frog's leg. An electrical stimulus is then administered to the nerve. What changes in muscle contraction should be observed?

A. The strength of muscle contraction increases.
B. The frequency of muscle contraction increases.
C. The muscle exhibits tetany.
D. The muscle does not contract.

I'm not sure how to find the answer to this question.

 

[Isoprop]

I haven't looked at Bio in a long time, but EDTA is a chelating agent that will bind to Ca2+. So I'm guessing D.

 

[Charles_Carmichael]

Yup, EDTA sequesters Ca2+ ions. The only answer choice that would make sense is D. This is because at the synapse, in order for the neurotransmitter to be secreted, there needs to be an influx of Ca2+ into the neuron to stimulate the fusion of docked vesicles containing neurotransmitter (ACh in this case). When Ca2+ is sequestered, there's no Ca2+ influx and thus, no secretion of ACh. This means that the muscle is not stimulated to contract.

 

[2010premed]

Also, the first three choices have to do with the refractory period