Question

How would the amplitude of the end plate potential (EPP) and the muscle AP change if you added curare (a drug that blocks nicotinic ACh receptors) to the preparation? Group of answer choices

a. The EPP amplitude would increase, no effect on AP

b. The EPP amplitude would decrease, decreased amplitude of AP

c. Curare would have no effect on the EPP amplitude or on the AP

d. Curare would abolish the EPP, but have no effect on the AP

e. Curare would abolish the EPP and abolish the AP

Answer 1

E) abolish EPP and AP.

EPP cause partial depolarization of muscle fibre, due to action of Ach on to the postsynaptic membrane in the neuromuscular junction.

When partial depolarization reaches a particular value, there is opening of voltage gated sodium channels, leading to action potential.

Curare, is a competitive blocker of Ach at Acetylcholine receptors, but it doesn't act on voltage gated sodium channels, therefore Curare blocks only EPP , but has no effect on action potential. ( Since action potential depends on summation of endplate potentials, no end plate potential means no action potential).