There is a toxin produced by a fish-hunting snail that blocks voltage-gated Ca2+

Question

There is a toxin produced by a fish-hunting snail that blocks voltage-gated Ca2+ channels in motor neurons

at the neuromuscular junction. The effect of this toxin is to paralyze the fish by:

a. preventing the influx if Ca2+ into the motor axon terminal.
b. preventing neurotransmitter release.
c. preventing the action potential from reaching the output region of the lower motor neuron. d. preventing the movement of Ca2+ across the T-tubule.
e. a and b are correct.

31. There is a type of toxin found in the liver of puffer fish that prevents the opening of voltage-gated Na+ channels in neurons. The effect of this toxin is to:

a. prevent the initiation of the action potential.
b. depolarize the membrane potential and maintain it depolarized

c. prolong the return of the membrane potential to the resting level.

d. increase the duration of the action potential
e. All except a are correct.

For a neuron or muscle cell at rest, the concentration of __ is higher __________ than ______.

a. Na+, in the extracellular space, inside the cell
b. K+, inside the cell, in the extracellular space
c. K+, in the extracellular space, inside the cell

d. Na+, inside the cell, in the extracellular space

e. a and b are correct.

Explanation / Answer

30) e.) preventing the influx if Ca2+ into the motor axon terminal and also preventing neurotransmitter release.
31) a.) prevent the initiation of the action potential. This is because the Tetrodotoxin blocks diffusion of sodium through the sodium channel, thus preventing depolarization.
32) b.) For a neuron or muscle cell at rest,the concentration of K+ is higher inside the cell than in the extracellular space

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