3.) Suppose the resting membrane potential of a neuron is -70 mV and the action

Question

3.) Suppose the resting membrane potential of a neuron is -70 mV and the action

     potential threshold is -55 mV. A stimulus depolarizes the neuron to -55 mV and

     triggers an action potential. A few seconds later a second stimulus depolarizes the

     neuron to -45 mV. The second stimulus

     A.) Triggers an action potential that is larger than the first.

     B.)   Triggers an action potential that lasts longer than the first.

     C.)   Fails to fire the neuron because the Na+ channels are inactivated.

     D.)   Triggers an action potential that is identical to the first.

     E.)    Fails to fire the neuron because the threshold isn’t reached.

Activity 4

4.) Before applying TTX or lidocaine to the axon, the action potential had the same amplitude at points R1 and R2. What is the reason for this?

     A.) There are voltage-gated Na+ channels all along the axon.

     B.) The action potential is all-or none.

     C.) Action potentials regenerate themselves at each point along the axon.

     D.) All of the above.

Explanation / Answer

3. The resting memebrane potential is -70mV. When the membrane depolarizes, the action potential becomes positive. And during repolarization it go far away from resting membrane potential So, when potential is -55mV, the action potential will generate. But when the potential is -45mV, the action potential will not generate as threshold is not reached. So, the correct option is E.

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