Question

The action potential is around -70 mC. a. True b. False

Answer 1

The claim that the action potential is around -70 mC is false; action potential involves voltage changes in millivolts (mV), not charge in Coulombs. The generation of an action potential requires depolarization of approximately +15 mV, electric-field lines from a positive point charge do indeed radiate outward, and the relative refractory period voltage is near -45 or -80 mV.

Step-by-step explanation:

The statement that action potential is around -70 mC (milliCoulombs) is false. The action potential is a change in voltage across a neuron's membrane, not a measure of charge in Coulombs. The resting membrane potential is typically about -70 mV (millivolts), and the membrane potential must usually depolarize to approximately -55 mV from the resting -70 mV to trigger an action potential, which is a change of roughly +15 mV. The peak of the action potential reaches about +30 mV.

Regarding the given questions:

1. The necessary change in the membrane potential for summation of postsynaptic potentials to trigger an action potential is +15 mV (option b).
2. The statement about electric-field lines from a positive point charge spreading out radially and pointing outward is true (option b).
3. During the relative refractory period, the membrane potential can be closer to -45 mV or -80 mV (option c or d), since the neuron is closer to its resting state but not fully repolarized.

The concept of action potential being similar to a battery highlights the ability of the neuron to store and release energy, much like a battery stores charge that can be released under the correct conditions. However, the voltage changes in the action potential are much smaller than the voltages involved in batteries like AA or 9-V batteries.