Question

The resting membrane potential for neuron A is -70m V, while the resting potential for neuron B is -50m V. The threshold voltage for the production of an action potential is -35mV for both neurons. Which of the following statements is incorrect?
A. Neuron A must depolarise by 35mV to reach the threshold voltage.
B. Neuron B must hyperpolarise by 15mV to reach the threshold voltage.
C. The inside of both neurons is negatively charged with respect to the outside.
D. A single EPSP received by neuron A would cause it to depolarise slightly.

Answer 1

Hint:
A resting (non-signaling) neuron has a voltage across its membrane referred to as the resting membrane potential or the resting potential. The resting potential is defined by concentration gradients of ions through the membrane and by membrane permeability to every kind of ion.

Complete answer:
Threshold potential is the least potential difference that must be reached with the goal to fire an action potential. For most neurons in the human body, this lies at -55 mV, so a signal to a resting cell must increase the membrane potential from -70 mV. The signal has to overcome an even greater potential difference in order to achieve the threshold if the cell is hyperpolarised. Changes in the potential that do not reach -55 mV cause any change in the cell. Changes that go beyond -55 mV do not vary in effect from those that just reach -55 mV since firing an action potential is an all-or-nothing event. The resting membrane potential is defined by the unequal distribution of ions (charged atoms) between the outside and the inside of the cell, and by the various permeability of the membrane to various types of ions. If the membrane potential becomes more positive than it is at the resting potential, the membrane is said to be depolarized. If the membrane potential becomes much more negative than it is at the resting potential, the membrane is said to be hyperpolarised. Hyperpolarising neuron B by 15 mV would make its membrane potential -65mV, taking it farther away from the threshold voltage required to fire an action potential.

Option ‘B’ is correct

Note:
Hyperpolarisation is the name given to the period of overshoot of the internal cell potential to values more negative than the normal rest state. Depolarisation in a nerve cell takes place once the cell undergoes an electrical shift. Most cells are negatively charged compared to their environment.