The membrane potential of a neuron rests at -70mV when not receiving stimulation. After receiving sufficient stimulation to pass the threshold potential of -55mV, the action potential triggers, rapidly increasing the membrane potential to a peak of 40mV, before dropping to -90mV during the refractory period, and finally returning to a resting potential of -70mV after the action potential has completed. This entire process can take place in as little as 4 milliseconds. 

All animal cells are polarized, because they maintain a difference in voltage between their interiors and their surroundings. This is measured at the cell membranes and known as a membrane potential. The resting potential of a neuron is the value its membrane potential keeps as long as it is not receiving stimulation or undergoing an action potential. In a typical neuron, this resting potential is -70 millivolts (mV). This value does not reflect the average time a neuron spends at rest. The stage of hyperpolarization of a neuron is known as the refractory period. Although the resting potential of a neuron implicates its chemical state and contributes to its probability of firing an action potential, neither of these statements are correct definitions for the term.

A stimulus begins the propagation of the action potential, and channels open to admit sodium into the cell. This leads to a rapid depolarization, as the positively charged sodium ions rush in to balance out the negative resting potential of the neuron (-70mV). At the peak of depolarization, the interior of the cell becomes more positively charged than the exterior. Repolarization subsequently occurs, as the sodium channels are closed, and potassium channels opened in their stead, allowing positively charged potassium ions to exit the cell, restoring the negative membrane potential of the neuron. The refractory period ensues. After the opening and closing of the sodium channels, they are briefly set in an inactive state, and cannot be opened again until the membrane resting potential is restored. During this time, sodium and potassium pumps return sodium to the exterior and potassium to the interior of the cell. As it is impossible for any region of the cell to depolarize during this stage, action potentials may not occur and the neuron is at rest.

A stimulus begins the propagation of the action potential, and channels open to admit sodium into the cell. This leads to a rapid depolarization, as the positively charged sodium ions rush in to balance out the negative resting potential of the neuron (-70mV). At the peak of depolarization, the interior of the cell becomes more positively charged than the exterior. Repolarization subsequently occurs, as the sodium channels are closed, and potassium channels opened in their stead, allowing positively charged potassium ions to exit the cell, restoring the negative membrane potential of the neuron. The refractory period ensues. After the opening and closing of the sodium channels, they are briefly set in an inactive state, and cannot be opened again until the membrane resting potential is restored. During this time, sodium and potassium pumps return sodium to the exterior and potassium to the interior of the cell. As it is impossible for any region of the cell to depolarize during this stage, action potentials may not occur and the neuron is at rest.

Myelin is a fatty substance produced by glial cells which encases some neurons and serves to insulate them, allowing electrical signals to transmit more quickly along them. Myelin cannot protect the neurons from radiation damage, or from attack by pathogens. Glial cells in the brain form myelin, and contribute to the nourishment and support of nerve cells; however, myelin itself does not serve this function. When myelin deteriorates, nerve transmission can be impaired, as in the case of multiple sclerosis.

Neurons communicate both through transmission of electrical signals (i.e. action potential), and chemical signals (i.e. neurotransmitters). Although the action potential is triggered by electrical stimulation and propagates along the cell axon as an electrical depolarization, the information carried by this charge is not passed on to the next neuron via the electrical charge itself. Instead, the action potential signals for the release of neurotransmitters from the terminal buttons at the end of the axon, which bind to receptors on the dendrites of linked neurons in a form of chemical communication. It is important to note that auditory signals are not utilized by neurons to communicate.

The correct answer is "neurons have specialized parts called axons and dendrites, which help to send and receive information from other neurons." Specifically, axons take information away from the cell body and dendrites bring information to the cell body. Only neurons have these two specialized parts, which helps them to maintain electrochemical communication with other neurons.

Glia, also known as glial cells, are non-neuronal cells that provide support and protection for neurons located in the central nervous system. Neurons are made up of dendrites, axons, and a cell body (which is covered by the myelin sheath).

The refractory period can be thought of as the recovery time that a neuron needs between action potentials. During this period, no additional neurotransmitters can be fired. Most refractory periods are quite short, lasting less than a single second.

The myelin sheath is a layer of fatty tissue that encases the fibers of most neurons. The myelin sheath enables vastly greater transmission speed of neural impulses as the impulse hops from one node to the next.