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.

The sodium potassium pump moves sodium and potassium against their concentration gradient. The pump moves 3 sodium ions out of the cell and 2 potassium ions into the cell. This pump requires ATP (cellular energy) since it is pumping ions against their gradient.

The limbic system is primarily located in the forebrain. Key structures of the limbic system include the hypothalamus (which moderates biological needs, such as hunger), hippocampus (which stores long-term memory), and the amygdala (which plays a role in emotional associations). The primary purposes of the limbic system are to store memories, moderate survival behaviors, and generate emotional responses. It plays a key role in biological motivations by determining such responses as hunger, sex drive, and fear.

The medulla oblongata is located in the hindbrain and brain stem. Its key purpose is to facilitate functions of the autonomic nervous system, initiating such things as respiration, heart beat, and blood pressure. It is not considered part of the limbic system.

Alcohol is a depressant that suppresses the secretion of excitatory neurotransmitters like glutamate, while increasing the production of the inhibitory neurotransmitter GABA. At the same time, it increases the release of dopamine to the nucleus accumbens, creating a pleasure sensation.