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.

Afferent neurons, also known as sensory neurons, are the neurons that relay information to the central nervous system from the sensory organs. Efferent neurons are the motor neurons that carry the nerve impulses away from the central nervous system to the effectors. Interneurons are the neurons that transmit impulses between other neurons.

Action potentials created by neural impulses are described as being "all or nothing" because the cell either gains sufficient stimulation to release an action potential, or it does not. Once the minimum threshold for excitation is reached, an action potential will be triggered regardless of further stimulation, and no signal will be weaker or stronger than any other. That being said, continued stimulation of a neuron may lead to continued firing of action potentials, which may trigger a stronger or enduring response over time. At the scale of the individual action potential; however, the activity of the neuron may be considered as either a value of 0 (i.e. no action potential), or 1 (i.e. action potential). No decimals are used in this measure.

After crossing the synapse, neurotransmitter molecules bind to receptors on the postsynaptic neuron, initiating an excitatory signal (EPSP). The signal then travels through the dendrites to the cell body, where it becomes an action potential based on the degree of stimulation from other EPSP signals. After traveling through the cell body and down the axon hillock, the signal is sent out by the axon to the axon terminal, or synaptic terminal. There, synaptic vesicles containing neurotransmitters are released into the synaptic cleft (the space between two neurons). Synaptic vesicles fuse with the membrane at the axon and release neurotransmitter into the synaptic cleft. The neurotransmitters diffuse toward the postsynaptic neuron and bind to receptors to begin the process again. Once the signal reaches an effector organ, the neurotransmitters can elicit their ultimate effect.

Myelin is a white, fatty compound that surrounds the axons of white matter neurons. Its purpose is to increase the speed of an action potential.

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 synaptic gap is where two neurons meet. Here neurotransmitters will be released from vesicles in the sending neuron to the receiving neuron. The receiving neuron will receive communication via sensing the neurotransmitters at receptor sites specific for that neurotransmitter. The release of neurotransmitter is stimulated once the action potential has propagated to the axon terminal.

Sodium and potassium are vital components associated with neural electrical transmissions. When it is at rest, a neuron is surrounded by a positive charge due to sodium and maintains an internally negative charge with potassium. When the neuron depolarizes, there is an influx of sodium into the cell. Upon repolarization, there is a potassium efflux where the neuron is restored to its original resting charges.

An action potential is a rapid electrical charge that will propagate down through the neuron. This charge causes a continuous chain reaction through the neuron from the dendrites to the axon terminals by creating a threshold stimulus that allows rapid depolarization and repolarization via the movement of ions across the membrane. This represents the basic construct of how neuronal communication is possible. Although stimulus does seem like a viable answer, a neuron may sense a stimulus but may not propagate a neural impulse. In this case, the stimulus may not be strong enough to activate an action potential. This solicits the "all or nothing" behavior of action potentials. If the stimulus is slightly below the necessary threshold to elicit an action potential, then no impulse can be expected. Conversely, if a stimulus is just at the minimal requirement of the neuron's threshold, then an action potential may be expected; therefore, stimulus would be incorrect. Due to the fact that action potentials function on ionic concentration gradients, ionic equilibrium would also be an incorrect answer. While the terms absolute refractory period and hyperpolarization are related to action potentials, these are merely parts of an action potential that may be argued to be the reasoning to prevent an impulse from traveling backwards. This prevents an action potential from travelling back the way it came. These choices would also be incorrect answers because while they are important, they're only components to an action potential.

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.