Neurons are specialized cells designed to transmit information throughout the nervous system. While they are concentrated in the central nervous system (brain and spinal cord), they also form the peripheral nervous system, making the nervous system as a whole the correct classification for their primary function.

The sodium-potassium pump is an active transport mechanism essential for maintaining the resting membrane potential. It functions by moving three sodium ions out of the cell and two potassium ions into the cell against their respective concentration gradients, utilizing ATP to power this exchange and ensuring the electrochemical balance necessary for neuronal signaling.

Glial cells, or neuroglia, are non-neuronal cells that provide essential support to the nervous system. Their functions include maintaining homeostasis, forming myelin, and providing structural and nutritional support to neurons, including interneurons. Unlike neurons, they do not transmit electrical impulses but are vital for the survival and proper functioning of the neural network.

Sensory neurons, also known as afferent neurons, are specialized nerve cells responsible for converting external stimuli from the environment into internal electrical impulses. These neurons transmit this sensory information from the body's receptors toward the central nervous system, which includes the brain and spinal cord, allowing the organism to perceive and respond to its surroundings effectively.

Effectors are specialized structures, such as muscles or glands, that perform an action in response to a stimulus received from the nervous system. When a motor neuron carries an impulse from the central nervous system, it terminates at an effector, triggering a physiological response like muscle contraction or hormone secretion. Receptors, conversely, detect stimuli, while Schwann cells provide insulation.

The resting membrane potential is the stable, negative electrical charge maintained by a neuron when it is not actively firing an action potential. This state is primarily established by the selective permeability of the membrane to ions and the active transport of sodium and potassium ions, creating a polarized environment essential for future neuronal excitation.

Motor neurons transmit signals from the central nervous system to muscles and glands, enabling movement and various bodily functions. They are responsible for carrying information from the central nervous system to the body's tissues, allowing for the execution of voluntary and involuntary actions.

Effectors are the parts of the body that produce a response to a nervous system signal. The two main categories of effectors are muscles, which respond by contracting to produce movement, and glands, which respond by secreting hormones or other substances. Together, these allow the body to react to internal and external environmental changes effectively.

Neurons are generally classified as having three primary structural components: the cell body (soma), which contains the nucleus; the dendrites, which receive signals from other neurons; and the axon, which transmits electrical impulses away from the cell body to other neurons or muscles. While there are many sub-structures, these three are considered the fundamental parts of a neuron.

Interneurons, also known as association neurons, are the most abundant type of neuron in the human body. They function exclusively within the central nervous system to connect sensory neurons to motor neurons or to other interneurons, forming complex neural circuits that enable higher-order processing, reflex arcs, and communication throughout the brain and spinal cord.