The brain is made up of many neurons that communicate with each other. Communication between afferent and efferent neurons occurs in the form of electrochemical signals. The nervous system receives signals from afferent nerve fibers and then sends signals via efferent nerve fibers to either other areas of the nervous system or to organs in the body, such as a gland or muscle. Signaling between afferent and efferent neurons occurs through interneurons.
One of the most common types of neuron in the central nervous system is the multipolar neuron. This type of neuron consists of the soma, or cell body, an axon, and three or more dendrites. The soma is the largest part of the neuron and is where many different processes occur. Attached to the cell body are dendrites, which receive signals from other neurons, and a long axon that separates into a few branches. Located on these branches are terminal buttons which send signals and form synapses with other neurons.
Surrounding the axon of a neuron is a cell membrane that is electrically charged. When the electrical charge of the axon is reversed relative to the outside of the cell membrane, a signal is carried from the cell body, down the axon, to the terminal buttons. This change in electrical charge is called an action potential. Communication between afferent and efferent neurons or nerves fibers is able to occur because of this process.
The neurotransmitter then binds to receptors that are located on the cell membrane of the neighboring neuron called the postsynaptic neuron, which forms a synapse. A synapse is a conjunction between a terminal button on one neuron to the cell membrane of a neighboring neuron. This allows for neurons to communicate with each other. Communication between afferent and efferent neurons occurs in this way via interneurons located entirely in the central nervous system.
Different areas in the nervous system receive signals from afferent neurons. Afferent neurons that are able to respond to physiological changes or that are connected directly with sensory receptors are called sensory neurons. This type of neuron recognizes internal and external environmental changes and sends information about these changes to the central nervous system. Efferent neurons send signals from the central nervous system to either other areas in the nervous system or to muscles or glands. These neurons are called motor neurons and, when an action potential moves down its axon, it results in a muscle twitch.