Afferent vs Efferent
The nervous system is the director of all body activities. Its major functions include communication and control. The nervous system is made up of two major cells; neuron and neuroglia. The neuron is the structural and functional unit of the nervous system. These cells are specialized to respond to chemical and physical stimuli and to conduct and transfer messages throughout the body. Generally, the human brain can regulate more than 10 billion neurons at all times. Each neuron has three parts; namely, a cell body, an axon, and numerous dendrites. Axon and dendrites are collectively called processes of a neuron. Depending on the shapes and functions of the neurons, there are three types of neurons; namely, afferent neurons, interneurons, and efferent neurons. These three types have different characteristic features and functions.
The meaning of afferent is carrying sensory information such as nerve impulse toward a central organ or a part like brain from the periphery of the body. Afferent or sensory neurons are specialized cells that help to conduct nerve impulse to the central nervous system from all parts of the body. Afferent neurons are activated by physical modalities such as light, sound, temperature etc. These cells have sensory receptors located on their cell membrane and are capable of converting stimuli into electronic nerve impulses. These neurons are pseudounipolar neurons that have a single long dendrite and a short axon. The cell bodies are smooth, round shaped and are located in the peripheral nervous system. Their axons travel from ganglion, to ganglion and lead back to the spinal cord. Single long myelinated dendrite is similar to an axon and is responsible for transmitting sensory information or nerve impulse from sensory receptors to its cell body.
Efferent neurons (also known as motor neurons) are found inside the central nervous systems (in the gray matter of spinal cord and medulla oblongata) that are responsible for receiving information from other neurons and transmitting nerve impulse to the periphery of the body such as muscles, glands etc. The cell body is satellite shaped and is connected to a long axon and several shorter dendrites. The axon forms a neuromuscular junction with the effectors. The impulse enters through dendrites and leaves it through the single axon to the other end.
What is the difference between Afferent and Efferent Neuron?
• Afferent neurons are responsible for receiving and transmitting messages to the central nervous system from all parts of the body. In contrast, efferent neurons are responsible for receiving and transmitting the messages from the central nervous system to all parts of the body.
• Afferent neurons make up sensory nerves while efferent neurons make up motor nerves.
• Afferent neurons have a single long dendrite and a short axon whereas efferent neurons have a single long axon and several dendrites.
• The cell body of afferent neuron is perfectly rounded and smooth whereas that of efferent neuron is satellite shaped.
• Generally, afferent neurons are located just outside the central nervous system whereas efferent neurons are located inside the central nervous system.
• Efferent neurons get their input from the other neurons including interneurons and afferent neurons. Unlike efferent neurons, afferent neurons are activated by external stimuli such as vision, hearing, touch etc.
• Unlike afferent neurons, efferent neurons involve in muscular control in the body.