A neurite is a projection extending from the cell body of a neuron. Like branches on a tree, neurites grow outward to form the vast, interconnected networks of the nervous system. Through these extensions, neurons send and receive the signals that underpin all brain functions. The term “neurite” is often used when discussing developing neurons, as it can be difficult to distinguish between the different types of projections.
The Two Main Types of Neurites
Neurons produce two distinct kinds of neurites with specialized roles: axons and dendrites. Dendrites are the primary receivers of information. Their highly branched structure allows them to collect signals from many other neurons at once. These incoming signals are then integrated and passed toward the neuron’s cell body.
In contrast, the axon is the primary transmitter, carrying signals away from the cell body. A neuron has a single axon, which can be very long—sometimes extending over a meter in humans—to connect distant parts of the nervous system. This slender projection acts as a high-speed cable, delivering messages to targets like other neurons, muscle cells, or glands.
How Neurites Grow and Form Connections
The process of a neurite extending to find its target is known as neurite outgrowth. This journey is led by a structure at the tip of the growing neurite called the growth cone. The growth cone acts as a microscopic explorer, sampling its environment for chemical guidance cues that tell it where to go. This navigation is driven by a dynamic internal scaffolding of actin filaments and microtubules.
These guidance cues are molecules that either attract or repel the growth cone. Attractant molecules draw the growing neurite toward its destination, while repellent molecules create “keep out” zones that prevent it from growing into incorrect territories. The growth cone integrates these competing signals to steer along a precise pathway.
When the growth cone reaches its destination, it transforms to form a synapse. A synapse is a specialized junction where the axon terminal of one neuron contacts a dendrite of another. At this connection point, chemical neurotransmitters are passed from the sending neuron to the receiving one, completing a functional circuit.
Neurites and Brain Plasticity
Neurites are not static; they are part of the brain’s ability to adapt throughout life, a concept known as brain plasticity. This process allows the brain to reorganize itself in response to new experiences, learning, and memory. The strengthening of synapses, growth of new dendritic branches, and formation of protrusions called dendritic spines are all physical manifestations of plasticity.
When you learn a new skill, like playing an instrument, repeated practice strengthens specific neural pathways. New synapses may form, existing ones can become more efficient, and new dendritic spines emerge to create more points of contact. This physical reshaping of the brain’s wiring solidifies the new knowledge.
This adaptability also allows the brain to compensate for minor injuries. If one sensory input is lost, the brain regions that formerly processed it can be repurposed as neurites from other pathways form new connections in that area. This ongoing modification of neural circuits helps the brain meet new demands.
Impact on Neurological Conditions
Disruptions to neurite structure and function are implicated in many neurological disorders. In Alzheimer’s disease, for example, the formation of neuritic plaques is a primary indicator. These are dense clusters of protein fragments that accumulate between neurons, disrupting nearby neurites and interfering with cell-to-cell communication.
Physical nerve injury also impacts neurites, particularly axons. When an axon is severed in the peripheral nervous system (nerves in the limbs and organs), it has a limited capacity to regrow. However, axons within the central nervous system—the brain and spinal cord—do not regenerate effectively after injury, which is why spinal cord injuries often result in permanent functional loss.