Definition of an Axon
The axon is a long, slender projection of a nerve cell (neuron) that typically conducts electrical impulses known as action potentials away from the neuron's cell body (soma). Its primary function is to transmit information to other neurons, muscles, or glands, serving as the neuron's output pathway.
Structure and Myelin Sheath
Axons can vary significantly in length, from a few micrometers to over a meter, enabling long-distance communication in the body. Many axons, especially in vertebrates, are insulated by a fatty layer called the myelin sheath. This sheath dramatically increases the speed of electrical signal conduction, with unmyelinated gaps known as Nodes of Ranvier facilitating faster impulse propagation.
Role in Neural Communication
When a neuron receives sufficient stimulation, it generates an action potential that travels rapidly down the axon. Upon reaching the axon terminals, this electrical signal triggers the release of neurotransmitters into the synapse, a junction where information is relayed to an adjacent cell. This precise and rapid communication is fundamental to all nervous system activities, including thought, movement, and sensory perception.
Clinical Significance
The integrity of axons is crucial for proper nervous system function. Damage to axons, such as in traumatic brain injury or spinal cord injury, can severely impair signal transmission and lead to neurological deficits. Diseases like multiple sclerosis involve the degradation of the myelin sheath, disrupting axonal conduction and resulting in a wide array of symptoms affecting motor control, sensation, and cognitive functions.