Final answer:
Demyelination leads to reduced conduction velocity of nerve impulses due to a decrease in the length constant and an increase in the time constant. This affects nerve impulse propagation, resulting in slower action potential transmission along the axon.
Step-by-step explanation:
Demyelination results in a decrease in the length constant and an increase in the time constant, which together lead to a reduction in conduction velocity of nerve impulses. In a healthy myelinated axon, the action potential jumps from one node of Ranvier to the next in a process known as saltatory conduction, which is much faster than the continuous conduction seen in unmyelinated axons.
Myelination and the diameter of an axon are both factors that influence the speed of nerve impulse propagation. The action potential can propagate more quickly in wider axons, similar to how water flows faster in a wider river compared to a narrow creek. This is partly due to the concept of resistance, which affects conduction in electrical wires, plumbing, and biological axons differently.
In the context of demyelination, the decreased length constant means that the electrical charge does not spread as far along the axon before it significantly diminishes. The increased time constant means that it takes longer for the membrane potential to change in response to a stimulus. Therefore, demyelination generally slows down the action potential conduction velocity, which can result in neurological symptoms.