Final answer:
The speed of a neural impulse is increased by the myelin sheath. This sheath, which is produced by glial cells, acts as an insulator preventing signal dissipation while improving transmission rate. Gaps in the sheath, known as Nodes of Ranvier, help 'recharge' the signal during transmission.
Step-by-step explanation:
The speed at which a neural impulse travels is increased when the axon is encased by a myelin sheath. Myelin sheaths, produced by glial cells, act as insulators for the axons in the nervous system, preventing the dissipation of electrical signals and therefore accelerating their transmission. Myelin sheaths encompass the axon in a way similar to the pastry on a 'pig in a blanket', completely enclosing the axon after several layers. The structure helps in maintaining the integrity of the nerve impulse as it travels along the axons, which can be as long as a meter in human motor neurons. Nodes of Ranvier are small gaps in the myelin sheath where the signal gets 'recharged' during transmission.
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