Answer:
1. Myelin sheath
2. Nodes of Ranvier
3. Speed up
Explanation:
A neuron is the fundamental unit of the nervous system and structured into the dendrites, the axons and the cell body.
1. The axons of the neuron are covered by a layer composed of the fatty acids and the proteins that is the constituents of the plasma membrane. This layer is known as the myelin sheath. The myelin sheath provides insulation and increases the speed of transmission.
2. Nodes of Ranvier: The myelin sheath around axons does not form continuous but have discontinuous structures due to the gaps in the sheath. These gaps are known as the Nodes of Ranvier.
3. The nodes of Ranvier increase the speed of the electrical impulse transmission through the neuron.