A neuron has three basic parts: the dendrites, the cell body, and the axons. Some neurons have a fatty layer covering called around their axons. This layer isn't continuous, and the gaps are called . The action potential jumps through these gaps to the transmission.

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.

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!