Mr. harrison is an 82 year-old man bedridden gentleman who has discovered a new interest in learning about his body. while being tended by the visiting nurse, he remarks that the supporting cells in nervous tissue (such as schwann cells and oligodendrocytes) act like the rubber coating around household wiring. what does he mean by his analogy?

He meant that the supporting cells form a insulating coat on the nerve fibre called myelin seath. The myelin Sheath act similar to the rubber coating of household wiring because it electrically insulates the nerve fibre and speeds of conduction of nerve impulse..

Explanation:

The supporting cells of the nervous system are together called neuroglia or glial cells.Unlike neurons these cells can divide in the mature nervous system and do not conduct nerve impulse.Out of six types of glial cells, four are located in the central nervous system (CNS) and they are;astrocytes, oligodendrocytes, ependymal cells and microglia.The remaining two types are the part of Peripheral nervous system (PNS) and include Schwann cells and Sattelite cells.Among these , the oligodendrocytes of the CNS and Schwann cells of the PNS  forms myelin sheath on the axons of the nerve cell that act similar to the rubber coating on the household wiring.The myelin sheath electrically insulates the axon of a neuron and increase the speed of conduction of nerve impulse.

Where's the picture of the model?

It forms into a full nebula/star