Say I was supposed to write a paper about visual processing. I decided to use the Kandel, Schwartz, and Jessel text as my reference. Light entering the cornea is projected onto the back of the eye, where it is converted into an electrical signal by a specialized sensory organ, the retina. These signals are then sent through the optic nerve to higher centers in the brain for further processing necessary for perception.
First light enters the cornea and is projected onto the retina in the back of the eye.
Then it is converted into an electrical signal and sent through the optic nerve to higher centers in the brain. There further processing that is necessary for perception is performed. The retina on the back of the eye is where the electrical signal is generated. These are words that the author of the book came up with. They relate to the organization of the paragraph.