|Original (French) Title||L'Œil|
|The Neurones||The Ear|
The episode begins on a sunny day when Peter opens a window and spots a butterfly. Then, the narrator explains the purpose of human eyes:
"The eye is an extension of the brain, and it is the brain's main instrument for observing the outside world.</br>The image received by the eyes is broken down for transmission along the optic nerves, then reassembled by the brain."The scene zooms into the air, showing a lot of Photons. One of them stops and introduces himself to the viewer and explains his properties of how fast he is, how do they react with Electrons and so. Peter calls his Mum to see the butterfly. At this moment, two Photons discuss about how tiny they are that they're invisible by naked eye. One of them tries to show it by flying around and grimacing in front of them, proving that, despite being invisible to humans, they make things visible for them.
Peter's Mum leaves and the scene switches to Peter's eyes registering the image. The visual center receives a message that picture is blurry and that the focus needs to increase, and so requests the refocusing of lens in charge of ciliary muscles. The Neurotransmitter reaches the storage of chemical messengers and reports the situation. The Chief's assistant releases the messengers who proceed the messages to the ciliary muscles. They tighten, extending the lens. The visual center receives only one half of butterfly Peter's focused on, but realizes that there was a slight mistake when another Neurotransmitter reaches the nucleus. As the message is now correctly understood, the full picture of the butterfly is made.
The butterfly flies away to a flower it rests on. A sunbeam falls on its wings, showing a lot of photons matching its colors and reflecting. The scene switches to Red Corpuscles traveling through optic artery in the left eye. Lieutenant Jumbo greets Globus and notices a marching group of Carotenes. Globin is curious and Globus explains to her that they're products of Vitamin A. At one point, she notices how light reflects off Hemo's oxygen bubbles, creating a colorful spectrum. Globus tells that, after a long journey from the Sun, the sunbeams reach retina that lines the interior of the eye and introduces the presence of photo-receptors, rods and cones. He then explains how the information is passed from retina to the cells down the optic nerve. Eventually, information reaches the brain and, finally, a picture is formed.
Peter's Mum comes back and Peter asks her how can his eyes see in color. She replies that it's not really what eyes do, but rather brain. He is confused, but she doesn't explain what she meant. The assistants of sleeping Maestro see a confused Peter and the former wakes up and takes the latter into the nucleus to explain to him how can one see with their brain. He shows him multiple screens of various mind-breaking pictures and then takes an orange from the screen. Maestro explains that the eyes receive the signals, but the brain has to decide how to decode them, and that both eyes don't always see the same picture. Peter then leaves the nucleus back into the outside world. He tells Mum he ate an orange he got "from an old man who lives inside his brain", much to her shock.
Later, Peter's Mum shows her son a surprise: a puppy. He thanks her on it and he promises that he'll make sure he's safe and well-taught. He decides to name him Roly Poly. The next day, he ties the dog to the root of a tree to ensure it doesn't run away as he leaves for school. However, he rips the rope and wanders away. After Peter is back from school, he notices the cut rope in shock. He and his Mum begin to look for the dog. The former is really sad as Mum tries to assure him that they'll find him. Later, Peter sits by the tree, holding the cut rope, crying. However, Roly Poly comes back out from a bush and reports the good news. He plays with Roly Poly later on, but the weather becomes very windy and the narrator decides to introduce the viewer to the purpose of tears.
Inside of a lacrimal gland, a lot of Enzymes pour Salt in a pool of water to form tears. The Chief tests how salty are tears and requests more Salt. After testing once more, he orders for tears to be ejected down the tube, cleaning the dirt particles.
As weather is becoming more and more windy, many dust, dirt and gems are caught in eyes, causing irritation. The lacrimal Chief receives the order to eject tears to wash the debris away. The Neurotransmitter that delivered the message, however, takes a break by swimming in the pool, almost filthying the tears in the process. The Chief then sees the lysosomes, ready to take out the germs and dirt in the eye. The Enzymes collect them in buckets of tears and pour them down lacrimal canals. Once at cornea, a group of these Enzymes goes further down the eyelids to intercept the Viruses. The latter tries to avoid the former, but are defeated and washed away in tears, pouring down in nasal cavity. Mum approaches him and warns him not to rub his eyes with dirty hands to avoid getting conjunctivitis.
- The first episode to deal with senses.
- The return of younger versions in this episode.
- The cleaning Enzymes incorrectly introduced themselves as lysosomes, which are cell organelles responsible for disposal of waste products. The lysosomes themselves are full of enzymes, however.
- The first appearance of Roly Poly.
- Eyes are sensory organs that provide the organism with vision by converting light into nerve impulses.
- Human eyes, compared to other types of animals, have advanced vision with a better color palette, able to register three colors and mix them: red, green and blue.
- A human eye consists of following parts:
- Helping parts:
- Eyelashes — sharp strands of hair that catch any dust or larger particles and prevent them from entering the eye.
- Eyelids — double skin flaps (the upper part is more advanced that the lower one) that work with eyelashes to prevent the intruding particles from entering the eye. They splash the tears across the eye as well.
- Eyebrows — concentrations of hair in horizontal lines above each eye to prevent the eye being invaded from factors that concern the upper portions of the body, like sweat.
- Lacrimal glands — exocrine glands that release tears on eyes. Tears are clear fluids of salty taste with a purpose to clean the eye, protecting it from microbes and preventing it from drying.
- Conjunctiva — a mucous membrane on the other side of eyelids, helping lubricate the eye with mucus and tears. Particularly, it's exposed to many unwanted factors, resulting in low defense and a common inflammation called conjunctivitis.
- Eyeballs (the layers are written in bold italics):
- Sclera — opaque, white, protective layer covering the eyeball, contrasting with the iris.
- Cornea — transparent, front part that covers the iris and the pupil. It refracts light that passes on to lens.
- Iris — a thin, colored muscular ring that controls the diameter of pupil, and thus the amount of light that enters the eye.
- Pupil — a hole located in the middle of the iris that lets the light enter the interior. It appears black due to all the light being absorbed by the tissue and none of it reflecting.
- Lens — a transparent, biconvex structure that refracts the light focused on the retina. It's controlled by the ciliary body, shortening or extending to create a picture sharp enough to be registered.
- Vitreous body — a gelatinous liquid that gives volume to the eye.
- Choroid — the vascular layer that contains connective tissues. Located between the sclera and the retina, providing oxygen and nutrients to the cells in retina.
- Retina — the innermost, light-sensitive layer. Contains the large number of photo-receptors; the cells that respond to light signals. The cones are responsible for the human eye being able to recognize color, while the rods help us adapt in dark. Retina has two major spots:
- Macula — the area where concentration of the photo-receptors is the largest.
- Optic disc — located at the beginning of optic nerve. It contains no photo-receptors.
- Helping parts: