|Original (French) Title||Les Neurones|
|The Brain||The Eye|
The episode begins as narrator gives a short introduction of neurons:
"Neurons, or nerve cells, are the material that our brains and nervous system are made of. We're born with all these cells, and their development stops by the time we're one year old. They're the only cells in the human body that are never removed. However, their ramifications or branches keep on growing. Do you know that hundred thousand neurons could fit into a pinhead? And the number of their possible combinations could contain several thousand digits. Hard to imagine, isn't it?
What is the function of these billions of neurons? It's to perceive the outside world and get us to grasp it, to regulate, harmonize and coordinate the perfect functioning of our inside world — a world of the human body. It's all very complicated, my friends, so let's take a closer look."
The current part of the story takes place in Claire's body while many information are detected in nucleus of the focused neuron. The chiefs find multiple problems during running, like a lot of dust in the air, dry throat and tight shoes. Maestro decides that it's the best if a cough should be initiated and if heart should beat faster. As two Neurotransmitters exit the nucleus, they discuss their routes and the one that carries message for faster pulse rate calls his colleague lucky considering that cough is a reflex. In the meantime, an Enzyme tries to make its way to a Ribosome but is interrupted by the quick traffic. After the Neurotransmitter carrying order to cough reaches other nerve cell (without passing the message to other messengers along the axon), the system releases chemical messengers to create a synaptic connection.
The preparation for synapse is a hassle and many chemical messengers argue and push each other around, forgetting that each one of them fits into only one lock. Soon, all of them match their locks and the synapse is initiated. The Neurotransmitters sprint quickly out of nucleus and receive their messages from chemical messengers. The impulses reach the system which releases the chemical messengers with following order:
"Attention, please! We only accept Acetylcholines — nobody else! Order to intercept all intruders."The assistants make sure only the Acetylcholine messengers reach the synapse. After the connection is realized, the system finally carries out the reflex action:
"Order to cough about to be transmitted to intercostal muscles.The reflex action is performed; Claire clears her throat by coughing.
ORDER RECEIVED AND TRANSMITTED!"
The scene switches to Red Corpuscles on their daily routines of carrying oxygen. Hemo feels heavier than usual, but that is because the heartbeat rate is yet to be accelerated. The impulses have already been sent, but due to heart having its own conduction system, the messenger has to go the other way around through sympathicus. However, he runs through and delivers the message. The main chief orders to increase the rate from 95 to 110 beats per minute, resulting in the electric conduction system and corpuscles working faster.
Stroppy and Nabot, smoking on a bench, notice Claire, Peter, Peter's Sister and Jumbo running. They decide to prank them by wrapping one of the fence wires across the path so one of them would eventually trip over. Peter takes the lead, not noticing the wire, therefore falling over it and hurting himself. As soon as this happens, the interior of a neuron shakes violently and Maestro orders to send the pain messengers.
On their way to the brain, the pain messengers disrupt the traffic and almost hurt several Enzymes and chemical messengers along the way. One of the regular Neurotransmitters, however, manages to reach the nucleus and inform the Chief. He declares that there is too many pain impulses and orders the release of enkephalins. In appearance of tapwater, the enkephalins release a pink, sticky substance that stops several pain messengers from coming through. In the outside world, Claire helps Peter while Jumbo scares the bullies away. The four teens reach a bench on which Claire sits with Peter. The latter admits that relaxing from time to time feels useful.
The episode ends with following scene: Globus exclaims how there is always some task for nervous system and that it's always active and that the actions it can take show the superiority of humans. Globus shows a nearby Neurotransmitter doing arithmetic, but is interrupted when a Virus messes with the equation. He manages to change the situation to better and also to chase the Virus away. Then, Maestro comes and presents much more complex examples of human ideas through mind, after which the narrator ends the episode informing that all aspects of human brain's properties can be the result of chemistry.
- This episode had a great focus on biochemistry.
- This episode introduces the chemical messengers that realize a synaptic connection.
- This is the first episode to show the appearance of heart's electric conduction system.
- The third episode in row to feature the four main human children as teenagers in the same setting.
- Neurons (commonly known as nerve cells) have the role of conductors throughout nervous system.
- The direction of impulse is receptors (registering the impulse) > central nervous system > effectors (carrying out the requested task).
- Neurons greatly differ from other somatic cells in body due to the fact that, regardless of lifetime or an injury, they never perform mitosis, and thus can never be replaced. However, their ramifications keep extending through daily experiences with information coming from the outside world, which increases intellectual ability.
- They are surrounded by glial cells, cells that nourish, protect, support and isolate neurons. Despite they are centered around neurons, they are able to divide.
- A nerve cell consists of following parts:
- Dendrite — short, branched extensions. They are the start points of neurotransmitters and are part of the impulse that reaches soma as the next destination.
- Soma — bulbous portion of the nerve cell. Contains the nucleus and passes the impulse from dendrites to down the axon.
- Axon — a singular extension that branches in the end to other nerve cells.
- Myelin sheath — a membrane made of myelin, a lipid-rich substance with a task to speeds up the impulse.
- Axon terminal — the very end of the axon, splitting in several thousand endings that, through synapse, pass the impulse onto another nerve cell.