The Nervous System, Part 1: Crash Course Anatomy & Physiology #8

This morning was a typical morning for me. I woke up thinking about that dream that I

keep having about the guy in the sloth suit, and then I got dressed because I was cold,

and then I made some toast with butter ‘cause I was hungry, and then I let the dog out ‘cause

she was whining and staring and me, and then I made some tea but I let it cool off before

I drank it because I burned my mouth yesterday.

In addition to being just part of my morning ritual, all of these actions are examples

of what my nervous system does for me.

The weirdo dream, the sensation of cold air and hot tea, deciding what to put on the toast,

going to the door at the sound of the dog -- all that was processed and executed by

electrical and chemical signals to and from nerve cells.

You can’t oversell the importance of the nervous system.

It controls ALL THE THINGS!

All your organs, all your physiological and psychological reactions, even your body’s

other major controlling force, the endocrine system, bows down before the nervous system.

There is no “you” without it. There is no “me” without it. There’s no dogs

without it. There’s no animals. There’s no -- there’s no things -- there’s things.

It’s important. That’s why we’re dedicating the next several episodes to the fundamentals

of the nervous system -- its anatomy and organization, how it communicates, and what happens when

it gets damaged.

This is mission control, people!

Even though pretty much all animals -- except super simple ones like sponges -- have a nervous

system, ours is probably the most distinctive feature of our species.

From writing novels, to debating time travel, to juggling knives -- all of your thoughts,

and actions, and emotions can be boiled down into three principal functions -- sensory

input, integration, and motor output.

Imagine a spider walking onto your bare knee.

The sensory receptors on your skin detect those eight little legs -- that information

is your sensory input.

From there your nervous system processes that input, and decides what should be done about

it. That’s called integration -- like, should I be all zen about it and just let it walk

over me, or should I not be zen and freak out and run around screaming, “SPIDER!”?

Your hand lashing out to remove the spider, and maybe your accompanying banshee scream,

is the motor output -- the response that occurs when your nervous system activates certain