Peripheral Nervous System Crash Course AP 12
When it comes to the nervous system, or justyour bodygeneral, let's face it: your brain gets all the props. And it deserves those props! It's a complied,and crucial, and sometimes crazy boss of an organ. But your brain would be pretty useless withouta support team that kept it connected to the outside world. Because frankly, like any leader, the moreisolated your brain gets, the weirder it gets. Put a persona watery, pitchblack sensorydeprivation tank, and you'll see the brain do some really weird stuff. Without a constantflood of external information, the brain starts
to confuse its own thoughts for actual experiences,leading you to hallucinate the taste of cheeseburgers, or the sound of a choir singing, or the sightof pink stampeding elephants. It's your peripheral nervous system thatkeeps things real, by putting your braintouch with the physical environment around you,and allowing it to respond. This network snakes through just about every part of your body,providing the central nervous system with information ranging from the temperature, to the touchof a hand on your shoulder, to a twisted ankle. The peripheral nervous system's sensorynerve receptors spy on the world for the central nervous system, and each type responds todifferent kinds of stimuli.
Thermoreceptors respond to changestemperature.photoreceptors react to light, chemoreceptors pay attention to chemicals, and mechanoreceptorsrespond to pressure, touch, and vibration. And then we've got specialized nerve receptorscalled nociceptors that, unlike those other receptors, fire only to indie pain, whichis the main thing I want to talk about today. Because, as unpleasant as a stickthe eyeor tackthe foot may be, pain is actually a great example of where everything we've talkedabout over the last few weeks all comes together, as we trace a pain signal through your nervoussystem, from the first cuss to the Hello Kitty band aid. By the end of this episode of Crash CourseAnatomy Physiology you'll never think
of a stubbed toe, pounding headache, or burnedtongue the same way again. Most people go to great lengths to avoid pain,but really, it's an incredibly useful sensation, because it helps protect us from ourselves,and from the outside world. If you're feeling physical pain, it probablymeans that your body is under stress, damaged, ordanger, and your nervous system is sendinga cease and desist signal to stop twisting your arm like that, or to back away from that bonfire,or please seek medical attention, like, RIGHT NOW. Sothat way, pain is actually good foryou that's why it exists. I'm not saying it's pleasant, but if you've ever wishedfor an XMenlike power to be impervious to
pain, I've gotta say, that is one foolishmonkey's paw of a wish. Just ask Ashlyn Blocker. She's got a geneticmutation that's given her a total insensitivity to any kind of pain. And as a result, she'sabsentmindedly dunked her handspots of boiling water, run around for days without noticingbroken bones, and nearly chewed off her own tongue. Luckily, such congenital conditions are veryrare. The rest of us have a whole nervous system dedied to making sure our bodies react witha predictable chain of events at the first sign of damage. Like say you just wake up and you're extraordinarilyhungry for some reason, so you run downstairs to grab some clam chowder, but you didn't putany shoes on and suddenly you're like, â€œYOWW!â€�
There's a tack, fell out of the wall, andyou stepped right on it of course. Your foot immediately lifts off the ground,and then you're assuring your that you're not yelling at her, you're just yelling,and then you limp over to the couch, and sit down, and you pull up your foot, and removethat spiny devil from your flesh. You want to talk physiology? So what exactlyjust happenedyour body? Well, the first step was a changeyourenvironment that is, a stimulus that activated some of your sensory receptors. In this case, it was a change from the probablycompletely ignored feeling of bare skin on