Crash Course: The Nervous System
I love neurons. I love them so much that my email address is literally neurons@mit.edu. Today I was searching for biomolecular animations of action potentials and I came across an amazing video series from Hank Green at CrashCourse. It beautifully visualizes the nervous system and warrants a highlights reel here. This post was originally written for the EyeWire blog.
Central and Peripheral
Your nervous system is divided up into two areas:
The central nervous system is the brain and spinal column. It’s divided up into many different regions and subregions, each with unique characteristics contributing to activity and cognition. It’s complicated and in the interest of a brief first article here, I’m writing up a separate highlights reel of Crash Course’s CNS video.
The peripheral nervous system, which is also subdivided by function. Your sensory system detects stimuli from parts of the body, for example, texture or temperature when you touch something. The motor system controls movement of muscles, with control originating from the brain and spinal column. It is subdivided into somatic or voluntary muscle movement and autonomic or involuntary movements such as those relating to heart beat, digestion, and pupil dilation. The Autonomic nervous system is further subdivided into Sympathetic, commonly described as “fight or flight” fast response, and Parasympathetic, a complementary system that encourages relaxation.
Together, these systems integrate billions of signals per second to create the sensory and conceptual experience of being you.
Cells of the Nervous System
There are many types of cells in the nervous system. Both Central and Peripheral contain neurons and supporting cells called glia. Cell types are differentiated by structure, function and genomic profile.
At EyeWire, we currently only map neurons. But there are at least as many non-neuron cells, called glia, in the brain. Here’s a brief overview of them, all images thanks to Crash Course:
Neurons
We don’t know exactly how many types of neurons there are in the brain. Neuroscientists estimate that there are hundreds or even thousands of types and subtypes of neurons.
At EyeWire, we’ve been working to create the world’s most complete catalog of retinal neuron types. As we map cells, such as those found in the Countdown to Neuropia, we send 3D models to Seung Lab at Princeton University, where they are analyzed for connectivity. This has been a difficult challenge, which is why we’re building Museum.EyeWire, an upcoming online resource for the world’s research community that aims to create a global consensus of cell types, allowing us to properly model how functional connections allow circuits to perform complex information processing, such as detecting motion.
That’s all for this post. Up next in January: Action Potentials and how neurons communicate.
