Only so long ago, (ie January) I started my Neuro100 class with the wonderful Professor Wasserman as our guide. If there’s anything I’ve learn in these three months, it’s that everything we want to know and ever have known was because someone asked a question. In a lot of my future science blogs, many of my notes will act as answers to questions that the textbook rhetorically asked and answers to questions I asked in office hours.
Now on to the notes!
Our first class dealt with the basics: what is the neuron, and why is it the unit of the nervous system? The brain is a grey, gelatinous mass when taken out of a human (or model organism) head. How do we find all the magically bits that describe the structures of the cells that make up the brain?
Histology in the Brain
Stains! And lots of them.
Histology: the mircoscopic study of the stucture of tissuses.
In my class, we focused on three types:
|Fast luxol blue||stains blue with red blood cells turquoise, and the cell bodies are red|
|Golgi stain||silver chromate reacts with a few of the neurons to show the whole neuron|
|Nissl stain||stains cell bodies of neurons|
The Typical Neuron
The function of neurons cannot be understood without understanding the structure and function of the membrane and its associated proteins.
Now that we can see the neurons, we can start understanding what’s going on in them. Neurons typically have a soma (cell body) 20µm diameter and filled with cystol. The neuron has a nucleus, mitochondria, rER and sER. You know, the typical cell in general.
What makes the neuron unique is its projections and excitable membrane; the axon, dendrites, and synapses. In the axon leading up to the synapse, there are loads of synaptic vesicles, mitochondria, and proteins. Surprisingly, there are not microtubules or ribosomes here. How do the proteins get to the ends of the terminals??
Transport to the hungry hungry Axons
Wallerian degeneration (the death of the axon) occurs when axoplasmic transport is halted.
How? A string is a good God.
|Axoplasmic transport||Fast axoplasmic transport|
|1-10mm per day||1000mm per day|
|very slow||very fast|
To diversify of science lingo we add two definitions that show transport in two directions.
Anterograde Transport (soma->axon->terminal) the protein “kinesin” is the walkway of most material, and it is fueled by ATP. Axoplasmic transport from a neuron’s soma to the axon terminal
Retrograde transport (terminal->axon->soma) a separate pathway from the terminal to the soma. Some viruses hitch a ride on this sort of transport. eg rabies (fatal), Herpes simplex (cold sores) Hate these!
Classifying Neurons and Glia
The Neuron Doctrine: Brain cells communicate by contact, not continuity.
So many neurons, so little time…
|Uni -1||bi 2||multi- poly- many|
Rapid fire Questions
What is a synapse? The gap between two neurons.
What is a neurotransmitter? A chemical exclusively made by neurons/glia.
What do glia do? Regulate content in the extracellular space. Removes NTs; can produce NTs of their own.
What are the axon hillock and the axon terminal? The right angle at the axon leaving the soma. The end of the axon.
This post is like a skydive from the classic high school course. Science beyond high school is all about asking questions and attempting to answer them. Some still don’t have answers. For example:
How does an organism priotize and intergrate sensory information to produce contextually approriate behavioural output?
The answer is we don’t know! That’s the magic of studying neuroscience, and science in general. It’s okay to ask a question that stumps a professor for a day, or a research facility for a lifetime. That’s how we learn.