brains and suchlike

Categories: uncategorized

Date: 01 March 2007 06:18:28

So as you may have picked up in the last post, I am in the middle of my neurology block at the moment. It is very interesting and also rather humbling. Brains and nervous systems are rather complicated.

Something that has helped a lot was the dawning moment when I realised that a single neuron (or sometimes two neurons joined head to tail) goes from the brain to the place where it's doing stuff. The analogy often used to describe a nerve (a bundle of axons = neuron tails) is that of a motorway - all the cars are on the same road, driving side by side but they're going to and coming from different places. But that doesn't work for my literal interpretation of a motorway.

On a motorway:
- cars driving in one lane can change into a different lane and back whenever they like
- there are about 3 lanes max
- cars can leave the motorway at a particular point from either direction
- the lanes going in a particular direction are all bunched together
- cars can overtake each other
- cars can start at any point and leave at any point

Whereas in a nerve
- the axon is the lane - there is no information jumping between lanes at a nerve level
- there are millions of lanes
- the lanes are grouped by destination/origin rather than direction
- there is no overtaking. And no tailgating (due to the refractory period where the axon repolarises after an impulse goes past)
- lanes only leave the motorway going away from the city (central nervous system) and only join going to the city. A car can't join on the outskirts of the city and drive out to the country. It can only go to the city.
- similarly a car can't leave the motorway on it's way to the city.

So clearly the definition of a motorway needs a bit of tweaking before it is analogous to a nerve.