Problem. When a neurone fires, it sends an electrical signal that jumps down the

Question

Problem. When a neurone fires, it sends an electrical signal that jumps down the axon via the nodes of Ranvier very rapidly. At a synaptic junction, chemical brownian diffusion signalling with receptor surface proteins is relatively slow and is often exploited by venoms and susceptible to toxins (on the plus side it's the reason a lot of medical drugs work.). It seems flawed for evolution to have selected for this rather than some alternative quicker and more direct electrical interface.

Question. Why are chemical synaptic interfaces used in higher organisms at the synaptic junction?

Explanation / Answer

This is the coolest part. Those synapses are the reason the brain is so complex! Basically you've got the first part right, the neurones are quicker and they transmit messages from one end to the other. The other thing you have to do is analyse and calculate. Signals from multiple neurones feed into a single neurone using a chemical synapse. Similarly the converse is true, a single neurone can feed multiple synapses. So when we for example walk, receptors monitoring our balance can feed this to our conscious and unconscious mind, but I'm grossly simplifying this. What our brain does is take hundreds and thousands of ports of information, with where the chemical synapse is and the type of synapse and the receptors and a million other things just slightly changing the information until it's perfect and then send that information a million ways however it likes.

The most important thing is this allows inhibition. Most of the brain uses inhibitory GABA rather than activating signals. Furthermore, the system uses the delay created. Different transmitters act for different durations and send a different volume of signal. An impulse is all or nothing, it's of a fixed amplitude, however a chemical signal can be fine tuned. Neurones can not only interact to inhibit themselves or other neurones to increase the resolution of a signal etc. Conversely a system of just physical connections allows little regulation, in fact it'd be practically a seizure.

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