“Neurons perform a couple of different kinds of computation. Some forms of computation are used in learning, but the most common form of neural computation is the summation of excitatory and inhibitory influences. This computation won’t seem very impressive to Dieter, because computers can and do carry out many more complex functions and do it faster. But because it is so simple, the computation is also fast for biological processes and that speed allowed Jeremy to act in time to catch my baseball. Now we recall that neurotransmitters cross the synaptic cleft and trigger a response on the post-synaptic neuron. This reaction typically arrives at the dendrites of the neuron, though sometimes it occurs on the soma or the axon itself. The impulse makes its way to the axon hillock, a structure I mentioned earlier.

“The axon hillock is the most sensitive area of the neuron. You might think of it as the most ticklish region where it is easiest to provoke a reaction. There are lots of ion channels there, so if a few of them open, it can trigger a chain reaction that generates an action potential.”