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1 Introduction

Figure 1.34: The structure of a neuron.

All of these complex functions are performed with the help of a specialized cell, the

neuron. There are several different neurons, but they all have the same basic structure

(Figure 1.34). The cell body (soma) has two major extensions: dendrons that receive in-

formation from other neurons and axons that deliver information to the following neu-

rons. The incoming information from several neurons will be processed in the soma.

If the resulting membrane potential (see below) at the axon hillock is large enough, an

action potential (see below as well) will be sent to the following neurons via the axon.

The transmission is sped up because of the myelin sheath; basically, the potential can

jump from one node to the next.

A “potential” at a membrane is an imbalance of compounds at one side of the mem-

brane in comparison with the other side. This can obviously only happen if the mem-

brane itself is a good barrier and is very selective in what it lets through. This is true for

all membranes, but specifically for the membranes of neurons. This imbalance is called

“potential” because it is actually a form of energy – potential energy. This “potential”

has the potential to perform work, i. e. it is the driving force to balance out the com-

pounds on each side. In the case of the neuron membrane, the” potential” is specifically

an electrochemical potential, where not only the number of compounds, but the num-

ber of charges is in imbalance. That means that one side has more negative, the other

side more positive charges (Figure 1.35). This electrochemical potential at the neuron

membrane is generated by having different amounts of specific positive and negative

ions on each side, specifically, sodium, potassium, calcium, and chloride ions. To regu-

late this potential, the neuron membrane contains specific ion channels. Some of them