Regardless of the type of neuron, the structural features of a neuron are pretty consistent across the board. Despite the differences, I tend to think of a typical structure of a neuron as similar to that of a scorpion, as seen here, with the dendrites replacing the legs, the cell body replacing the thorax and abdomen of the scorpion and the axon replacing the tailpiece. Each neuron has a specific function, which I’ll be discussing in more detail in Action Potential: Electricity at Work.
There are several key elements in common to each neuron: dendrites, an axon, a cell body with a nucleus and an axon terminal: I’ll discuss them all further down.
There are also additional features such as Schwann cells (myelin sheaths) and Nodes of Ranvier. These two are particularly important for a reason which I’ll go into later, and the lack of these can lead to disease.
Alright, I’ve kept you waiting long enough, here is the structure of a typical neuron. This picture is of a multipolar neuron, but the features are the same regardless of type:
The functions of each of these sections are as follows:
Dendrites are branches which receive a signal from an adjacent neuron (via synapses, which I’ll discuss further in the page labelled Synapses) and pass the electrical signal toward the cell body (or soma) through conduction.
Cell Body (Soma)
The major part of the soma is the nucleus, which is responsible for the production of RNA (ribo-nucleic acid) from DNA (deoxyribose nucleic acid), which I’ll discuss in the page DNA and RNA: The Basics. The RNA in turn is translated into proteins.
Axons serve two main functions: to conduct action potentials from the cell body (which I’ll discuss in Action Potentials: Electricity at Work), and to release neurotransmitters. They are also responsible for the transportation of protein vesicles from the cell body to help maintain the structural integrity of the neuron.
The axon terminal is the final portion of the axon, and this is the intersection point between this neuron and the next. This section is the area where the synaptic cleft lies.
Myelin Sheath (Schwann Cell)
Myelin sheaths are basically mulitple layers of adipose tissue or fat; they act as an insulator along the axon. This structure is particularly important in ensuring the maximum speed of the message being spread from one neuron to the next, as the message actually ‘skips’ between the Schwann cells rather than being pushed along the whole length of the axon.
Nodes of Ranvier
The Nodes of Ranvier are the exposed parts of the axon i.e. parts of the axon not covered by the Schwann cells.
Other Structural Cells
Other cells that work in conjunction to help maintain structural integrity of the neurons are known as glial cells.