Behind the Brain

How do neurons work? We know that they allow us to think, reason, and a bunch of really cool stuff. We also know that we have 100 billion neurons in our brain. But still, how do neurons functions?

Functions of a Neuron

A neuron has three different basic functions:

• To receive signals
• Determine what to do with the signals
• Communicate certain signals to target cells/neurons

These functions give us a valuable insight as to what parts of a neuron do what.

Parts of a Neuron

The neuron has 3 major parts; the dendrites, the axon, and the cell body (soma). Let’s start with the easiest, the soma.

Soma: The soma is just a normal cell body. It contains the nucleus of the cell, the mitochondria, the ribosomes, and all other normal cell organelles. This means that most proteins are produced in the soma. From the soma, there are several short protrusions that branch out (dendrites) and one seperate protrusion that is longer than all the others (axon).

Dendrites: Dendrites are responsible for receiving and processing incoming signals (the first two functions). These incoming signals are of two types; excitatory, or inhibitory. Excitatory signals make the neuron react/ fire a electrical signal, while inhibitory signals prevent the neuron from generating any signals.

Axon: The axon originates from the cell body. But not just from anywhere, like the dendrites. The axon originates from an area on the cell body known as the axon hillock. Hence, there is only one axon per neuron. The axon is responsible for the last function of a neuron, communicating with other cells through signals. Since each axon is responsible for a whole neuron’s outward communication, they have to be much faster than dendrites. Therefore, they are covered in myelin which insulates them. If you look closely at an axon, it will branch out into many branches. These branches, known as axon terminals (nerve terminals), make connections with the target cell.

Synapse: Axon terminals from the first neuron (presynaptic neuron) connect onto the dendrite or cell body of the target cell (postsynaptic neuron). This connection, called a synapse, is where information passes from the presynaptic neuron to the postsynaptic neuron. This information is mostly sent in the form of chemicals named neurotransmitters.

Types of Neurons

There are three types of neurons, all related to the three functions of a neuron; Sensory neurons, motor neurons, interneurons.

Sensory Neurons: Sensory neurons are responsible for perceiving your bodily condition, and your surroundings, and then communicating this information to other neurons.

Interneurons: Interneurons receive information from either a sensory neuron or another interneuron, and pass that information to a motor neuron, or another interneuron.

Motor Neurons: Motor neurons receive information from interneurons and convey commands to other parts of the body such as muscles, organs, and glands.