Guide to Playing Mozak

Types of Neurons — Spiny/Aspiny

The goal of this project is to learn all the different cell types in the brain, but we already know a lot. For example, most neurons fall into two main categories: spiny and aspiny. Learning the difference between a spiny and aspiny neuron will help you trace more accurately!

Spiny Neurons

A characteristic of all spiny neurons is that their dendrites have small projections called dendritic spines. Spines usually contain a synapse with the axon of another neuron, and having lots of spines increases the surface area available for a neuron to make synapses with lots of other neurons. You do not need to trace spines! Here is an example image to help you identify dendritic spines:

Spiny neurons generally have a “pyramidal” shape, which means they have one longer dendrite that travels towards the surface of the brain. The longer dendrite is called an apical dendrite (all the others are called basal dendrites). It is very common for the axon to exit the soma opposite the apical dendrite in spiny neurons. Here are some images to help you identify the pyramidal shape of spiny neurons and an apical dendrite:

The apical dendrite and its branches are in pink. The axon is in red, notice its location relative to the apical dendrite. Finally, can you see the pyramid shape the neuron has?

Aspiny Neurons

Aspiny neurons, by contrast, tend to have smooth dendrites. They still have synapses with the axons of other neurons, but their synapses are on the main shaft of their dendrites. Here is an example image of a smooth dendrite from an aspiny neuron:

Aspiny neurons also have lots of variety in their shape. Because of their smooth dendrites and the fact that their axon can exit the soma from any direction (or even from a distal dendrite) it can be much more difficult to figure out which neurite is the axon for aspiny neurons.


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