Neuronal Growth Cones
We know that neurons connect to each other, but how do they find each other to make connections? How do they know which connections are the right ones? Growth cones are the part of the neuron (from the axon which has to make connections) that grow outward to seek out other neurons and make those connections. They consist of actin (here shown in red) around the outside and microtubules (here shown in green) in most of the axon.
They grow by breaking down actin and adding pieces of actin to the leading edge- it’s a very dynamic process and is guided by signals in the extracellular space. For instance, other neurons can put out certain chemicals that will be in higher concentrations close to them (and more diffuse as you get further away, simply by the process of diffusion) and the growth cone is essentially attracted to where the concentration of that chemical is highest, leading the axon to another neuron. It’s a pretty cool process!
[Image from the Forscher Lab at Yale: Source]