There are three different types of neurons with three different shapes:
All neurons have a nucleus and soma. The nucleus creates proteins necessary for the cell to do its job, while the soma help produces energy for the nucleus the synthesize into proteins. All cells will have an axon coming off the nucleus, but the way they flow off changes depending on the neuron. Myelin Sheath wraps axons to help speed up signal transferring and eventually leads to the axon terminal, where the synapse happens.
Sensory neurons have axon terminals at one end and dendrites at the other that it uses to send and receive signals from receptors and has an axon that connects them together. A third section grows off of the axon holding the soma and nucleus.
Motor neurons are the neurons which will lead to an action happening. They have many dendrites coming from the nucleus to receive information from other cells through synapses, and very few axon terminals opposite the nucleus.
Interneurons also have large dendrites to accept information and do have long axons like the other neurons, rather they have multiple axons split off immediately from the nucleus and support many axon terminals so they can relay information faster to more neurons.
Neuron function:
From the beginning of the axons, there will be one section that receives an electrical signal. If this signal is strong enough to pass the threshold for an action potential to occur, then tunnels will open up to allow sodium ions into the axon, which happens because of the large concentration of positive ions outside the neuron, which means the sodium ions are repelled away into the axon, where the charge is less positive. Once inside, the next axon section gets alerted to open up its tunnels and receive its own sodium ions. While this is happening, new tunnels open up to allow potassium ions to escape, as the charge inside the axon went from a -70mV charge to about +30, which is the action potential. The potassium escapes from the positive charge through these tunnels, beginning the depolarization period. This period forces the sodium ions back out of the axon and potassium back in to reset the system and allow for a new signal to come through. This process is the reason that the signal doesn’t get shot backwards, as that section of the axon is not able to receive signals while in the depolarization period. This process takes a thousandth of a second and is done rapidly to end signals to the axon terminal for the synapse.
Synapse
The synapse happens between the end of an axon terminal, or at an axon terminal bulb, which bulges up to allow a better connection to the dendrite of another neuron. The axon terminal bulb has synapse vesicles floating around waiting for a signal. The tips of the dendrites have different receptors to receive signals that come from the opposing axon terminal bulb. Although there two structures are close to each other, they are not touching and and have a presynaptic gap between them. There are different types of neurotransmitters (NT’s) that get used in this process including but not limited to dopamine, serotonin, acetylcholine, GABA, and Glutamate.
The synapse begins when a signal is passed on by the axon terminal all the way to the tip. When this signal is received, the synaptic vesicles in the axon terminal bulb begin making their way to the presynaptic membrane, the closest point to the dendrite on the opposite side of the synaptic gap. Once the vesicles get there, they release NT’s into the gap. Using diffusion, the fact that the high concentration of NT’s will spread out from themselves naturally, NT’s are sent in all directions. Some of these NT’s will cross the synaptic gap and come into contact with the dendrite. Some of those attach to the proper NT receptor, which signals the next neuron to continue relaying the signal if that signal is strong enough to receive an action potential. Leftover NT’s that don’t attach to a receptor are collected by a NT recycler, which will break down NT’s and send them back to the axon terminal bulb that lets those NT’s be reused in the future.