Neurons, Glia & Synapses

The human brain—three pounds of soft tissue—runs the show. It thinks, feels, moves, remembers, and dreams. Every thought you’ve ever had, every song stuck in your head, every philosophical spiral at 2 a.m.—all arise from a vast electrical web of cells talking to each other. This communication network is built from three key players: neurons, glia, and synapses. Together they form the biological internet of the nervous system.

The Neuron Doctrine and the Birth of Synapses

Once upon a time, scientists thought the brain was a single continuous net of tubes—one big undifferentiated blob. Enter Santiago Ramón y Cajal, a 19th-century Spanish neuroscientist armed with a microscope, a paintbrush, and obsessive curiosity. Peering into the stained jungle of the brain, he realized neurons were separate cells that communicated across tiny gaps. This radical insight became the neuron doctrine. Later, Sir Charles Sherrington confirmed those microscopic gaps actually did the talking—coining the term synapse. And just like that, the concept of brain connectivity was born.

The Star Performers: Neurons

Anatomy of a Neuron: By Rebecca Neisler

Neurons are the Beyonce performers of the nervous system—moody, high-energy, and utterly indispensable. Each one receives information, decides what to do with it, and passes it along through an electrochemical relay. Collectively, they form elaborate circuits that control everything from your heartbeat to your existential dread.

These circuits fire via action potentials—quick electrical surges that race down a neuron’s axon. When they reach the terminal, the signal transforms into chemistry: neurotransmitters spill into the synaptic cleft, cross the gap, and trigger the next cell. Think of it as Morse code in molecules.

Anatomy of a Neuron

Despite their diverse shapes and sizes, neurons share some key features. They have a central body (soma) containing the usual suspects for cellular function, like energy-producing mitochondria and protein-building ribosomes.

However, what sets neurons apart are their specialized structures for information processing. These distinctive parts can be grouped into four main zones. Each zone is specific in how neurons gather information, make decisions, and communicate with others.

Different Kinds of Neurons

By function:

Motor neurons: Command muscles and glands—your body’s movers.

• Sensory neurons: Detect stimuli from the world—light, sound, touch, taste.

• Interneurons: The behind-the-scenes operators, linking everything together in the brain and spinal cord.

By shape:

• Multipolar: One axon, many dendrites—the most common.

• Bipolar: One dendrite, one axon—often found in sensory systems like vision.

• Unipolar: A single process branching in two—ideal for fast relay of touch signals.

Glial Cells: The Unsung Heroes

If neurons are the rock stars, glia are the road crew keeping the stage lights on. They outnumber neurons and perform all the unglamorous but essential tasks: feeding, cleaning, insulating, and maintaining homeostasis.

Despite their low profile, glial cells are fundamental to brain function—and they keep being born throughout life, unlike neurons.

Types of Glia:

• Astrocytes: Star-shaped multitaskers that regulate nutrients and clean up waste.

• Microglia: The brain’s immune defense—janitors and bodyguards in one.

• Oligodendrocytes (CNS) & Schwann cells (PNS): The electricians, wrapping axons in fatty myelin to speed up signals. When this insulation breaks down, as in multiple sclerosis, communication falters.

The Adaptable Brain: Neuroplasticity

The brain isn’t a fixed machine—it’s a living, rewiring organism. Synapses form, dissolve, and strengthen based on what we experience. Learn a new skill, meditate, fall in love, or trip on LSD—and your neural circuits literally reshape themselves. This ability, called neuroplasticity, is what allows us to learn, recover, and reinvent ourselves.

Neurotransmitters: Chemical Messenger Communications

Neurons communicate with each other using chemical messengers called neurotransmitters. These messengers are stored in tiny sacs at the tip of the axon terminal called synaptic vesicles. Each vesicle at the axon terminal is like a message in a bottle, waiting for an action potential to pop the cork.

When the neuron gets a signal, these sacs open, releasing the neurotransmitter into a small gap (the synaptic cleft) between neurons. On the cleft’s other side, docking stations (receptors) await the neurotransmitter.

When the neurotransmitter connects with a receptor, it can either excite or calm down the receiving neuron (postsynaptic neuron), influencing whether it will send its signal onward.

Then, just as quickly, they detach and drift off—the brain’s version of ghosting. Different neurotransmitters carry different vibes: dopamine (motivation and reward), serotonin (mood and sensory modulation), glutamate (go, go, go!), and GABA (chill out). Each neuron listens to thousands of these simultaneous voices—a biochemical chorus that shapes consciousness.

Interestingly, there are many different types of neurotransmitters, each with its specific effect. The receiving neuron has many of these receptor docking stations, allowing it to simultaneously listen to various messages from other neurons. Some neurons can have tens of thousands of these connections, making the brain a complex communication web.

The Intricate Dance of the Nervous System

Altogether, the nervous system is a cosmic ballet of electricity and chemistry—billions of cells exchanging signals every millisecond to make reality cohere. Every perception, emotion, and insight emerges from this biological choreography. And as neuroscience keeps peeling back the layers, we’re reminded that the greatest mystery machine in the known universe is still the one behind our own eyes.

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Resources

Breedlove, S. M., Watson, N. V., & Rosenzweig, M. R. (2020). Behavioral Neuroscience, 9e. Sinauer Associates; Oxford University Press

Chen, I., & Lui, F. (2023). Neuroanatomy, neuron action potential. U.S. National Library of Medicine. https://www.ncbi.nlm.nih.gov/books/NBK546639/

Queensland Brain Institute, University of Queensland. (2024, October 22). Action potentials and synapses. https://qbi.uq.edu.au/brain-basics/brain/brain-physiology/action-potentials-and-synapses#:~:text=Synapse%20–%20The%20junction%20between%20the,which%20the%20two%20neurons%20communicate

Sheffler, Z. M., Reddy, V., & Pillarisetty, L. S. (2023). Physiology, neurotransmitters. U.S. National Library of Medicine. https://www.ncbi.nlm.nih.gov/books/NBK539894/

Swanson, L. W., Newman, E., Araque, A., & Dubinsky, J. M. (2017). The Beautiful Brain: The Drawings of Ramón y cajal. Abrams Books