Want to learn about scientific topics without needing a PhD? Check out the Science Simplified blog from TESS Research Foundation! Dr. Tanya Brown, PhD, works with researchers to make science accessible and empower rare disease community members with scientific knowledge. Dr. Brown has over a decade of experience in neurodevelopmental research and is currently the Scientific Director for TESS Research Foundation. Please reach out to her at [email protected] if you have questions or comments.

Thank you to Sydney Wolfe for writing this story. Sydney recently graduated with a degree in neuroscience from WSU Vancouver. 

All about neurons!

Have you ever wondered how our brains make sense of the world? The answer lies in the billions of specialized structures in our brain called neurons.

Which systems in the body use neurons?

Neurons are the fundamental building blocks for learning, memory, and movement. They can be found in the central nervous system and the peripheral nervous system.

• The central nervous system comprises the brain and spinal cord and is responsible for forming thoughts and generating various actions throughout the body.
• The peripheral nervous system allows the central nervous system to send and receive information to and from all parts of the body.
  • The peripheral nervous system can be broken down further into the somatic and autonomic nervous systems:
    • Somatic nervous system: Voluntary actions (requiring conscious thought), like clapping your hands or running in a marathon.
    • Autonomic nervous system: Involuntary actions, such as the beating of your heart.

What are the different parts of a neuron?

To understand how neurons communicate, we must first learn about all the different components of a neuron! The main parts include the cell body (sometimes called the “soma”), dendrites, and the axon.

Visually, neurons are a lot like trees. You can think of the cell body as the bulky tree trunk, the dendrites as branches, and the axon as a long root that extends far beyond the tree. Neurons can have several dendrites (the branches) but only one axon (the trunk).

How do neurons communicate?

A conversation between neurons begins when the dendrite of a neuron detects a message from another neuron. Neurons communicate to each other like people, with the words varying in strength. Some words communicate a loud, clear message, while others communicate a weaker message, and some say “stop talking.” A neuron’s “words” are actual physical materials, called neurotransmitters, and some common ones include serotonin, dopamine, glutamate, and norepinephrine.

Once a dendrite receives a message, that message is moved from the dendrite down to the cell body.  After the cell body receives the message, it sends the info down the axon to the end of a neuron (the axon terminal). This message is known as an action potential. The action potential triggers the release of neurotransmitters in a gap between two neurons called the synaptic cleft. The type of neurotransmitter released determines the message.

Neurotransmitters bind to the neighboring neuron to activate (also known as exciting a neuron) or prevent communication (also known as inhibiting a neuron). When the first neuron “inhibits” another neuron, it is less likely that the second neuron will continue the conversation. Alternatively, “excitation” keeps the conversation going! Glutamate is the primary excitatory neurotransmitter in the brain and is thought to help our brain learn and form new memories.

So why do some neurons release inhibitory neurotransmitters that lower the chance that the conversation will continue, while other neurons release excitatory neurotransmitters increasing the likelihood that the conversation will continue? The brain actually requires a healthy dose of both types of neurons. While inhibition may seem like a negative concept, inhibitory neurotransmitters function in quieting the brain (for example, during sleep).

What are the different types of neurons?

The function and structure of neurons vary widely depending on what part of the brain they’re located in. Neurons can be broken up into three basic categories: motor, sensory, and interneurons.

• Sensory neurons are activated by the five basic senses: taste, touch, sound, sight, and smell. For example, the sensory neurons involved in smell are called olfactory sensory neurons.
• Motor neurons are in the brain stem, spinal cord, and motor cortex of the brain. They work by sending messages to our bodies to carry out movement.
• Interneurons (also called relay neurons) allow for communication between sensory and motor neurons. They are found in the brain and spinal cord (central nervous system). Many interneurons are used to generate reflexes (quick, unconscious responses). For example, the withdrawal reflex occurs when the body is exposed to painful or damaging stimuli, such as touching a hot stove. When this happens, a sensory neuron sends a signal to interneurons in the spinal cord. The interneurons will then send a signal to motor neurons, causing the withdrawal of your hand.

How do we study neurons?

We can study neurons in vivo,  ex vivo, or in vitro: 

• In vivo means that we are studying processes that take place in a live animal.
• Ex vivo is a process or experiment taking place outside of the animal.
• In vitro means studying isolated cells or molecules outside their normal biological environment. This often means studying cells in a dish.

There are multiple animal models used to study neurons, including zebrafish, mice, and rats. Zebrafish make great in vivo research animals because they have a very simplistic nervous system, which allows for easy visualization of neurons. On the other hand, rodents exhibit similar biological and behavioral characteristics to humans, making them suitable animals to use in neuron research. Scientists use mice and rats for both in vivo and ex vivo studies! Here is one example of an ex vivo technique using a rodent brain.

How does this relate to SLC13A5 Epilepsy?

Scientists are using multiple types of animal models to investigate SLC13A5 Epilepsy. There are mouse, fly, and zebrafish models of SLC13A5 Epilepsy that are used to investigate how neurons communicate and function with changes to SLC13A5. There are also cell culture models available so that scientists can study SLC13A5 Epilepsy neurons in a dish. Both animal and cell culture models are providing key information about the role of SLC13A5 for neurons.

Conclusion

Neurons are the fundamental building blocks that make up major parts of you! Like people, they communicate messages with each other to accomplish goals. Our brains are never stagnant and are subject to constant change. They can work together to form new memories and emotions, learn new concepts, move muscles, and more! Here are some key takeaways:

1. Neurons are the building blocks of the brain and have three main parts: the cell body, the dendrites, and the axon.
2. Neurons use neurotransmitters to communicate with each other. Some of these neurotransmitters are inhibitory and others are excitatory.
3. There are multiple models to study the role of SLC13A5 in neurons.