The Master organ: our wrinkly Brain NEURONS: OUR OWN ELECTRICAL WIRES

Author: Daniel Zhou

Editors: Hwi-On Lee and Peggy Yang

Artist: Guanxin (Acey) Li

With personalized signaling pathways in each human, it becomes much more complicated than just figuring out “what triggers which” within the human body. As a result, neurons, the carrier for these signals, become much harder to understand after a basic understanding of their pathways

The human brain is made up of many little messengers in the brain called neurons as well as the physical support for neurons called glial cells. Billions of these individual neurons communicate together to help coordinate all the necessary functions of life, essential to every function in the human body

A neuron has 3 parts: dendrites, an axon, and a soma (cell bodies). First, the dendrites are where the neuron receives input from other neurons. Second, the axon is the output of the cell, where a neuron sends an electrical message called an action potential throughout the entire axon Finally, the soma is where the nucleus resides and where proteins are made to be transported throughout the axon and dendrites

Neurons communicate via action potentials and chemical neurotransmitters. Action potentials are nerve impulses or spikes. In the synapses, or spaces, between neuron cells, action potentials cause neurons to release chemical neurotransmitters This process of releasing neurotransmitters between the synapses is called neurotransmission. These chemicals then travel a tiny distance between the synapses of the neurons before reaching other neuron cells. Once the chemicals are received by the dendrites of another neuron, this neurotransmitter can either help excite or hinder the other neuron from discharging its own action potential Anytime a neuron spikes, these neurotransmitters are released from hundreds of its synapses resulting in communications between hundreds and thousands of other cells.

In the spinal cord, neuron cells can be further divided into three types: sensory neurons, motor neurons, and interneurons.

The Master organ: our wrinkly Brain

Sensory neurons are nerve cells that are activated by sensory input from the environment, meaning that the inputs that activate these neurons can be physical or chemical This corresponds to all five of our senses (sight, hearing, touch, taste, and smell) These types of neurons are mostly pseudounipolar, meaning that they have one axon that splits into two branches

The second type of neuron cell in the spinal cord is motor neurons. These neurons are a part of the spinal cord and are therefore a part of the central nervous system, which consists of the brain and the spine. Motor neurons connect to muscles, glands, and organs throughout the body, and they control all muscle movement by transmitting inputs from the spinal cord to the skeletal and smooth muscles Motor neurons can be further split into two types: lower motor neurons and upper motor neurons The lower motor neurons transmit signals from the spinal cord to the muscles while the upper motor neurons transmit signals between the brain and the spinal cord. These cells are multipolar, meaning that they each have one axon and several dendrites.

Finally, the last type of neuron cell in the spinal cord is the interneuron These neuron cells are the neuron cells between the motor neurons and sensory neurons They transfer signals to both types of neurons to help them communicate, as well as communicate between themselves. Like the motor neurons, these cells are also multipolar.

Despite what science has already discovered, our knowledge of neurons is still very limited There are tens or hundreds of other different neuron types in the brain that cannot be neatly categorized unlike those in the spinal cord They are much harder to classify due to how specialized the brain is compared to the spinal cord, but researchers are still trying to find a neat way to categorize all these cells.

For now, what we do know is that our neurons communicate through action potentials and chemical neurotransmitters Furthermore, there are many different types of neurons that are unique in their own way, but the three types that can be found in the spinal cord are sensory neurons, motor neurons, and interneurons.