Organs are made up of specialized tissues, which are in turn made up of specialized cells. The brain is about 75% water, and the cells that form it are called neurons and glial cells. Interestingly enough, the brain is split into what is known as gray and white matter; gray matter consists of about 40% of the brain and contains approximately 100 billion neurons that collect and broadcast important signals. The other 60% is made of white matter, which is comprised of the neurons’ axons and dendrites–more on that in a moment–that are used to transmit said chemical signals.
According to the National Institutes of Health, our central nervous system, which contains the brain and spinal cord, makes use of two types of cells: neurons and glial cells. The neuron, however, is the star of the show.
Neurons function as a sort of cellular Hermes. They relay information among the brain’s various regions as well as the brain and the rest of the nervous system using both chemical signals and electrical impulses. All that we think, experience, and do is thanks to our neurons and the glial cells that support them.
Each neuron is made up of three distinct parts: a cell body, which houses the nucleus that contains DNA and controls the cell’s actions, and two appendages known as an axon and a dendrite. Axons and dendrites are found on opposite ends of the neuron; the former transmit messages from the cell, while the latter receive messages on behalf of the cell. Neurons carry out communication with one another with the help of chemicals known as neurotransmitters. Neurons send neurotransmitters across synapses, which are tiny gaps between axons and dendrites of adjacent neurons.
Neurons are broken up into three distinct classes:
- Motor neurons are in charge of voluntary muscle activities, like talking. They carry messages from the brain’s neurons to our muscles.
- Sensory neurons are in charge of shuttling information from our sensory organs–like our ears and eyes–to our brains.
- Interneurons refer to all other neurons; these types of neurons transfer impulses between other neurons.
Scientists consider neurons to be our body’s most diverse type of cell; there are actually hundreds of subtypes of neurons within the above three classes.
And what makes each of us unique in how we respond to every situation life throws at us is how our neurons communicate with one another.