A neurologist’s guide to your brain

During every second of every day, humans use their brains. Whether you’re sleeping, working, relaxing, or just staring at a wall, your brain is working.

But what is inside your brain? Which parts of this vital, yet remarkably complex, organ are responsible for your thoughts, dreams, actions, and bodily functions?

“The brain controls the entire body as well as processes that cannot be seen, like emotions and thoughts,” neurologist Dr. Huma Sheikh said in an interview. “The health of the brain affects all aspects of a person’s other health, including physical, emotional, and spiritual.”

While it would be nearly impossible to cover every single aspect of the brain, here is a basic overview of what’s inside of your brain and why it matters.

Why the brain matters 

To understand what is inside your brain, it’s helpful to have a visual reference for how big your brain actually is. One standard comparison often made is that your brain is about the size of two clenched fists put together, but this varies from person to person. 

“The brain is approximately 3 pounds, but men tend to have larger brains than women,” Sheikh said. “At birth, it is a little less than a pound and then grows to be its end weight, usually into the mid- to late 20s.”

Diseases, like forms of dementia like Alzheimer’s, or stroke can shrink the brain, too.

Because the brain is the human organ responsible for directing so many of the body’s processes, keeping the brain healthy is imperative to a person’s overall health.

“Having diseases in the brain will affect a person’s entire life, since the areas that are affected in the brain impact a person’s ability to function, whether it is moving, talking, or thinking,” Sheikh said.

What is inside your brain?

Regardless of the cartoon depictions you may remember from childhood, your brain isn’t just a big, wrinkly pinkish-gray lump floating around in your skull. The brain is actually composed of many different parts, and each is responsible for different processes and functions, which can impact the rest of the body in myriad ways.

• Cerebrum: “This is the topmost part of the brain and is the part that is the most developed in humans as compared to any other species,” Sheikh said. “The cerebrum has important functions like thought, executive control, language, facial and space recognition, and vision processing.”
• Cerebellum: “This is at the back and sometimes is referred to as the ‘smaller brain,’” Sheikh said. “It helps with coordination but receives a lot of the information from the cerebrum before it passes through to the brain stem.”
• Midbrain: “The midbrain is the top of the brain stem, and all the information from the cerebrum and cerebellum now will pass through the brain stem before going into the spinal cord,” Sheikh said. “The midbrain helps with movement, particularly movements of the eye, and in auditory and visual processing.”
• Pons: “The pons is similar to midbrain but also contains the specific nerves for hearing and taste,” Sheikh said.
• Medulla: The medulla is the lowest part of the midbrain and contains nerves that help with tongue and shoulder movement.

What does each side of your brain do?

While there are five main components of the brain, the brain is also divided into left and right hemispheres. There are specific functions that are controlled by each side of the brain, but sometimes signals must cross between these sides to control different functions or actions. 

“Some functions exist on both sides of the brain, but one side of the brain controls the opposite side of the body, for example, sensation and movement,” Sheikh said. “However, there are specifics to each side of the brain as well. Language for more than 99% of the population is on the left cerebrum, while something called sensory perception is on the right cerebrum, which helps to recognize your body as your own.”

How the brain connects to the body

To control bodily functions like moving, breathing, speaking, and more, the brain must communicate with the rest of the body. The brain sends signals to the rest of the body using neurons. Neurons are also used to send messages between different parts of the brain.

And neurons have a lot of work to do: There’s a lot of action taking place within the brain as different parts of the brain communicate with one another and then also with the rest of the body. The neurons fire rapidly throughout the brain and body to make these connections.

“Neurons are located in the brain and then continue into the spinal cord. There are then nerves that come off of the spinal cord and connect to muscles in our body to help us walk and move,” Sheikh said. “The neurons are able to speak with other neurons and muscles by releasing chemicals that attach to receptors on the receiving neuron or muscle.”

The communication that takes place between the brain and the body is a vital part of how people live, work, and exist in their day-to-day lives. When that connection is lost or diminished, it can have a tremendous impact on a person’s life.