Brain

What is the brain?

Your brain is a complex organ that regulates everything you do, like your senses, emotions, thoughts, memories, movement and behavior. It even controls body processes you don’t have to think about, like your breathing, body temperature and your heart rate. Everything that makes you uniquely individual comes from your brain.

Your brain is made up of many different parts, each with its own job. But they all work very closely together. This system works by sending and receiving information between nerve cells (neurons) that make up your brain. It then translates this information into a language that your body can understand, so you can function as expected.

Your brain connects to your spinal cord. They make up your central nervous system (CNS).

What is the brain’s function?

Your brain is responsible for the following functions:

• Automatic behaviors like breathing, heart rate, sleep and temperature control
• Fight-or-flight response (stress response)
• Keeping your organs working as expected
• Memories and emotions
• Movements (motor function), balance and coordination
• Sensory processing (vision, hearing, smell, touch and taste)
• Speech and language
• Thoughts and decision-making

Your brain’s job is to send, receive and process signals sent through your central nervous system. These signals are messages that carry information from your five senses (sight, smell, sound, touch and taste). Your brain also identifies signals from inside of your body, like pain, temperature or how fast your heart is beating. It interprets or translates this information so you can understand and associate meaning with what goes on around you.

When does the brain stop developing?

The majority of your brain development happens between birth and your teenage years. But your brain needs time to mature. It’ll continue this process through your mid to late 20s. One of the last parts of your brain to develop and mature is the prefrontal cortex. This part of your brain helps you make decisions, prioritize tasks and regulate your emotions.

What are the main parts of the brain?

Your brain has three main parts:

• Cerebrum. Your cerebrum interprets your five senses. It regulates conscious actions that require thinking, like your speech, memory, behavior, personality, movement, reasoning and judgment. It’s the largest part of your brain, divided into two halves: the left and right hemispheres. The two halves connect by nerve fiber bundles (white matter) called the corpus callosum.
• Cerebellum. Your cerebellum maintains your balance, posture, coordination and fine motor skills. It’s a small, half-circle shape that’s located in the back of your brain around your brainstem.
• Brainstem. Your brainstem regulates many automatic body functions. You don’t consciously control these functions, like your heart rate, breathing, sleep and wake cycles, and swallowing. Your brainstem is in the lower part of your brain. It connects the rest of your brain to your spinal cord.

A bony structure called your cranium surrounds your brain. Your cranium is part of your skull. Your brain floats in a liquid called cerebrospinal fluid (CSF). All the bones of your skull and CSF protect your brain from injury.

Between your brain and skull, you have three layers of tissue called the meninges:

• Dura mater. The outermost layer lines your cranial vault.
• Arachnoid membrane. The middle layer has a thin layer of tissue that covers your entire brain.
• Pia mater. The innermost layer contains blood vessels that run into your brain’s surface.

Your brain has 12 cranial nerves. Nerves carry messages by sending electrical impulses back and forth between your brain, organs and muscles. Information from your body passes through your nerves to your brain and from your brain to the rest of your body.

Other important parts of your brain include:

• Amygdala. Part of your limbic system and located in your temporal lobes, it helps you regulate your emotions, especially fear.
• Basal ganglia. Deep within your cerebrum, these structures regulate your movement.
• Hippocampus. This small structure in your temporal lobes is responsible for your memory and learning.
• Thalamus. Sitting above your brainstem, this is the switchboard to your central nervous system. It relays sensory information to your cerebral cortex from the rest of your body.
• Hypothalamus. Just below your thalamus, the hypothalamus regulates hormones and autonomic functions like hunger and thirst.
• Pituitary gland. Below the hypothalamus, the pituitary gland regulates hormone activity.
• Pineal gland. In the back of your corpus callosum, this gland regulates your sleep and wake cycles.

What are the lobes that make up your brain?

Your cerebrum is split into hemispheres (sides). On each side, there are four lobes (sections) with different functions:

• Frontal lobes. Located in the front part of your brain, behind your forehead, this is the largest lobe. It controls voluntary movements, social understanding, thinking and learning, and more.
• Occipital lobes. Located in the back of your brain, this lobe allows you to process and interpret visual information from your eyes.
• Parietal lobes. Near the upper back of your brain, this lobe receives and interprets signals from other parts of your brain so you can understand your environment and the state of your body.
• Temporal lobes. On the side of your head near your ears, this lobe helps you retrieve memories and understand language and emotions.

What is the gray and white matter in the brain?

There are two tissues in your brain known as gray and white matter. They differ based on their color and function:

• Gray matter is the darker, outside section (the cerebral cortex) that helps you with your day-to-day functioning., like muscle control, using your senses, remembering something, experiencing emotions and speech.
• White matter is the lighter section below the gray matter that sends signals to different parts of your central nervous system to help you function.

You can compare gray matter to a computer. White matter is the cables for the computer.

How many brain cells does a human have?

There are close to 86 billion nerve cells (neurons) in the human brain and an equal amount of non-neuronal glial cells:

• Neurons send and receive electric and chemical signals.
• Glial cells help maintain your brain, form myelin (a fatty, protective substance found in white matter) and provide nutrition to your brain.

How much does the human brain weigh?

An adult human brain weighs, on average, about 3 pounds. When you’re born, it weighs about 1 pound and grows to about 2 pounds through childhood. The weight of your brain varies based on your sex and body size.

What conditions can affect the brain?

Since your brain is responsible for almost everything you do, brain conditions are common. There are many types of brain disorders and conditions that vary in severity. Some of the most common include:

• Alzheimer’s disease and dementia
• Amyotrophic lateral sclerosis (ALS)
• Autism spectrum disorder (ASD)
• Brain bleed
• Brain tumor
• Concussion
• Depression
• Epilepsy
• Multiple sclerosis
• Parkinson’s disease
• Stroke
• Traumatic brain injury

Depending on the type of condition, you may be born with it or acquire it. Signs and symptoms vary and could affect your mental health, movement, memory, thinking and speech, among other important functions.