Introduction to the Brain

The Brain Is the Boss

When you're taking a big math test, you know that your brain is hard at work. But your brain is doing a lot more than just remembering formulas. Those sweaty palms you get as the test starts? That's your brain at work. The relief you feel when you know an answer's right? That's your brain too. And yes, your brain is even in charge when you take a minute to daydream about the big party on Friday night.

The brain is like a computer that controls the body's functions, and the nervous system is like a network that relays messages to parts of the body.

The brain may simply be the bossiest part of the body: It tells virtually every other part of your body what to do, all the time, whether you're aware of it or not. It controls what you think and feel, how you learn and remember, and the way you move. It also controls things you might not think about — like the beating of your heart and whether you feel sleepy or awake.

The Brain & Nervous System in Everyday Life

If the brain is like a central computer that controls all the functions of your body, then the nervous system is like a network that sends messages back and forth from the brain to different parts of the body. It does this via the spinal cord, which runs from the brain down through the back and contains threadlike nerves that branch out to every organ and body part.

When a message comes into the brain from anywhere in the body, the brain tells the body how to react. For example, if you accidentally touch a hot stove, the nerves in your skin shoot a message of pain to your brain. The brain then sends a message back telling the muscles in your hand to pull away. Luckily, this neurological relay race takes a lot less time than it just took to read about it!

How the Brain Works

Considering everything it does, the human brain is incredibly compact, weighing just 3 pounds. Its many folds and grooves, though, provide it with the additional surface area necessary for storing all of the body's important information.

The spinal cord, on the other hand, is a long bundle of nerve tissue about 18 inches long and ¾ inch thick. It extends from the lower part of the brain down through spine. Along the way, various nerves branch out to the entire body. These make up the peripheral nervous system.

Both the brain and the spinal cord are protected by bone: the brain by the bones of the skull, and the spinal cord by the set of ring-shaped bones called vertebrae that make up the spine. They're both cushioned by layers of membranes as well as a special fluid. This fluid helps protect the nerve tissue, keep it healthy, and remove waste products.

The brain is made up of three main sections: the cerebrum, the cerebellum, and the brain stem.

The Brains Parts

The cerebrum contains the information that essentially makes us who we are: our intelligence, memory, personality, emotion, speech, and ability to feel and move. Specific areas of the cerebrum are in charge of processing these different types of information. The cerebrum has right and left halves, called hemispheres, which are connected in the middle by a band of nerve fibers (the corpus collosum) that enables the two sides to communicate. The two sides may look similar, but they have many different functions.

The cerebellum — also called the "little brain" because it looks like a small version of the cerebrum — is responsible for balance, movement, and coordination.

The brain stem takes in, sends out, and coordinates all of the brain's messages. It is also controls many of the body's automatic functions, like breathing, heart rate, blood pressure, swallowing, digestion, and blinking.

How the Nervous System Works

The basic functioning of the nervous system depends a lot on tiny cells called neurons. The brain has billions of them, and they have many specialized jobs. For example, sensory neurons take information from the eyes, ears, nose, tongue, and skin to the brain. Motor neurons carry messages away from the brain and back to the rest of the body.

All neurons relay information to each other through a complex electrochemical process, making connections that affect the way we think, learn, move, and behave.

Intelligence, Learning, and Memory

When you learn things, messages travel from one neuron to another, over and over. Then the brain creates connections (or pathways) between the neurons, so things become easier and you can do them better and better.

In children, the brain is highly adaptable. In fact, when one part of a child's brain is injured, another part may learn to take over some of the lost function. But as we age, the brain has to work harder to make new neural pathways, making it more difficult to master new tasks or change established behavior patterns. That's why many scientists believe it's important to keep challenging your brain to learn new things and make new connections — it helps keep the brain active over the course of a lifetime.

The Senses

Your eyes may watch as your best friend walks toward you — but without the brain, you wouldn't even recognize her. Pepperoni pizza sure is delicious — but without the brain, your taste buds wouldn't be able to tell if you were eating pizza or the box it came in. None of your senses would be useful without the processing that occurs in the brain. Our senses let us identify and respond to stimuli. A stimulus is a change in the environment like a loud sound.

· Sight. Sight probably tells us more about the world than any other sense. Light entering the eye forms an image on the retina. The retina transforms the light into nerve signals for the brain.

· Hearing. Every sound we hear is the result of sound waves entering our ears and causing our eardrums to vibrate. These vibrations are then transferred along the tiny bones of the middle ear and converted into nerve signals.

· Taste. The tongue contains small groups of sensory cells called taste buds that react to chemicals in foods. Taste buds react to sweet, sour, salty, and bitter. Messages are sent from the taste buds to the areas in the brain responsible for processing taste.

· Smell. Olfactory cells in the mucous membranes lining each nostril react to chemicals we breathe in and send messages along specific nerves to the brain — which, according to experts, can distinguish between more than 10,000 different smells. With that kind of sensitivity, it's no wonder research suggests that smells are very closely linked to our memories.

· Touch. The skin contains more than 4 million sensory receptors — mostly concentrated in the fingers, tongue, and lips — that gather information related to touch, pressure, temperature, and pain and send it to the brain for processing and reaction.

Why we have a nervous system

The nervous system keeps us alive in many different ways. First, the automatic things the brain does –like beating your heart or digesting your food – maintain homeostasis. Homeostasis is the property of your body to remain relatively constant. Examples of this are like your body temperature, or your pretty constant heartbeat. Sometimes it may be a little higher or lower, but it’s always about the same.