Because this book's main focus is on the day-to-day classroom applications of brain-based research, I will not attempt to provide you with a thorough description of the physical brain and all its functions. However, it is beneficial for teachers to have at least a general awareness of how the brain physically functions. This knowledge can help teachers understand their students' needs or reactions and may provide a physiological basis for certain instructional decisions. So, let's take a quick walk through the brain.

Imagine yourself in a time and place where plants cover the land, fish fill the sea, and reptiles are the only creatures you encounter. There are no computers, light bulbs, or even arrowheads. You do, however, see a lizard. Not a particularly cute critter and certainly not very intelligent. The lizard has a primitive brain that instinctually helps the animal survive. This animal's life revolves around vital functions: blood pumping, breathing, eating, reproducing, and so on.

A part of the human brain is lizard-like—the reptilian portion of our brains. Put on your galoshes and wetsuits because we're walking into the brain. The brain weighs only about three pounds and consists of lots of water, so it may get messy in here (Jensen, 1997). Our reptilian brain, or brain stem, is located at the base of the brain and is connected to the spinal cord (see Figure 1.1). The brain stem produces many of the brain's chemical messengers and controls the automatic, vital functions of the body that ensure our survival; it adjusts and maintains the body's heart rate, blood pressure, and breathing. The brain stem receives messages through the spinal cord from the five senses and reacts through the reticular activating system (RAS). This system filters out stimuli that are unimportant and sends the important messages to other parts of the brain or body for physical reaction or for conscious consideration (Wolfe, 2001). The RAS may make us unaware of the everyday aroma of our households; we are used to the smell of our own homes. However, when we walk into someone else's home, we may notice it has a distinct aroma. When you smell smoke, the RAS may even raise your heart rate and send a message to the conscious part of your brain, allowing you to think about fire and check your own safety status.

Figure 1.1. The Triune Brain Model

A related personal experience I have had with my sense of smell is directly correlated to my reptilian brain. During each of my three pregnancies, my sense of smell was dramatically heightened. For example, prior to being pregnant I played bingo and could not detect any odor emanating from the ink dabber unless I held it right under my nose. When I played bingo again when I was pregnant, not only could I smell the same dabber's odor from an arm's length, but the smell was so strong that it literally burned my nose. When I asked a neurologist at a seminar about this phenomenon, she explained it was my reptilian brain kicking in, protecting my unborn child from harm. Presumably a bingo dabber is of no threat. However, just as a mother lion's sense of smell is crucially important in detecting predators nearing her cubs, my brain's RAS was instinctually helping to protect me while in a more vulnerable state of pregnancy. Although I wasn't in danger of a predator attacking, the reptilian portion of the brain is essentially the same as it was back in the days of just lizards roaming the land. I was pregnant, so the reptilian portion of my brain heightened my sense of smell as an automatic protection function.

The next part of our journey continues to take us through the unconsciously functioning portions of the brain. The cerebellum, located behind the brain stem just above the very top of your neck, controls basic muscle movements and motor skills. The human cerebellum, like the brain stem, is not much different from the corresponding part of an animal's brain; it helps us walk or grasp or automatically remember how to perform other motor skills that we really don't need to think about. As we travel further up in the brain from the brain stem and cerebellum, we move beyond the lower, reptilian brain into the next level of evolutionary brain development—the limbic brain, which is the location of the limbic system(Howard, 2000). The limbic brain deals with eating, drinking, sleeping, hormones, and the emotions (Sprenger, 1999).

The final area of the brain is the forebrain, which contains the thalamus, the hypothalamus, the amygdala, and the neocortex, among other structures (see Figure 1.2). The thalamus helps control the body's vital functions and transfers some sensory information up to the cortex (the thinking part of the brain). The hypothalamus, located right below the thalamus, plays a role in regulating our bodies' normal physical functioning like temperature, sleep, hunger, sex drive, and fight-or-flight response to danger. The amygdala and hippocampus are also responsible for fight-or-flight responses. The amygdala works with the thalamus to decide what stimuli are dangerous and should be sent to the thinking part of the brain for processing. The hippocampus is one of the memory portions of the brain. It controls your immediate memories and decides what to do with them, including whether they should be acted on or sent to long-term memory (Wolfe, 2001).

Figure 1.2. The Forebrain

The last part of our walk through the brain takes us into the largest portion, called the upper brain or the neocortex. The cortex is the portion of our brains that strongly distinguishes us from animals. It is the part of the brain responsible for high-level thinking, problem solving, language, planning, vision, pattern recognition, and so on. It differs from the lower brain in that some of the neocortex's functioning is on a conscious level. When thinking through a problem, we know our brains are working. When we are reading a book or listening to someone, we are aware of the task at hand and are consciously putting effort toward our behaviors or actions (Jensen, 1997). The cortex consists of four main lobes with different functions (Wolfe, 2001).

• Frontal lobes. These lobes are located in the front of the brain and stretch up and back from the forehead. These lobes are responsible for all high-level, conscious thinking, such as contemplating choices and making decisions. The frontal lobes also control sensorimotor planning, such as positioning and moving fingers to thread a needle. This part of the brain has continued to develop and expand through evolution more than any other part of the human brain.
• Occipital lobes. These lobes are located in the back of the head and are responsible for processing visual information. They process information about objects, colors, motion, and distance, and connect this information with past experience and memories to provide meaning.
• Temporal lobes. These lobes are located above the ears and are responsible for processing auditory information. They distinguish differences in sound, pitch, and loudness and determine their significance.
• Parietal lobes. These lobes are located in the top, back portion of the brain and are responsible for spatial awareness and for processing and analyzing sensory stimuli. They also play a role in maintaining focus or attention.

At the meeting point of the occipital, temporal, and parietal lobes are Broca's Area and Wernicke's Area. These areas are responsible for producing and comprehending speech.

As we have journeyed through the brain, you may have noticed the 100 billion or so brain cells (neurons) we walked by on our route. These billions of neurons alone do not make the brain intelligent. It is when the neuron's dendrites (long tentacles that look like tree branches) reach out and connect to another neuron's dendrites that learning occurs. These connections, or synapses, are the pathways for new learning. When an infant is born, he or she may have trillions of brain cells. However, only the neurons that form connections to other brain cells survive (Jensen, 1998). Adults have fewer brain cells than newborn babies, but all of the adults' neurons are connected with dense branches of dendrites (Howard, 2000).

We have come to the end of our walk through the brain. Take off your wetsuit and galoshes and step back into your classroom now. Considering the physical and functional attributes of the brain, what are the implications for your classroom and students? Consider the fact that every brain, due to its different dendrite connections, experiences, and memories, is as different as each individual's fingerprints. This means that every student you will ever have in a class has different backgrounds, needs, abilities, and wants, and it's your job to see to it that all these different brains learn. Whew! And you thought you were tired from our journey through the brain. The thought of reaching all those unique brains is exhausting. Thankfully, they almost all have some similarities in how they learn best. Chapters 2 through 8 will provide samples and strategies of brain-compatible learning that you can immediately implement in your classroom to help your students grow billions of dendrite connections in their brains.