LESSON 4: BRAIN STRUCTURE AND FUNCTION

1 Chapter 1: Know Yourself Socrates LESSON 4: BRAIN STRUCTURE and FUNCTION LESSON 4: BRAIN STRUCTURE . AND FUNCTION THE TRIUNE BRAIN . An early description of the human BRAIN was conceived by MacLean that axon attempted to explain its STRUCTURE in terms of BRAIN stem how it has evolved. According to MacLean's cerebral hemispheres theory, three separate and distinct brains exist, cortex from oldest to more recent. As each BRAIN Neo? dendrite evolved, the older BRAIN was retained for its limbic system specialized functions , and the new BRAIN neural plasticity simply formed around it.

2 Neurons neurotransmitter MacLean's theory provides a simple, sensory flooding easy to understand concept of the human BRAIN . This description relates directly to sensory gating evidence about how the BRAIN actually works, synapse as you will see in the sections on BRAIN FUNCTION and Downshifting. INTRODUCTION The human BRAIN , top to bottom, has three parts: the neocortex mushrooming out at This LESSON introduces you to the most the top, the limbic system (below that), and marvelous and mysterious part of your the BRAIN stem (at the base).

3 Anatomy the human BRAIN . Many people never totally discover or exert the full potential of their BRAIN . In this LESSON you will explore current research on what the BRAIN is ( STRUCTURE ) and how it works ( FUNCTION ). Neocortex You'll learn practical ways to apply complex (thinking). concepts that will put you in control of your Limbic System own mind. (emotions). EVOLUTION OF THE HUMAN BRAIN BRAIN Stem (instincts). One way to look at the BRAIN 's STRUCTURE is based on the theory of evolution. The BRAIN stem, sometimes called the Only 100,000 years ago, the ancestors of reptilian BRAIN (R-complex), is considered to modern man had a BRAIN weighing only about be the oldest part of the BRAIN from an a pound, which is roughly a third of the evolutionary standpoint.

4 It follows then that weight of our current BRAIN . Most of this much of the processing of basic survival increased weight is because of a much larger needs (eating, breathing and the fight or cerebral cortex. Here most of the thinking flight response) occurs here. Fight or flight is that makes human beings such unique the common terminology for a complex set of mammals occurs. This tremendous growth is reactions to a perceived threat, really the an important aspect of the evolution of the organism's ability to go on red alert and human BRAIN .

5 Respond quickly. Many of the body's systems Unit 3: Foundations for Success 13. Chapter 1: Know Yourself Socrates LESSON 4: BRAIN STRUCTURE and FUNCTION respond in automatically in order to increase Here's an example. When you touch a the chance of survival when under attack. hot stove, you pull your hand away quickly. That activity does not take much thinking, The limbic system, once thought to be and it had better not take a lot of time! In fact, associated exclusively with emotion, is now your nervous system is designed to process known to process not only emotional response information like that automatically, with little but also a number of high-level thinking help from the neocortex.

6 functions , including memory. Think about getting burned. What The neocortex, sometimes called the information would be helpful to store long cerebral cortex, is believed by researchers to term about that experience? Maybe the size, have grown out of the limbic system at some shape, and color of the heat source will help time in human evolution. Though not exclu- you to avoid the problem in the future. But sively, the neocortex is where most higher- the how to of pulling away your hand is order and abstract thoughts are processed.

7 The best left to the quick reactions of nerves and two hemispheres of the neocortex also handle muscles. Given the BRAIN STRUCTURE presented input from our sensory systems, making in Triune BRAIN theory, which of the three connections between various stimuli, such as major regions is probably in charge of the associating what we see with what we hear. burn response? This makes comprehension possible, and is how we make it all meaningful. If you figured the BRAIN stem, you're pretty close. In fact, muscles can react to This newest part of our BRAIN , the nerve impulses without those impulses ever neocortex, also attaches feeling and value to traveling up the spinal cord to the BRAIN .

8 The stimuli it receives. When humans learn, the withdrawal reflex, where the finger is pulled STRUCTURE and chemistry of nerve cells in the away from the pain as muscles contract, is the neocortex are changed. simplest act that the nervous system can perform. It is automatic and unconscious; it The concept of making meaning is does not involve any higher-level thinking. explored further as we delve into learning styles and processing preferences in other DOWNSHIFTING. lessons. But first let's take a closer look at how the BRAIN functions , this time from top to Now let's look at a process we call bottom, and how it interacts with the rest of downshifting.

9 From the top to bottom view the body. just described, downshifting describes what occurs when information processing moves BRAIN FUNCTION (TOP TO BOTTOM) from the higher-level thinking regions of the BRAIN , the neocortex and even the limbic The BRAIN is vital to human under- system, down into the BRAIN stem and even standing and the ability to learn. Perhaps into the automatic responses of reflex. Why you've heard of higher level thinking skills. does this happen? Why give up the ability to This phrase refers to the level of information ponder and reflect and instead revert back to processing and response required by a partic- instinct and involuntary reflexes?

10 Fear and ular task. Some complicated tasks can require intimidation are two main reasons down- a high level of information processing. shifting occurs. 14 Unit 3: Foundations for Success Chapter 1: Know Yourself Socrates LESSON 4: BRAIN STRUCTURE and FUNCTION In the presence of perceived threat, processing information in many different survival becomes important and the BRAIN ways activates the whole BRAIN . discerns the need for speed. Like the burn example above, your nervous system is fine MAJOR BRAIN AREAS.