Demystifying the Brain: Understanding its Major Structures and Functions

1. Chapter 3 Section 2 The Brain: Our Control Center Obj: Identify the major structures of the brain, and explain the functions of each structure.

2. Parts of the Brain The brain is divided into three sections: the hindbrain, the midbrain, and the forebrain. The hindbrain is the lower portion of the brain and is involved in many vital functions such as heart rate, respiration, and balance. The midbrain includes areas that are involved in vision and hearing. The forebrain, the front area of the brain, is involved in complex functions such as thought and emotion.

3. The Hindbrain The medulla is involved in vital functions such as heart rate, blood pressure, and breathing. The pons is located in front of the medulla and is involved in regulating body movement, attention, sleep, and alertness. The cerebellum is involved in balance and coordination. (if it gets injured, the person could walk unsteadily or occasionally fall down)

4. The Midbrain It’s located between the hindbrain and the forebrain, and is involved in vision and hearing. Contains the reticular activating system, which is important for attention, sleep, and arousal. Stimulation makes us alert. Some drugs reduce the activity of this system, thus affecting alertness and reaction time.

5. The Forebrain Four key areas are the thalamus, the hypothalamus, the limbic system, and the cerebrum. All are involved in complex thinking processes.

6. Thalamus – (Relay station) transmits sensory information, such as pain and input from the eyes, to the areas of the brain that interpret the information. • Hypothalamus – vital to the regulation of body temperature, the storage of nutrients, and various aspects of motivation and emotion. • Limbic system – involved in learning and memory, emotion, hunger, sex, and aggression. Damage can cause short-term memory loss, passivity, or severe aggression.

7. Cerebrum – comprises 70% of the weight of the brain. The wrinkled surface is the cerebral cortex, the outer layer of the brain. This is the part that thinks, deals with memory, language, emotions, complex motor functions, perception, and much more.

8. The Cerebral Cortex: What Makes Us Unique The cerebral cortex is composed of two sides – a left hemisphere and a right, with the corpus callosum dividing them. Information received by one side is transmitted to the opposite hemisphere of the brain. Each hemisphere is divided into four parts, or lobes: frontal, parietal, temporal, and occipital.

9. Senses and Motor Behavior The occipital lobe contains the primary visual area of the cerebral cortex. When light strikes the eye, neurons in this lobe fire, enabling us to see. Damage to this area can create the inability to recognize objects, or being unable to differentiate it from another object that is similar.

10. The hearing, or auditory, area is in the temporal lobe. Sounds are relayed from the ears to the thalamus to the auditory area. When this occurs, we hear sounds. if this area gets damaged, people may not recognize common sounds. Messages received from the skin go to the parietal lobe. Different neurons fire, depending on whether you have scratched your nose, touched a hot stove, etc. Neurons in the motor cortex fire when we move certain parts of our body.

12. Association Areas Much of the cerebral cortex is composed of areas that involve sensory and motor functions. Other areas, called association areas, shape information into something meaningful. They take information and put it all together to make sense. Example-take bunch of lines and turn it into a car. They are connected with sensory areas in the brain and can tap whatever sensory information is needed or desired; visual, auditory, and other kinds of memories and manipulates them.

13. Language Abilities Language functions are based in the left hemisphere of most people, whether left or right handed. Two key language areas are Broca’s area (controls the areas of the face used for speaking) and Wernicke’s area (pieces together sounds and sights). Damage to either area is likely to cause an aphasia, a difficulty with specific aspects of understanding or producing language.

15. Left Versus Right Hemisphere Left hemisphere is usually more involved in logic, problem solving, and math. The right is associated with imagination, art, feelings, and spatial relations. Although some differences do exist between the two, the hemispheres do not act independently of each other. Most of what we know about the two hemispheres is the result of a surgery that splits the two halves for severe cases of epilepsy. The surgery can have strange effects. Example; people may be able to describe verbally the objects they hold in their right hand but not what they hold in the left. This is due to the language side of the brain being on the opposite side of the body.

17. Methods of Studying the Brain • Accidents – brain damage from head injuries and other accidents. We’ve learned that which particular area is damaged may have a greater effect than the amount of the damage. • Electrical Stimulation of the Brain – This has shown that specific areas are associated with specific types of sensations (such as seeing light or feeling a tap on the arm) or motor activities ( such as walking).

18. Electroencephalogram – the electroencephalogram (EEG) is a device that records the electrical activity of the brain. Electrodes attached to the scalp with tape or paste detect small amounts of electrical activity called brain waves. • Scans – techniques where computers generate images of the brain from various sources of information. • CAT scans, a moving ring passes X-ray beams around and through the head. Computers measure the amount of radiation and piece together a 3-dimensional view.

19. MRI scan, a person lies in a very powerful magnetic field. Radio waves then cause parts of the brain to give off extra energy. This energy is measured from multiple angles and is translated by computer into a visual. • PET scan shows the activity of the brain rather than a snapshot of the brain at a given time. The person is injected with radioactive sugar. As the sugar reaches the brain, more of it is used where brain activity is greater. A computer image is generated based on the activity.