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Chapter 3: Biology and Behavior Case Study: The Brain of Phineas Gage Section 1: The Nervous System Section 2: The Brain: Our Control Center Case Study: The Brain of Phineas Gage Phineas Gage was injured in a railroad accident in 1848. He suffered a brain injury that changed his personality. The Accident and the Aftermath • Gage was struck in the head by an iron bar. The bar rammed through Gage’s brain and out the top of his head. • Gage recovered from the physical effects of the wound, but his personality was altered Studies on Gage’s Skull • After Gage’s death, his family donated his skull to a museum. • Studies showed that the rod severely damaged an area in the brain related to personality. • Other studies found similar changes after injuries to the same part of the brain. Section 1 at a Glance The Nervous System • The nervous system functions as a communication system for the body. Messages are transmitted by neurons to axons and dendrites. • The nervous system is made up of the central nervous system and the peripheral nervous system, which transmits messages between the central nervous system and all parts of the body. Main Idea: The nervous system contains billions of cells called neurons. Neurons communicate with one another through the central and peripheral nervous systems. Reading Focus • • • • What are neurons, and how do they work? How do neurotransmitters work as chemical messengers? What does the central nervous system control? How is the peripheral nervous system structured? Neurons The nervous system has two parts. The nervous system consists of the brain and cord. The nervous system is made up of nerve cells that send messages between the central nervous system and other parts of the body. Nerve cells are called . Components of a Neuron • The produces energy that fuels the neuron’s activity. • receive information from other neurons and pass the message through the cell body. • An transmits information away from the cell body. Components of a Neuron (con’t) • is a white, fatty substance that covers the axon, insulating and protecting it. The myelin sheath helps to speed up the work of neurons. • Axon branch out at the end of the axon. The Communication Process • Messages are sent from the axon terminals of one neuron to the dendrites of another neuron. • In order for this process to happen, the message must cross a • A synapse is a between the axon terminals of one neuron and the dendrites of another. • Messages travel in only one direction. Messages – enter the dendrites – travel through the cell body and axon to the axon terminals – cross the synapses to the dendrites of other neurons Neurotransmitters: The Body’s Chemical Messengers • Neurons send messages across synapses through the of neurotransmitters. • Neurotransmitters are chemicals that are stored in in the axon terminals. • A neuron , or sends a message, by releasing neurotransmitters. – The message is converted into an electrical that travels through the neuron. – The message is transmitted to the next neuron by other neurotransmitters until the message arrives at its destination. • There are several kinds of neurotransmitters. – Acetylcholine is involved in the control of muscles and in learning and memory. – is involved primarily in motor behavior. The Central Nervous System • The central nervous systems consists of the neurons of the spinal cord and the • The spinal cord is a column of from the brain down the back. about as thick as a that extends • The spinal cord transmits messages between the brain and the muscles and glands in the body. • The spinal cord sends messages to specific muscles. • The spinal cord is involved in spinal reflexes. The Peripheral Nervous System 1. The Somatic Nervous System The somatic nervous system transmits messages to the central nervous system. • It carries messages from the voluntary muscles and sense organs. • It is activated by touch, pain, changes in temperature, and changes in body position 2. The Autonomic Nervous System • The autonomic nervous system regulates the body’s heartbeat, breathing, digestion, and blood pressure. functions, such as • It has two divisions. • The sympathetic nervous system reacts to • The parasympathetic nervous system restores peace to the body’s systems Section 2 at a Glance The Brain: Our Control Center • The brain is composed of three major sections: the hindbrain, the midbrain, and the forebrain. The cerebral cortex is the part of the brain that controls thinking, memory, language, emotions, complex motor functions, perceptions, and much more The Brain: Our Control Center Main Idea The human brain has many parts that work together to coordinate body movement, create thought and emotions, and shape behaviors. Reading Focus • • • • What were some of the early beliefs about the brain? What are the parts of the brain, and how do they function? How is the cerebral cortex divided? Which methods do scientists use to study the brain? Early Beliefs About the Brain • In ancient times, people did not attribute human psychological processes such as thinking to the working of the brain. • Instead, people widely believed that the body was inhabited by • Ancient Egyptians believed that a and regulated behavior. • The Greek philosopher heart. person dwelled within the skull thought that the soul resided in the • Today we recognize that the mind, or consciousness, dwells within the brain. Parts of the Brain The Hindbrain • The is involved in heart rate, blood pressure, and breathing. • The regulates body movement, attention, sleep, and alertness. • The is involved in balance and coordination. The Midbrain • Areas within the midbrain are involved in • Contains part of the reticular activating system, which is important for attention, sleep, arousal, and The Forebrain • The serves a relay station for sensory stimulation. • The is vital to the regulation of body temperature, the storage of nutrients, and various aspects of motivation and emotion. It is also involved in hunger, thirst, sexual behavior, caring for offspring, and aggression. • The system is involved in learning and memory, emotion, hunger, sex, and aggression. • The makes up about percent of the brain’s weight and is where most conscious and intellectual activities take place. • The cortex is the outer layer of the brain. It is the part that thinks, and it also deals with memory, language, emotions, complex motor skills, perception, and more. The Cerebral Cortex • The cerebral cortex has a left side and right side. • Each side is called a • The corpus callosum is the structure that connects the two hemispheres. • Information received by one side of the body is transmitted to the hemisphere of the brain. • Each hemisphere is divided into four parts: – frontal lobe – parietal lobe – temporal lobe – occipital lobe Senses and Motor Behavior • The lobe is the primary visual area of the cerebral cortex. • The cortex. lobe is the hearing, or auditory, area of the cerebral • Messages received from the skin’s sensory receptors are projected to the sensory cortex in the lobe. • These sensations include warmth, cold, touch, and pain. Association Areas • The association areas of the cerebral cortex shape information into something • The association areas in the center. lobes function as the brain’s executive • Association areas provide the core of the memory. • The frontal region of the brain thus retrieves visual, auditory, and other kinds of memories. • Other association areas make possible the psychological functions of language. Language Abilities • For nearly all right-handed people, language functions are based in the hemisphere. • Language functions are also based in the left hemisphere of about two out of three left-handed people. • Wernicke’s area connects sounds and sights. When this area is damaged, people find it difficult to understand • area is involved in speech. When this area is damaged, people speak slowly and use simple sentences. Left and Right Hemispheres • The hemisphere is usually more involved in logic, problem solving, and mathematical computation. • The hemisphere is more concerned with imagination, art, feelings, and spatial relations. Split-brain operations have taught psychologists much of what they know about left- and right-hemisphere functioning Methods of Studying the Brain Accidents • Researchers are able to learn how the brain is related to psychological functions through the study of brain damage due to accidents. Electrical Stimulation • Electrical stimulation of the brain has shown that specific areas are associated with specific types of sensations. • It is not a reliable research tool Lesions • Scientists can study a brain by cutting, removing, or destroying parts of it. • This method is used on laboratory animals. Electroencephalogram • The EEG is a device that records electrical activity of the brain. • EEG readings can help diagnose certain psychological disorders and to help locate tumors. Brain Imaging • Brain imaging can provide information about – brain damage – cancers – difficult surgeries • Brain imaging techniques include – CAT scans – MRI scans – PET scans – fMRI scans