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Neurons, Hormones, and the Brain Chapter 4 Copyright © 2007 Pearson Education Canada 1 Chapter Outline • • • • • • The Nervous System: A Basic Blueprint Communication in the Nervous System Mapping the Brain A Tour through the Brain The Two Hemispheres of the Brain Two Stubborn Issues in Brain Research Copyright © 2007 Pearson Education Canada 2 The Nervous System: A basic blueprint • The central nervous system • The peripheral nervous system – Somatic nervous system – Autonomic nervous system Copyright © 2007 Pearson Education Canada 3 Organization of the Nervous System Copyright © 2007 Pearson Education Canada 4 The Central Nervous System • Brain • Spinal cord – A collection of neurons and supportive tissue running from the base of the brain down the centre of the back – Protected by spinal column Copyright © 2007 Pearson Education Canada 5 The Peripheral Nervous System • Somatic nervous system: the subdivision of the peripheral nervous system that connects to sensory and to skeletal muscles • The autonomic nervous system: the subdivision of the peripheral nervous system that that regulates internal organs and glands Copyright © 2007 Pearson Education Canada 6 The Autonomic Nervous System Copyright © 2007 Pearson Education Canada 7 Communication in the nervous system • • • • The structure of the neuron Neurons in the news How neurons communicate Chemical Messengers Copyright © 2007 Pearson Education Canada 8 Structure of a Neuron • Dendrites – receive information from other neurons and transmit towards the cell body • Cell body – keeps the neuron alive and determines whether it will fire • Axon – extending fibre that conducts impulses away from the cell body and transmits to other cells Copyright © 2007 Pearson Education Canada 9 Types of Neurons Copyright © 2007 Pearson Education Canada 10 Structure of a Neuron • Myelin Sheath – Fatty insulation that may surround the neuron’s axon Copyright © 2007 Pearson Education Canada 11 Neurons in the News • Neurogenesis – The production of new neurons from immature stem cells • Stem cells – Immature cells that renew themselves and have the potential to develop into mature cells Copyright © 2007 Pearson Education Canada 12 Stem-Cell Research • Embryonic stem cells appear most promising in developing treatments for cancers, organ and brain diseases (e.g., Alzheimer’s) • Currently have ethical debate over their use • New techniques try to extract them without harming the embryo • McGill team has had some success in transforming adult cells into brain tissue Copyright © 2007 Pearson Education Canada 13 How Neurons Communicate • Axon terminals release neurotransmitter • Neurotransmitter enters the synapse • Neurotransmitter binds to receptors that it fits Copyright © 2007 Pearson Education Canada 14 Action Potential • A brief change in electrical voltage that occurs between the inside and outside of an axon when a neuron is stimulated • This produces an electrical impulse Copyright © 2007 Pearson Education Canada 15 Chemical Messengers • Neurotransmitters • Hormones Copyright © 2007 Pearson Education Canada 16 Neurotransmitter • Chemical substance released by a transmitting neuron at the synapse and capable of affecting the activity of a receiving neuron Copyright © 2007 Pearson Education Canada 17 Major Neurotransmitters • • • • • • • Serotonin Dopamine Acetylcholine (ACh) Norepinephrine Gamma amino butyric acid (GABA) Glutamate Endorphins Copyright © 2007 Pearson Education Canada 18 Opioids and Substance P Copyright © 2007 Pearson Education Canada 19 The Endocrine System • Endocrine glands release hormones into the bloodstream • Hormones regulate growth, metabolism, sexual development and behaviour, and other functions Copyright © 2007 Pearson Education Canada 20 Hormones: Long Distance Messengers • Melatonin – Regulates daily biological rhythms • Adrenal Hormones – Involved in emotions and stress • Cortisol, epinephrine, and norepinephrine • Sex Hormones – Regulate development and functioning of reproductive organs • Androgens, estrogens, and progesterone Copyright © 2007 Pearson Education Canada 21 Mapping the Brain • Lesioning – Involves damaging and removing sections of brain in animals, then observing their effects – Some lesions are cased by accidents, traumas, or disease Copyright © 2007 Pearson Education Canada 22 Electroencephalogram (EEG) • A recording of neural activity detected by electrodes Copyright © 2007 Pearson Education Canada 23 Transcranial magnetic stimulation (TMS) • Involves delivering a large current through a wire coil on a person’s head • Also used to: – produce motor responses – temporarily inactivate an area of the brain – treat depression Copyright © 2007 Pearson Education Canada 24 Positron Emission Tomography (PET) • A method for analyzing biochemical activity in the brain, using injections of a glucose-like substance containing a radioactive element • Active areas have increased blood flow • Sensors detect radioactivity • Different tasks show distinct activity patterns Copyright © 2007 Pearson Education Canada 25 Magnetic Resonance Imaging (MRI) • Method for studying body and brain tissue • Magnetic fields align certain ions and compounds • When field is removed, these molecules release energy as radio waves • Computer calculates tissue density from radio waves • Provides clear, 3D images Copyright © 2007 Pearson Education Canada 26 A Tour Through the Brain • • • • • • • Brain stem Cerebellum Thalamus Hypothalamus and the pituitary gland Amygdala Hippocampus Cerebrum and lobes of the cerebral cortex Copyright © 2007 Pearson Education Canada 27 The Brain Stem • Pons – involved in sleeping, waking and dreaming • Medulla – responsible for certain automatic functions such as breathing and heart rate • Reticular activating system (or formation) – arouses cortex and screens incoming information Copyright © 2007 Pearson Education Canada 28 The Cerebellum • Regulates movement and balance • Involved in remembering simple skills and acquired reflexes • Plays a part in: – analyzing sensory information – solving problems – understanding words Copyright © 2007 Pearson Education Canada 29 The Thalamus • Relays sensory messages to the cerebral cortex • Includes all sensory messages except those from olfactory bulb Copyright © 2007 Pearson Education Canada 30 Hypothalamus and Pituitary Gland • Involved in emotions and drives vital to survival – fear, hunger, thirst, and reproduction • Regulates autonomic nervous system • Pituitary gland – small endocrine gland which releases hormones and regulates other endocrine glands Copyright © 2007 Pearson Education Canada 31 The Amygdala • Responsible for: – arousal – regulation of emotion – the initial emotional response to sensory information • Plays important role in – mediating anxiety and depression – emotional memory Copyright © 2007 Pearson Education Canada 32 The Hippocampus • Responsible for: – storage of new information in memory – comparing sensory information with what the brain expects about the world – enabling us to form spatial memories for navigating the environment Copyright © 2007 Pearson Education Canada 33 The Cerebrum • Largest brain structure • This upper part of the brain is divided into two cerebral hemispheres that are connected by the corpus callosum • In charge of most sensory, motor and cognitive processes • Surrounded by cerebral cortex, a collection of several thin layers of cells (grey matter) Copyright © 2007 Pearson Education Canada 34 Lobes of the Cerebral Cortex • Occipital lobes (visual cortex) • Parietal lobes (somatosensory cortex) • Temporal lobes – Memory, perception, emotion and auditory cortex – Left lobe, Wernicke’s area • Frontal lobes – Emotion, planning, creative thinking and motor cortex – Left lobe, Broca’s area Copyright © 2007 Pearson Education Canada 35 Lobes of the Cerebral Cortex Copyright © 2007 Pearson Education Canada 36 Phineas Gage • Gage was a railroad construction foreman • An 1848 explosion forced a steel tamping rod through his head • Others said he was “…no longer Gage…” • Lost his job and worked as a sideshow exhibit Copyright © 2007 Pearson Education Canada 37 The Two hemispheres of the Brain • The Split Brain: a house divided • The two hemispheres: allies or opposites? Copyright © 2007 Pearson Education Canada 38 The Corpus Callosum • Millions of myelinated axons connecting the brain’s hemispheres • Provides a pathway for communication between hemispheres • If surgically severed to treat epilepsy, hemispheres cannot communicate directly Copyright © 2007 Pearson Education Canada 39 Split-Brain Experiment Copyright © 2007 Pearson Education Canada 40 Split-Brain Experiment • Subjects were presented information to one or the other side of their brain • Patients identified verbally the pictures to the right (i.e., boy) • When asked to point to the face seen, the patients pointed to the left picture Copyright © 2007 Pearson Education Canada 41 The Two Hemispheres: Allies or Opposites? • Research on split-brain patients shows us: – Nearly all right-handed and the majority of lefthanded individuals process language mainly in the left hemisphere – Many researchers believe in left-hemisphere dominance – Others insist the right-hemisphere is important for spatial visual problem-solving, comprehending non-verbal sounds, and some language abilities Copyright © 2007 Pearson Education Canada 42 Two Stubborn issues in Brain Research • Where is the Self? • Are there “his” and “hers” brains? Copyright © 2007 Pearson Education Canada 43 Where is the Self? • Modern brain scientists explain the mind or soul in physical terms, as a product of the cerebral cortex – The mind is: • a series of independent brain parts dealing with different aspects of thoughts (Dennett, 1991) • a loose confederation of mental systems all working without conscious awareness (Gazzaniga, 1998; Roser & Gazzaniga, 2004) • Frontal lobes may play a critical role • Many still question the relationship between subjective experience and physical processes of the brain Copyright © 2007 Pearson Education Canada 44 Are There “His” and “Hers” Brains? • After analyzing 49 studies of sex differences in brain anatomy, researchers found small differences between the two groups and larger differences within groups • There do appear to be sex differences in lateralization of language. Males show lefthemisphere activation only; females, left and right • There also appear to be differences in amounts of grey matter: females have more Copyright © 2007 Pearson Education Canada 45 Gender & Language Laterality Copyright © 2007 Pearson Education Canada 46 What do “Differences” Mean for Behaviour? • These supposed differences are stereotypes • A brain difference does not necessarily explain behaviour or performance • Sex differences in the brain could be the result rather than the cause of behavioural differences • Use your critical thinking skills to evaluate all of the research! Copyright © 2007 Pearson Education Canada 47