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Option A: Neurobiology & Behavior A2: THE HUMAN BRAIN USE THE INFO IN THE PRESENTATION TO COMPLETE A1 NOTES GUIDE INFORMATION TAKEN FROM: HL BIOLOGY 2 ND EDITION DAMON, MCGONEGAL , TOSTO, AND WARD BIOLOGY FOR THE IB DIPLOMA PREPARATION GUIDE WALPOLE How does the brain develop from the neural tube? • Anterior embryonic neural tube develops to become the brain • Nerve cells migrate to the outer edge of the neural tube and causes the walls to thicken • At 3 months in utero, the complete structure is in tact • Neural tube develops into entire brain and spinal cord • Rapid growth continues after this point • Fibers of the nervous system form • After birth, growth continues … up to 4 times bigger by age 6 Brain Development Functions of different parts of the brain • You should be able to label a diagram showing the main areas of the brain Hypothalamus • Pituitary gland • Medulla oblongata • Spinal cord • Cerbellum • Cerebrum • Functions of different parts of the brain • You should be able to label a diagram showing the main areas of the brain Hypothalamus – controls ANS, coordinates endocrine & nervous systems by regulating pituitary gland secretions • Pituitary gland – posterior lobe stores & releases oxytocin and ADH from the hypothalamus; anterior lobe produces & secretes hormones (FSH, GH) • Medulla oblongata – brain stem, controls automatic and homeostatic activities (breathing, swallowing, heart rate) • Spinal cord • Cerebellum – coordinates movement, posture, balance • Cerebrum – coordination center for learning, memory, language, reasoning; receives info from the sense organs, and organizes motor functions • Spotlight on the Medulla • Regulatory Center Swallowing center: coordinates the muscles of the mouth, pharynx, and larynx • Breathing center: monitors level of carbon dioxide in the blood; if increased level the rate and depth of breathing increase • Cardioaccelerator center: under the influence of exercise heart rate will increase by direct stimulation of the cardioaccelorator center • The ANS • Autonomic Nervous System: controls involuntary processes in the body (swallowing, breathing, heart rate regulation) • 2 divisions of the ANS (both receive impulses from the medulla) • • Sympathetic Nervous System – emergency responses, fight or flight, is excitatory in effect; ntm = noradrenaline Parasympathetic Nervous System – controls non-urgent events, relaxed situations, is inhibitory in effect; ntm = acetylcholine Autonomic Nervous System The ANS examples Parasympathetic System: Eye: causes contraction of circular muscles of the iris to control the pupil Heart: heart rate slowed down, stroke volume reduced as body relaxes Digestive System: blood vessels are dilated, increasing blood flow to the digestive system The ANS examples Sympathetic System: Eye: causes contraction of radial muscles of the iris, dilating the pupil Heart: heart rate increased, stroke volume increased so that more blood can pump to the muscles Digestive System: blood flow to the digestive system is restricted as blood vessels constrict Pupil Reflex Cerebral Cortex Evolution in Humans • Cerebral cortex of a human brain is the outer layer of the 2 cerebral hemispheres known as grey matter • Controls functions like speech and decision making • Only found in mammals • Is folded so that its large surface area can fit into the skull Cerebral Hemispheres • Control higher order functions • Learning, memory, recall, speech and emotions • The right and left hemispheres contain different types of cells and different neurotransmitters • Different areas of the cerebral cortex also have different functions Left and Right sides of the brain • Right hemisphere receives info from the left side of the body • Left hemisphere from the right side of the body • Both hemispheres process information, but with different functions Broca’s area: speaking and writing Wernicke’s area: understanding of language Left Hemisphere: communication (speaking, sign language) Right Hemisphere: understanding words, recognizing faces, spatial reasoning Correlation between body and brain size • E:S Ration: Weight of the brain compared to weight of the body • E = brain weight S = body weight Powering Brain Activity • Very energy costly to fuel neurons and maintain membrane potentials of brain cells • 25% of the body’s metabolic energy requirement goes to the brain • Most of the energy supplied by aerobic respiration • Active regions of the brain use more energy than non-active regions • fMRI scanning can be used to identify areas of activity during different actitivies Brain imaging technologies • Neurobiology/Neuroscience: study of complex processing occurring in the nervous system • Animal studies – behavior studies • Brain injury studies – how different areas are affected when damaged by studying lesions • MRI Scanning – locates abnormalities • fMRI (functional magnetic resonance imaging) scans monitor brain activity from the blood flow to different areas Brain Death • That time when a physician has determined that the brain and brainstem have irreversibly lost all neurological function • In a coma, there are signs that can be measured • Testing for brain death: • • • • • • Movement of extremities Eye Movement Pupil Reflex Corneal reflex (blinking) Gag reflex Respiration response Check for understanding 1. Name 2 higher order functions and the area of the brain which controls the functions. 2. If a person suffered an injury to Broca’s area of the brain, what functions might be affected? 3. Draw and annotate a diagram of the human brain. 4. Explain why brain metabolism requires a large input of energy.