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Module 3 Brain’s Building Blocks DEVELOPMENT OF THE BRAIN • fact that your brain does not develop into a nose is because of instructions contained in your genes • Genes – chains of chemicals that are arranged like rungs on a twisting ladder – there are about 20,000-25,000 genes that contain chemical instructions that equal about 300,000 pages of written instructions – genes program the development of individual parts into a complex body & brain DEVELOPMENT OF THE BRAIN (CONT.) DEVELOPMENT OF THE BRAIN (CONT.) • Insert pictures of – Six week old brain – Mature brain STRUCTURE OF THE BRAIN • Human brain: – is shaped like a small wrinkled melon – 1,350 grams (less than 3 pounds) – pinkish-white color – consistency of firm Jell-O – Fueled by sugar (glucose) – 1 trillion cells divided into • glial cells • neurons STRUCTURE OF THE BRAIN (CONT.) • Glial cells • 3 Functions: – guide the growth of developing neurons – wrap around neurons and form an insulation to prevent interference from other electrical signals – release chemicals that influence a neuron’s growth and function STRUCTURE OF THE BRAIN (CONT.) STRUCTURE OF THE BRAIN (CONT.) • Neuron – a brain cell with 2 specialized extensions – one extension is for receiving electrical signals – the other extension is for transmitting electrical signals STRUCTURE OF THE BRAIN (CONT.) STRUCTURE OF THE BRAIN (CONT.) • Insert: video Main Parts of the Neuron, Psychology Digital Video Library 3.0. Debra Schwiesow, page 17 GROWTH OF NEW NEURONS • Can a brain grow new neurons? – canary brain • can grow about 20,000 neurons a day during the spring (learns new breeding song) – primate and human brain • researchers conclude that adult monkey and human brains are capable of growing relatively limited numbers of neurons throughout adulthood • Some new neurons play important role in continuing to learn and remember new things (hippocampus) GROWTH OF NEW NEURONS (CONT.) • Repairing the Brain – advances in stem research suggest the human brain may be able to grow more neurons – repair damages: • accident • disease • Alzheimer’s BRAIN VERSUS MIND • Mind-body Question – how complex mental activities such as • feeling • thinking • learning – can be explained by the • physical • chemical • electrical activities – of the brain PARTS OF THE NEURON • Cell Body – large egg-shaped structure that provides fuel, manufactures chemicals, and maintains the entire neuron in working order • Dendrite – branchlike extensions that arise from the cell body – receive signals from other neurons, muscles, or sense organs – pass these signals onto the cell body PARTS OF THE NEURON (CONT.) • Axon – a single threadlike structure that extends from and carries signals away from the cell body to neighboring neurons, organs, or muscles • Myelin Sheath – looks like separate tubelike segments composed of fatty material that wraps around and insulates an axon – prevents interference from electrical signals generated in adjacent axons PARTS OF THE NEURON (CONT.) • End bulbs or Terminal bulbs – located at extreme ends of the axon’s branches – miniature container that stores chemicals called neurotransmitters (used to communicate with neighboring cells) • Synapse – infinitely small space (20-30 billionths of a meter) – exists between and end bulb and its adjacent body organ, heart, muscles, or cell body ALZHEIMER’S DISEASE AND NEURONS • Alzheimer’s disease – excessive buildup of gluelike substances – gradually destroy neurons • Researchers recently discovered an experimental vaccine that may help stop the buildup of these gluelike, killer substances and they continue to search for other interventions NERUONS VERSUS NERVES • Reattaching Limbs – John Thomas • lost arms in farming accident • Transplanting a Face – Isabelle • face severely disfigured by a dog • received – new nose – lips – chin PERIPHERAL & CENTRAL NERVOUS SYSTEM • Peripheral Nervous System – made up of nerves that are located throughout the body, except in the brain & spinal cord • Central Nervous System – made up of neurons located in the brain & spinal cord PERIPHERAL & CENTRAL NERVOUS SYSTEM (CONT.) • Nerves – stringlike bundles of axons and dendrites that come from the spinal cord and are held together by connective tissue – carry information from the senses, skin, muscles, and the body’s organs to and from the spinal cord – nerves in the peripheral nervous system have the ability to grow or reattach if severed or damaged SENDING INFORMATION: ACTION POTENTIAL SEQUENCE – axon membrane has chemical gates that can open to allow electrically charged particles to enter or can close to keep out these particles – ions are chemical particles that have electrical charges – opposite charges attract and like charges repel SENDING INFORMATION: ACTION POTENTIAL SEQUENCE (CONT.) SENDING INFORMATION: ACTION POTENTIAL SEQUENCE (CONT.) • Resting state – the axon has a charge – the charge results from the axon membrane separating positive ions on the outside from negative ions on the inside SENDING INFORMATION: ACTION POTENTIAL SEQUENCE (CONT.) • Action potential – tiny electric current that is generated when the positive sodium ions rush inside the axon – enormous increase of sodium ions inside the axon causes the inside of the axon to reverse its charge – inside becomes positive and outside becomes negative SENDING INFORMATION: ACTION POTENTIAL SEQUENCE (CONT.) The Action Potential PLAY VIDEO SENDING INFORMATION: NERVE IMPULSE • Sending information – action potential is a tiny electrical current that is generated when the positive sodium ions rush inside the axon – the enormous increase of Na ions inside the axon causes the inside to reverse its charge – the inside becomes positive & the outside becomes negative SENDING INFORMATION: NERVE IMPULSE (CONT.) • All-or-None law – if an action potential starts at the beginning of the axon, the action potential will continue at the same speed segment to segment to the very end of the axon • Nerve impulse – nerve impulse is made up of 6 action potentials, with the first occurring at the beginning of the axon SENDING INFORMATION: NERVE IMPULSE (CONT.) TRANSMITTERS • A transmitter is a chemical messenger that transmits information between nerves and body organs, such as muscles and heart • Excitatory and Inhibitory – excitatory transmitters • open chemical locks and turn on neurons – inhibitory transmitters • block chemical locks and turn off neurons NEUROTRANSMITTER • Neurotransmitters – dozens of different chemicals that are made by neurons and then used for communication between neurons during the performance of mental or physical activities ALCOHOL • Alcohol (ethyl alcohol) – A psychoactive drug that is classified as a depressant, which means that it depresses the activity of the central nervous system ALCOHOL WHAT DOES ALCOHOL DO? • Alcohol affects the brain by imitating a naturally occurring neurotransmitter, GABA • GABA Neurons – GABA neurons have chemical locks that can be opened by chemical keys in the form of the neurotransmitter GABA • GABA Keys – alcohol molecules so closely resemble those of the GABA neurotransmitter that alcohol can function like GABA keys and open GABA receptors – when GABA neurons are excited, they decrease neural activity WHAT DOES ALCOHOL DO? (CONT.) • many people drink alcohol to feel less anxious and more relaxed • appears to be a biological link between alcohol and anxiety • deficiency in a specific brain protein is associated with high anxiety and excessive alcohol use NEW TRANSMITTERS • Number of well-known neurotransmitters, such as – Acetylcholine – GABA – Norepinephrine – Epinephrine – Dopamine – Serotonin NEW TRANSMITTERS (CONT.) • New – Endorphins (1970’s) • painkiller similar to morphine • decreases effects of pain during great bodily stress – Anandamide (1990’s) • similar to THC (active ingredient in marijuana) – involved with » memory » motorcoordination » emotions NEW TRANSMITTERS (CONT.) • Anandamide may help people regulate emotions, which would help them to better deal with anxiety and stress – Nitric oxide (mid-1990’s) • may be involved in regulating aggressive and impulsive behaviors REFLEX • Reflex – unlearned, involuntary reaction to some stimulus – neural connections underlying a reflex are prewired by genetic instructions REFLEX (CONT.) • Reflex sequence – sensors • sensors trigger neurons that start the withdrawal effect – afferent neurons • carry information from the senses to the spinal cord REFLEX (CONT.) – Interneuron • relatively short neuron whose primary task is making connections between other neurons – Efferent neuron • carry information away from the spinal cord to produce responses in various muscles and organs throughout the body REFLEX (CONT.) PARKINSON’S DISEASE • Parkinson’s Disease – includes symptoms of tremors and shakes in the limbs, a slowing of voluntary movements, muscle stiffness, problems with balance and coordination and feelings of depression – as the disease progresses, patients develop a shuffling walk and may suddenly freeze in space for minutes or hours at a time – Michael J. Fox PARKINSON’S DISEASE (CONT.) • Parkinson’s Disease – it is caused by destruction of neurons that produce dopamine – L-dopa is a medication that boosts the levels of dopamine in the brain – eventually the drug causes involuntary jerky movements – after prolonged use, L-dopa’s beneficial effect may be replaced by unwanted jerky movements EXPERIMENTAL TREATMENTS • Sterotaxic procedure – fixing a patient’s head in a holder and drilling a small hole through the skull – the holder has a syringe that can be precisely guided into a predetermined location in the brain EXPERIMENTAL TREATMENTS EXPERIMENTAL TREATMENTS EXPERIMENTAL TREATMENTS • Removing part of the brain – Thalamotomy (Michael J. Fox) • Brain Stimulation – electrodes placed into thalamus – patient controls amount of stimulus – helps reduce tremors EXPERIMENTAL TREATMENTS