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 – __________________________________________ __________________________________________ __ – there are about 20,000-25,000 genes that contain chemical instructions that equal about _______ pages of written instructions – genes program the development of individual parts into a complex body & brain DEVELOPMENT OF THE BRAIN (CONT.) 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 – __________________________________ – 1 trillion cells divided into • _______________________ • _______________________ STRUCTURE OF THE BRAIN (CONT.) • Glial cells – 3 Functions: • ____________________________________ • ________________________________________ ________________________________________ • ________________________________________ ________________________________________ ________________________________________ STRUCTURE OF THE BRAIN (CONT.) • Neuron – a brain cell with 2 specialized extensions – one extension is for _____________ electrical signals – the other extension is for _______________ electrical signals 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 • ______________________ • ______________________ • _________________________ – can be explained by the • _____________________ • _______________________ • __________________________ – ______________________ PARTS OF THE NEURON • Cell Body – large egg-shaped structure that provides fuel, manufactures chemicals, and __________________________________________ __________________________________________ __ • Dendrite – branchlike extensions that arise from the cell body – __________________________________________ __________________________________________ __ – 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 – _______________________________________ – _______________________________________ • Researchers recently discovered an experimental vaccine that may help stop the buildup of these glue-like, 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 – __________________________________________ __________________________________________ __ • Central Nervous System – __________________________________________ __________________________________________ __ PERIPHERAL & CENTRAL NERVOUS SYSTEM (CONT.) • Nerves – String-like 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 __________________________________________ __________________________________________ __ – opposite charges __________ and like charges ___________ 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: 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 ___________________________, with the first occurring at the beginning of the axon 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 • ______________________________________ – inhibitory transmitters • ______________________________________ 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 ____________________, which means that it depresses the activity of the _________________________________________ WHAT DOES ALCOHOL DO? • Alcohol affects the brain by imitating a naturally occurring neurotransmitter, GABA • GABA Neurons – GABA neurons have ______________________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 _________________ __________________________________________________ WHAT DOES ALCOHOL DO? (CONT.) • many people drink alcohol to ______________________ ____________________________________________ • 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 – A__________________ – G___________________ – N____________________ – E_____________________ – D_____________________ – S______________________ NEW TRANSMITTERS (CONT.) • New – Endorphins (1970’s) • _______________________ • ____________ effects of pain during great bodily stress – Anandamide (1990’s) • similar to THC (active ingredient in marijuana) – involved with » memory » Motor movements » 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, _____________reaction to some stimulus – neural connections underlying a reflex are prewired by genetic instructions REFLEX (CONT.) • Reflex sequence – sensors • _______________________________________ – afferent neurons • carry information from ______________________ _________________________________________ _ 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 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 _______________________________ ____________________________________________ – L-dopa is a medication that _____________ 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 • Removing part of the brain – Thalamotomy (Michael J. Fox) • Brain Stimulation – ________________________________________ – ________________________________________ – ________________________________________