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Module 3 Brain’s Building Blocks Objectives Students will be able to… – Explain the causes and effects of Alzheimer's – Distinguish the different parts of a neuron and discuss their roles. 5 min quiz – Type 1 Please fill in the chart – DO NOT USE NOTES – you will be graded on participation. Alzheimer’s disease – 10% of cases start after age 50 – 90% of cases start after age 65 Symptoms: – Problems with memory – Forgetting and repeating things – Getting lost – Being mildly confused Alzheimer’s disease – – – – – – Period of 5 to 10 years, symptoms worsen Result is profound memory loss Lack of recognition of family and friends Deterioration in personality Emotional outbursts Widespread damage to the brain (hippocampus, involved in memory) no cure; always fatal Alzheimer’s disease Diagnosis and causes – Researchers are close to identifying cause – Genetic – Neurological – Possible environmental factors – Certain chemicals (proteins and peptides) that occur naturally in all brains seem to multiply and are believed to cause Alzheimer’s (chemicals act like glue and destroy brain cells) – Film DEVELOPMENT OF THE BRAIN Genes – Chains of chemicals arranged like rungs on a twisting ladder – You have about 20,000 to 25,000 genes that contain chemical instructions equaling roughly 300,000 pages of written instructions – Genes program the development of individual parts into a complex body and brain DEVELOPMENT OF THE BRAIN (CONT’D) DEVELOPMENT OF THE BRAIN (CONT’D) STRUCTURE OF THE BRAIN Human – – – – – – brain Shaped like a small, wrinkled melon 1,350 grams (less than three 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’D) Glial cells – 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’D) STRUCTURE OF THE BRAIN (CONT’D) Neuron – Brain cell with two specialized extensions – One extension is for receiving electrical signals – The other extension is for transmitting electrical signals STRUCTURE OF THE BRAIN (CONT’D) 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’D) Repairing the brain – Advances in stem research suggest the human brain may be able to grow more neurons – Repair damages due to 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 ALZHEIMER’S DISEASE AND NEURONS Alzheimer’s disease – Excessive buildup of glue-like substances – Gradually destroy neurons Researchers can study a person’s mental activities by taking brain scans of the neural activities going on inside the living brain ALZHEIMER’S DISEASE AND NEURONS NEURON PARTS OF THE NEURON Cell body – Large egg-shaped structure that provides fuel, manufactures chemicals, and maintains the entire neuron in working order Dendrite – Branch-like extensions that arise from the cell body Receive signals from other neurons, muscles, or sense organs PARTS OF THE NEURON (CONT’D) Axon – A single thread-like structure that extends/carries signals away from the cell body to neighboring neurons, organs, or muscles Myelin sheath – Looks like separate tube-like segments composed of fatty material that wraps around and insulates an axon – Prevents interference from electrical PARTS OF THE NEURON (CONT’D) 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) 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 NERUONS VERSUS NERVES PERIPHERAL & CENTRAL NERVOUS SYSTEM Peripheral nervous system – Made up of nerves located throughout the body, except in the brain and spinal cord 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, PERIPHERAL & CENTRAL NERVOUS SYSTEM (CONT’D) Central nervous system – Made up of neurons located in the brain and spinal cord Multiple – sclerosis Disease that attacks the myelin sheaths that wrap around and insulate cells in the central nervous system SENDING INFORMATION: ACTION POTENTIAL SEQUENCE – Stimulus (tack or nail) – Skin has sensors that pick up mechanical pressure and transform it into electrical signals – Signals are sent by the neuron’s axon to various areas in the spinal cord and brain – Brain interprets electrical signals as “pain” axon membrane has chemical gates that can open to allow electrically charged particles to enter or can close to keep out these particles SENDING INFORMATION: ACTION POTENTIAL SEQUENCE (CONT’D) SENDING INFORMATION: ACTION POTENTIAL SEQUENCE (CONT’D) Resting state – Axon has a charge – Charge results from the axon membrane separating positive ions on the outside from negative ions on the inside Sodium pump – Transport process that picks up any sodium ions that enter the axon’s chemical gates and returns them back outside SENDING INFORMATION: ACTION POTENTIAL SEQUENCE (CONT’D) Action potential – Tiny electric current generated when 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: NERVE IMPULSE (CONT’D) Nerve impulse – Nerve impulse is made up of six action potentials, with the first occurring at the beginning of the axon 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 SENDING INFORMATION: NERVE IMPULSE (CONT’D) 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 NEUROTRANSMITTERS Neurotransmitters – Dozens of different chemicals made by neurons and then used for communication between neurons during the performance of mental or physical activities NEUROTRANSMITTERS (CONT’D) ALCOHOL Alcohol (ethyl alcohol) – A psychoactive drug classified as a depressant, which means that it depresses the activity of the central nervous system ALCOHOL (CONT’D) 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 WHAT DOES ALCOHOL DO? (CONT’D) 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 – Norepinephrine – GABA – Dopamine – Serotonin NEW TRANSMITTERS (CONT’D) – Endorphins (1970s) painkiller similar to morphine decreases effects of pain during great bodily stress – Anandamide (1990s) similar to THC (active ingredient in marijuana) – involved with memory motor coordination emotions NEW TRANSMITTERS (CONT’D) Anandamide may help people regulate emotions, which would help them to better deal with anxiety and stress – Nitric oxide (mid-1990s) may be involved in regulating aggressive and impulsive behaviors NEW TRANSMITTERS (CONT’D) – Orexin (hypocretin) late 1990s involved in the brain’s pleasure and reward system high levels: cravings for food or drugs low levels: reduce cravings involved in sleep and wakefulness – low levels have been linked to narcolepsy REFLEX Reflex – Unlearned, involuntary reaction to some stimulus – Neural connections underlying a reflex are prewired by genetic instructions REFLEX (CONT’D) Reflex sequence – Sensors sensors trigger neurons that start the withdrawal effect – Afferent neurons (sensory neurons) carry information from the senses to the spinal cord REFLEX (CONT’D) – Interneuron relatively short neuron whose primary task is making connections between other neurons – Efferent neuron carries information away from the spinal cord to produce responses in various muscles and organs throughout the body REFLEX (CONT’D) 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 PARKINSON’S DISEASE (CONT’D) Parkinson’s disease – 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 (CONT’D) EXPERIMENTAL TREATMENTS (CONT’D) EXPERIMENTAL TREATMENTS (CONT’D) 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 (CONT’D)