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 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)

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)

 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) 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  Pass these signals onto the cell body

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 signals generated in adjacent axons

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) –Exists between an end bulb and its adjacent body organ, heart, muscles, or cell body

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, muscles, and the body’s organs to and from the spinal cord –Those in the peripheral nervous system have the ability to grow or reattach if severed or damaged

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  ions are chemical particles that have electrical charges –Opposite charges attract and like charges repel

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 –Results in keeping axon charged by keeping sodium ions outside the axon membrane

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 end of the axon

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  block chemical locks and turn off neurons

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 –When GABA neurons are excited, they decrease neural activity

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 –Michael J. Fox

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)

 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)