Module 3Module 3

Brain’s Building Brain’s Building BlocksBlocks

ObjectivesObjectives

Students will be able to…Students will be able to…– Explain the causes and effects of Explain the causes and effects of

Alzheimer'sAlzheimer's– Distinguish the different parts of a Distinguish the different parts of a

neuron and discuss their roles.neuron and discuss their roles.

5 min quiz – Type 15 min quiz – Type 1

Please fill in the chart – DO NOT USE Please fill in the chart – DO NOT USE NOTES – you will be graded on NOTES – you will be graded on participation.participation.

Alzheimer’s diseaseAlzheimer’s disease

– 10% of cases start after age 5010% of cases start after age 50– 90% of cases start after age 6590% of cases start after age 65

Symptoms:Symptoms:– Problems with memoryProblems with memory– Forgetting and repeating thingsForgetting and repeating things– Getting lostGetting lost– Being mildly confusedBeing mildly confused

Alzheimer’s diseaseAlzheimer’s disease

– Period of 5 to 10 years, symptoms worsen Period of 5 to 10 years, symptoms worsen – Result is profound memory lossResult is profound memory loss– Lack of recognition of family and friendsLack of recognition of family and friends– Deterioration in personalityDeterioration in personality– Emotional outburstsEmotional outbursts– Widespread damage to the brain (hippocampus, Widespread damage to the brain (hippocampus,

involved in memory)involved in memory) no cure; always fatalno cure; always fatal

Alzheimer’s disease Alzheimer’s disease

Diagnosis and causesDiagnosis and causes– Researchers are close to identifying causeResearchers are close to identifying cause– GeneticGenetic– NeurologicalNeurological– Possible environmental factorsPossible environmental factors– Certain chemicals (proteins and peptides) that occur Certain chemicals (proteins and peptides) that occur

naturally in all brains seem to multiply and are believed naturally in all brains seem to multiply and are believed to cause Alzheimer’s (chemicals act like glue and to cause Alzheimer’s (chemicals act like glue and destroy brain cells)destroy brain cells)

– FilmFilm

DEVELOPMENT OF THE DEVELOPMENT OF THE BRAINBRAIN

GenesGenes– Chains of chemicals arranged like rungs on a Chains of chemicals arranged like rungs on a

twisting laddertwisting ladder– You have about 20,000 to 25,000 genes that You have about 20,000 to 25,000 genes that

contain chemical instructions equaling roughly contain chemical instructions equaling roughly 300,000 pages of written instructions300,000 pages of written instructions

– Genes program the development of individual Genes program the development of individual parts into a complex body and brainparts into a complex body and brain

DEVELOPMENT OF THE DEVELOPMENT OF THE BRAIN (CONT’D)BRAIN (CONT’D)

DEVELOPMENT OF THE DEVELOPMENT OF THE BRAIN (CONT’D)BRAIN (CONT’D)

STRUCTURE OF THE BRAINSTRUCTURE OF THE BRAIN

Human brainHuman brain

– Shaped like a small, wrinkled melonShaped like a small, wrinkled melon– 1,350 grams (less than three pounds)1,350 grams (less than three pounds)– Pinkish-white colorPinkish-white color– Consistency of firm Jell-OConsistency of firm Jell-O– Fueled by sugar (glucose)Fueled by sugar (glucose)– 1 trillion cells divided into1 trillion cells divided into

glial cellsglial cells neuronsneurons

STRUCTURE OF THE BRAIN STRUCTURE OF THE BRAIN (CONT’D)(CONT’D)

Glial cellsGlial cells

– Guide the growth of developing neuronsGuide the growth of developing neurons

– Wrap around neurons and form an insulation to Wrap around neurons and form an insulation to prevent interference from other electrical prevent interference from other electrical signalssignals

– Release chemicals that influence a neuron’s Release chemicals that influence a neuron’s growth and functiongrowth and function

STRUCTURE OF THE BRAIN STRUCTURE OF THE BRAIN (CONT’D)(CONT’D)

STRUCTURE OF THE BRAIN STRUCTURE OF THE BRAIN (CONT’D)(CONT’D)

Neuron Neuron

– Brain cell with two specialized extensionsBrain cell with two specialized extensions

– One extension is for receiving electrical signalsOne extension is for receiving electrical signals

– The other extension is for transmitting electrical signalsThe other extension is for transmitting electrical signals

STRUCTURE OF THE BRAIN (STRUCTURE OF THE BRAIN (CONT’D)CONT’D)

GROWTH OF NEW NEURONSGROWTH OF NEW NEURONS

Can a brain grow new neurons?Can a brain grow new neurons?– Canary brainCanary brain

can grow about 20,000 neurons a day during the can grow about 20,000 neurons a day during the spring (learns new breeding song)spring (learns new breeding song)

– Primate and human brainPrimate and human brain researchers conclude that adult monkey and human researchers conclude that adult monkey and human

brains are capable of growing relatively limited brains are capable of growing relatively limited numbers of neurons throughout adulthoodnumbers of neurons throughout adulthood

some new neurons play important role in continuing some new neurons play important role in continuing to learn and remember new things (hippocampus)to learn and remember new things (hippocampus)

GROWTH OF NEW NEURONS GROWTH OF NEW NEURONS (CONT’D)(CONT’D)

Repairing the brainRepairing the brain

– Advances in stem research suggest the human brain Advances in stem research suggest the human brain may be able to grow more neuronsmay be able to grow more neurons

– Repair damages due toRepair damages due to accidentaccident diseasedisease Alzheimer’sAlzheimer’s

BRAIN VERSUS MINDBRAIN VERSUS MIND

Mind-body question:Mind-body question:– How complex mental activities such as How complex mental activities such as

feelingfeelingthinkingthinking learninglearning

– can be explained by thecan be explained by thephysicalphysicalchemicalchemicalelectrical activitieselectrical activities

– of the brainof the brain

ALZHEIMER’S DISEASE AND ALZHEIMER’S DISEASE AND NEURONSNEURONS

Alzheimer’s diseaseAlzheimer’s disease

– Excessive buildup of glue-like substancesExcessive buildup of glue-like substances– Gradually destroy neuronsGradually destroy neurons

Researchers can study a person’s Researchers can study a person’s mental activities by taking brain scans mental activities by taking brain scans of the neural activities going on inside of the neural activities going on inside the living brainthe living brain

ALZHEIMER’S DISEASE AND ALZHEIMER’S DISEASE AND NEURONSNEURONS

NEURONNEURON

PARTS OF THE NEURONPARTS OF THE NEURON

Cell bodyCell body

– Large egg-shaped structure that provides fuel, Large egg-shaped structure that provides fuel, manufactures chemicals, and maintains the manufactures chemicals, and maintains the entire neuron in working orderentire neuron in working order

DendriteDendrite

– Branch-like extensions that arise from the cell Branch-like extensions that arise from the cell bodybodyReceive signals from other neurons, muscles, or Receive signals from other neurons, muscles, or

sense organssense organs

Pass these signals onto the cell bodyPass these signals onto the cell body

PARTS OF THE NEURON PARTS OF THE NEURON (CONT’D)(CONT’D)

AxonAxon– A single thread-like structure that A single thread-like structure that

extends/carries signals away from the cell body extends/carries signals away from the cell body to neighboring neurons, organs, or musclesto neighboring neurons, organs, or muscles

Myelin sheathMyelin sheath– Looks like separate tube-like segments Looks like separate tube-like segments

composed of fatty material that wraps around composed of fatty material that wraps around and insulates an axonand insulates an axon

– Prevents interference from electrical signals Prevents interference from electrical signals generated in adjacent axonsgenerated in adjacent axons

PARTS OF THE NEURON PARTS OF THE NEURON (CONT’D)(CONT’D)

End bulbs or terminal bulbsEnd bulbs or terminal bulbs– Located at extreme ends of the axon’s branchesLocated at extreme ends of the axon’s branches– Miniature container that stores chemicals called Miniature container that stores chemicals called

neurotransmitters (used to communicate with neurotransmitters (used to communicate with neighboring cells)neighboring cells)

SynapseSynapse– Infinitely small space (20-30 billionths of a Infinitely small space (20-30 billionths of a

meter)meter)– Exists between an end bulb and its adjacent Exists between an end bulb and its adjacent

body organ, heart, muscles, or cell bodybody organ, heart, muscles, or cell body

NERUONS VERSUS NERVESNERUONS VERSUS NERVES

Reattaching limbsReattaching limbs– John ThomasJohn Thomas

lost arms in farming accidentlost arms in farming accident

Transplanting a faceTransplanting a face– IsabelleIsabelle

face severely disfigured by a dogface severely disfigured by a dogreceivedreceived

– new nosenew nose– lipslips– chinchin

NERUONS VERSUS NERVESNERUONS VERSUS NERVES

PERIPHERAL & CENTRAL PERIPHERAL & CENTRAL NERVOUS SYSTEMNERVOUS SYSTEM

Peripheral nervous systemPeripheral nervous system– Made up of nerves located throughout the body, Made up of nerves located throughout the body,

except in the brain and spinal cordexcept in the brain and spinal cord

NervesNerves– String-like bundles of axons and dendrites that String-like bundles of axons and dendrites that

come from the spinal cord and are held together come from the spinal cord and are held together by connective tissueby connective tissue

– Carry information from the senses, skin, muscles, Carry information from the senses, skin, muscles, and the body’s organs to and from the spinal cordand the body’s organs to and from the spinal cord

– Those in the peripheral nervous system have the Those in the peripheral nervous system have the ability to grow or reattach if severed or damagedability to grow or reattach if severed or damaged

PERIPHERAL & CENTRAL PERIPHERAL & CENTRAL NERVOUS SYSTEM (CONT’D)NERVOUS SYSTEM (CONT’D)

Central nervous systemCentral nervous system– Made up of neurons located in the brain Made up of neurons located in the brain

and spinal cordand spinal cord

Multiple sclerosisMultiple sclerosis– Disease that attacks the myelin sheaths that Disease that attacks the myelin sheaths that

wrap around and insulate cells in the central wrap around and insulate cells in the central nervous systemnervous system

SENDING INFORMATION: SENDING INFORMATION: ACTION POTENTIAL ACTION POTENTIAL

SEQUENCESEQUENCE– Stimulus (tack or nail)Stimulus (tack or nail)– Skin has sensors that pick up mechanical Skin has sensors that pick up mechanical

pressure and transform it into electrical signalspressure and transform it into electrical signals– Signals are sent by the neuron’s axon to Signals are sent by the neuron’s axon to

various areas in the spinal cord and brainvarious areas in the spinal cord and brain– Brain interprets electrical signals as “pain”Brain interprets electrical signals as “pain”

axon membrane has chemical gates that can open axon membrane has chemical gates that can open to allow electrically charged particles to enter or to allow electrically charged particles to enter or can close to keep out these particlescan close to keep out these particles

ions are chemical particles that have electrical ions are chemical particles that have electrical chargescharges

– Opposite charges attract and like charges Opposite charges attract and like charges repelrepel

SENDING INFORMATION: SENDING INFORMATION: ACTION POTENTIAL ACTION POTENTIAL

SEQUENCE (CONT’D)SEQUENCE (CONT’D)

SENDING INFORMATION: SENDING INFORMATION: ACTION POTENTIAL ACTION POTENTIAL

SEQUENCE (CONT’D)SEQUENCE (CONT’D) Resting stateResting state– Axon has a chargeAxon has a charge– Charge results from the axon membrane Charge results from the axon membrane

separating positive ions on the outside from separating positive ions on the outside from negative ions on the insidenegative ions on the inside

Sodium pumpSodium pump– Transport process that picks up any sodium ions Transport process that picks up any sodium ions

that enter the axon’s chemical gates and that enter the axon’s chemical gates and returns them back outsidereturns them back outside

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

SENDING INFORMATION: SENDING INFORMATION: ACTION POTENTIAL ACTION POTENTIAL

SEQUENCE (CONT’D)SEQUENCE (CONT’D) Action potentialAction potential

– Tiny electric current generated when Tiny electric current generated when positive sodium ions rush inside the axonpositive sodium ions rush inside the axon

– Enormous increase of sodium ions inside the Enormous increase of sodium ions inside the axon causes the inside of the axon to axon causes the inside of the axon to reverse its chargereverse its charge

– Inside becomes positive and outside Inside becomes positive and outside becomes negativebecomes negative

SENDING INFORMATION: SENDING INFORMATION: NERVE IMPULSENERVE IMPULSE

SENDING INFORMATION: SENDING INFORMATION: NERVE IMPULSENERVE IMPULSE (CONT’D) (CONT’D)

Nerve impulseNerve impulse– Nerve impulse is made up of six action Nerve impulse is made up of six action

potentials, with the first occurring at the potentials, with the first occurring at the beginning of the axonbeginning of the axon

All-or-none lawAll-or-none law– If an action potential starts at the beginning If an action potential starts at the beginning

of the axon, the action potential will of the axon, the action potential will continue at the same speed segment to continue at the same speed segment to segment to the very end of the axonsegment to the very end of the axon

SENDING INFORMATION: SENDING INFORMATION: NERVE IMPULSENERVE IMPULSE (CONT’D) (CONT’D)

TRANSMITTERSTRANSMITTERS

A transmitter is a chemical messenger A transmitter is a chemical messenger that transmits information between that transmits information between nerves and body organs, such as muscles nerves and body organs, such as muscles and heartand heart

Excitatory and inhibitoryExcitatory and inhibitory– Excitatory transmittersExcitatory transmitters

open chemical locks and turn on neuronsopen chemical locks and turn on neurons

– Inhibitory transmittersInhibitory transmittersblock chemical locks and turn off neuronsblock chemical locks and turn off neurons

NEUROTRANSMITTERSNEUROTRANSMITTERS

NeurotransmittersNeurotransmitters

– Dozens of different chemicals made by Dozens of different chemicals made by neurons and then used for neurons and then used for communication between neurons during communication between neurons during the performance of mental or physical the performance of mental or physical activitiesactivities

NEUROTRANSMITTERS NEUROTRANSMITTERS (CONT’D)(CONT’D)

ALCOHOLALCOHOL

Alcohol (ethyl alcohol)Alcohol (ethyl alcohol)

– A psychoactive drug classified as a A psychoactive drug classified as a depressant, which means that it depressant, which means that it depresses the activity of the central depresses the activity of the central nervous systemnervous system

ALCOHOL (CONT’D)ALCOHOL (CONT’D)

WHAT DOES ALCOHOL DO?WHAT DOES ALCOHOL DO? Alcohol affects the brain by imitating a Alcohol affects the brain by imitating a

naturally occurring neurotransmitter, GABAnaturally occurring neurotransmitter, GABA GABA neuronsGABA neurons

– GABA neurons have chemical locks that can be GABA neurons have chemical locks that can be opened by chemical keys in the form of the opened by chemical keys in the form of the neurotransmitter GABAneurotransmitter GABA

GABA keysGABA keys– Alcohol molecules so closely resemble those of Alcohol molecules so closely resemble those of

the GABA neurotransmitter that alcohol can the GABA neurotransmitter that alcohol can function like GABA keys and open GABA receptorsfunction like GABA keys and open GABA receptors

– When GABA neurons are excited, they decrease When GABA neurons are excited, they decrease neural activityneural activity

WHAT DOES ALCOHOL DO? WHAT DOES ALCOHOL DO? (CONT’D)(CONT’D)

Many people drink alcohol to feel less Many people drink alcohol to feel less anxious and more relaxedanxious and more relaxed

Appears to be a biological link Appears to be a biological link between alcohol and anxietybetween alcohol and anxiety

Deficiency in a specific brain protein is Deficiency in a specific brain protein is associated with high anxiety and associated with high anxiety and excessive alcohol useexcessive alcohol use

NEW TRANSMITTERSNEW TRANSMITTERS

Number of well-known Number of well-known neurotransmitters, such asneurotransmitters, such as

– NorepinephrineNorepinephrine– GABAGABA– DopamineDopamine– SerotoninSerotonin

NEW TRANSMITTERS NEW TRANSMITTERS (CONT’D)(CONT’D)

– Endorphins (1970s)Endorphins (1970s)painkiller similar to morphinepainkiller similar to morphinedecreases effects of pain during great bodily decreases effects of pain during great bodily

stressstress

– Anandamide (1990s)Anandamide (1990s)similar to THC (active ingredient in similar to THC (active ingredient in

marijuana)marijuana)– involved withinvolved with

memorymemory motor coordinationmotor coordination emotionsemotions

NEW TRANSMITTERS NEW TRANSMITTERS (CONT’D)(CONT’D)

Anandamide may help people Anandamide may help people regulate emotions, which would help regulate emotions, which would help them to better deal with anxiety and them to better deal with anxiety and stressstress

– Nitric oxide (mid-1990s)Nitric oxide (mid-1990s)may be involved in regulating aggressive may be involved in regulating aggressive

and impulsive behaviorsand impulsive behaviors

NEW TRANSMITTERS NEW TRANSMITTERS (CONT’D)(CONT’D)

– Orexin (hypocretin)Orexin (hypocretin)

late 1990slate 1990s involved in the brain’s pleasure and reward involved in the brain’s pleasure and reward

systemsystemhigh levels: cravings for food or drugshigh levels: cravings for food or drugs low levels: reduce cravingslow levels: reduce cravings involved in sleep and wakefulnessinvolved in sleep and wakefulness

– low levels have been linked to narcolepsylow levels have been linked to narcolepsy

REFLEXREFLEX

ReflexReflex

– Unlearned, involuntary reaction to some Unlearned, involuntary reaction to some stimulusstimulus

– Neural connections underlying a reflex Neural connections underlying a reflex are prewired by genetic instructionsare prewired by genetic instructions

REFLEX (CONT’D)REFLEX (CONT’D)

Reflex sequenceReflex sequence

– SensorsSensorssensors trigger neurons that start the sensors trigger neurons that start the

withdrawal effectwithdrawal effect

– Afferent neurons (sensory neurons)Afferent neurons (sensory neurons)carry information from the senses to the carry information from the senses to the

spinal cordspinal cord

REFLEX (CONT’D)REFLEX (CONT’D)

– InterneuronInterneuronrelatively short neuron whose primary task relatively short neuron whose primary task

is making connections between other is making connections between other neuronsneurons

– Efferent neuronEfferent neuroncarries information away from the spinal carries information away from the spinal

cord to produce responses in various cord to produce responses in various muscles and organs throughout the bodymuscles and organs throughout the body

REFLEX (CONT’D)REFLEX (CONT’D)

PARKINSON’S DISEASEPARKINSON’S DISEASE

Parkinson’s diseaseParkinson’s disease

– Includes symptoms of tremors and shakes in Includes symptoms of tremors and shakes in the limbs, a slowing of voluntary movements, the limbs, a slowing of voluntary movements, muscle stiffness, problems with balance and muscle stiffness, problems with balance and coordination, and feelings of depressioncoordination, and feelings of depression

– As the disease progresses, patients develop a As the disease progresses, patients develop a shuffling walk and may suddenly freeze in shuffling walk and may suddenly freeze in space for minutes or hours at a timespace for minutes or hours at a time

– Michael J. FoxMichael J. Fox

PARKINSON’S DISEASE PARKINSON’S DISEASE (CONT’D)(CONT’D)

Parkinson’s diseaseParkinson’s disease

– Caused by destruction of neurons that Caused by destruction of neurons that produce dopamineproduce dopamine

– L-dopa is a medication that boosts the L-dopa is a medication that boosts the levels of dopamine in the brain levels of dopamine in the brain

– Eventually, the drug causes involuntary Eventually, the drug causes involuntary jerky movements jerky movements

– After prolonged use, L-dopa’s beneficial After prolonged use, L-dopa’s beneficial effect may be replaced by unwanted jerky effect may be replaced by unwanted jerky movementsmovements

EXPERIMENTAL EXPERIMENTAL TREATMENTSTREATMENTS

Sterotaxic procedureSterotaxic procedure

– Fixing a patient’s head in a holder and Fixing a patient’s head in a holder and drilling a small hole through the skulldrilling a small hole through the skull

– The holder has a syringe that can be The holder has a syringe that can be precisely guided into a predetermined precisely guided into a predetermined location in the brainlocation in the brain

EXPERIMENTAL EXPERIMENTAL TREATMENTS (CONT’D)TREATMENTS (CONT’D)

EXPERIMENTAL EXPERIMENTAL TREATMENTS (CONT’D)TREATMENTS (CONT’D)

EXPERIMENTAL EXPERIMENTAL TREATMENTS (CONT’D)TREATMENTS (CONT’D)

Removing part of the brainRemoving part of the brain– Thalamotomy (Michael J. Fox)Thalamotomy (Michael J. Fox)

Brain stimulationBrain stimulation– Electrodes placed into thalamusElectrodes placed into thalamus– Patient controls amount of stimulusPatient controls amount of stimulus– Helps reduce tremorsHelps reduce tremors

EXPERIMENTAL EXPERIMENTAL TREATMENTS (CONT’D)TREATMENTS (CONT’D)