Module 3

Brain’s Building Blocks

INTRODUCTION

• 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

INTRODUCTION (CONT’D)

• 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

INTRODUCTION (CONT’D)

• Alzheimer’s disease

• Diagnosis and causes– _____________________________________________– _____________________________________________– _____________________________________________– _____________________________________________– Certain chemicals (__________________) that occur

naturally in all brains seem to multiply and are believed to cause Alzheimer’s (________________________________)

DEVELOPMENT OF THE BRAIN

• Fact that your brain doesn’t develop into a nose is because of instructions contained in your genes

• 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

• ___________________• ___________________

STRUCTURE OF THE BRAIN (CONT’D)

• Glial cells

– _______________________________________

– ______________________________________________________________________________________________________________________________

– ______________________________________________________________________________________________________________________________

STRUCTURE OF THE BRAIN (CONT’D)

STRUCTURE OF THE BRAIN (CONT’D)

• Neuron

– ________________________________________

– ________________________________________

– ________________________________________________________________________________________________________________________________________________________________________

Neuron

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

PARTS OF THE NEURON• Cell body

– Large egg-shaped structure that provides ______________________________________________________________________________________________________________________________

• Dendrite– Branch-like extensions that arise from 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– ________________________________________________

______________________________________________________________________________

PARTS OF THE NEURON (CONT’D)

• End bulbs or terminal bulbs– Located at extreme ends of the axon’s branches– Miniature container that

______________________________________________________________________________________________________________________________

• 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

NEURONS 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,

________________________________________________________________________________________________

• Nerves– ___________________________________ that come from

the spinal cord and are held together by connective tissue

– Carry information from the ________________________________________________________________________________________________

– 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

____________________________________________________________________________________

• Multiple sclerosis– ________________________________________

________________________________________________________________________________________________________________________________________________________________

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)

SENDING INFORMATION: ACTION POTENTIAL SEQUENCE (CONT’D)

• Resting state– Axon has a charge– Charge results from the axon membrane separating

______________________________________________________________________________________________________________________________

• 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

– ______________________________________________________________________________________________________________________________

– Enormous __________ of sodium ions inside the axon causes the _______________to ___________ its charge

– Inside becomes ____________ and outside becomes __________________

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

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 (agonists)

• ________________________________________– Inhibitory transmitters (antagonists)

• ________________________________________

Agonists

Antagonists

NEUROTRANSMITTERS

• Neurotransmitters

– Dozens of different chemicals made by ____________________________ and then used for ________________ between neurons during the performance of _____________________________________________________________________________ activities

NEUROTRANSMITTERS (CONT’D)

Acetylcholine (ACH)

• Deals with motor movement and memory.

• Too much and you will….

• Too little and you will…

• Lack of ACH has been linked to Alzheimer’s disease.

Dopamine

• Deals with motor movement and alertness.

• Lack of dopamine has been linked to Parkinson’s disease.

• Too much has been linked to schizophrenia.

Serotonin

• Involved in mood control.

• Lack of serotonin has been linked to clinical depression.

ALCOHOL

• Alcohol (ethyl alcohol)

– A ____________________________________, which means that it _____________________ the activity of the ____________________________________________________________________________________

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

Neurotransmitters

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: ____________________________• low levels: ______________________________• involved in sleep and wakefulness

– _____________________________________

REFLEX

• Reflex

– ______________________________________________________________________________________________________________________________

– ________________________________________________________________________________________________________________________________________________________________________

REFLEX (CONT’D)

• Reflex sequence

– Sensors• ________________________________________

________________________________________________________________________________

– Afferent neurons (sensory neurons)• ________________________________________

________________________________________________________________________________

REFLEX (CONT’D)

– Interneuron• relatively short neuron whose primary task is

________________________________________________________________________________________________________________________

– Efferent neuron• ________________________________to produce

____________________ 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)

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)