4 Neuroscience and Behavior Chpt 2

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    Neuroscience andBehavior

    Chapter 2

    57-97

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    Introduction to Neuroscience

    Everything psychological is

    physiological.

    In the early 1800s

    phrenologywas the

    beginning of neuroscience.Phrenology was the idea

    that you could tell about a

    persons personality or

    mental skills from the shape

    of their head.

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    Biological Psychologists

    Scientists who study the relationship

    between biological activity and

    behavior call themselves many things,

    behavioral neuroscientists,physiological psychologists, or

    biopsychologists.

    Humans have the highest brain to

    body weight ratio of any animal. Mostof that is due to our large cerebral

    cortex or cerebrum.

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    Neural Communication (p58-

    65)

    Neurons are

    the most basicbuilding blockof allpsychologyand thenervous

    system. Neurons are a

    specializedcell. Cells arethe building

    blocks of allliving things,the smallestunit of life thatcan exist.

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    Neurons Each Neuron has a cell body, from which branches ofdendrites

    receive messages from other neurons. Then the large axon fibertransmits the message to other neurons or muscles or glands.Axons can actually be several feet long. A myelin sheath coversthe axon and helps speed along the messages, finally themessage is released from terminal branches at the end of theaxon.

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    5 Special Proteins In addition to normal cell activities neurons

    make some special types of proteins thathelp them in their job.

    Ion pumps (provide active transport of

    certain ions in the cell membrane) Ion channels (passive transport) Messenger proteins (neurotransmitter) Receptor proteins (are used to receive

    chemical signals) Enzymes (proteins) that degrade

    neurotransmitters

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    Types of Neurons

    Sensory neurons Input: vision, audition,

    smell, taste, touch, balance, proprioception

    Interneurons most numerous, make up

    most of the brain and allow internal

    communication within the nervous system.

    Motor neurons Output: movement,

    behavior

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    The Action Potential

    Neurons are connected

    not to just one other

    neuron but to hundreds

    or even thousands ofother neurons.

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    Action Potential Every millisecond a neuron will be receiving messages

    from these other neurons. Neurons receive only one of

    two messages:- EPSP (excitatorypost synaptic potential)

    FIRE!

    - IPSP (inhibitorypost-synaptic potential)

    Dont Fire! The neuron will calculate all the messages it gets, if it

    gets more excitatory messages than inhibitorymessages it will reach its threshold and fire the actionpotential.

    The action potential goes down the axon away from thecell body only.

    Action potentials are an all or nothingaction, there areno partial action potentials.

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    Action Potential

    The action potential is an electrical chargecreated by chemical reactions

    This is done by electrically charged atoms

    called ions. The interior of an axon has an excess of

    negatively charged ions making it negative. The outside of an axon has an excess of

    positively charged ions making it positive. This normal state is called the resting

    potential

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    Action Potential When an neuron receives enough

    EPSPs it changes the polarity ofthe selectively permeable axon

    membrane closest to the cell body

    and allows positive sodium ions to

    rush in.

    This depolarizes the next part ofthe axon and so on.

    After the reaction the axon goes

    back to normal in a short amount

    of time called the refractoryperiod.

    This process can repeat 100 or

    even 1000 times a second.

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    Active and passive ionmovement Ions are moved

    in and out of theselectivelypermeablemembrane by ion

    pumps andchannels in thecell membrane

    http://www.brooks

    Ion pump uses energyIon channel

    doesnt need energy

    Ions are movedin and out of theselectivelypermeablemembrane by ion

    pumps andchannels in thecell membrane

    http://www.brooks

    http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.htmlhttp://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.htmlhttp://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.htmlhttp://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.html
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    The Synapse andNeurotransmitters Action Potentials cause the release ofneurotransmitters from axon terminals into thesynapse, or a tiny space between where one neuronends and another begins.

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    Neurotransmitter release Within 1/10,000th of a second neurotransmitters cross

    the synaptic gap and bind to receptor cells on theother neuron, like the action potential this lets ionsenter the receiving neuron making either EPSPs orIPSPs

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    Reuptake Reuptake is a process

    by whichneurotransmitters are

    reabsorbed by the

    neurons who sent them.

    This is importantbecause if it did not

    happen the

    neurotransmitters would

    continue to triggerEPSPs as long as they

    were in the synapse.

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    Neurotransmitters -continued

    Undersupply linked toseizures, tremors and

    insomnia

    Major inhibitoryneurotransmitterGABA (gamma-

    aminobutyric

    acid)

    Endorphins - are naturally occurring neurotransmitters that act as opiates.

    They are released usually in times of great pain or vigorous exercise.

    Because of the body has receptors for these transmitters this is why

    opiates (morphine, vicodin, oxy-contin, heroin, etc.) are so effective at

    producing a pleasurable, pain relieving feeling in humans. Becauseendorphins are not normally occurring in great quantities its very easy to

    flood the body with them but then its very hard to replace them naturally

    this is why opiates are so addictive.

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    How Drugs and other Chemicalsaffect Neurotransmission

    Drugs affectneurotransmission inone of three ways:

    Agonists exciteareshaped enough just like

    a regularneurotransmitter totrigger the same effect.

    Antagonists inhibitmay be shaped enoughlike a neurotransmitter

    to rest on a receptor siteblocking othertransmitters but it itselfdoes not trigger aresponse at the site.

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    The Nervous System

    The Nervous System

    PeripheralCentral

    (brain and spinal cord)

    Autonomic(controls self regulated

    Actions of internal organs

    And glands)

    Somatic(controls voluntary movements

    Of skeletal muscles)

    Sympathetic (arousing)

    Parasympathetic (calming)

    The three types of neurons, sensory, interneurons, and motor neurons

    make up the Nervous System which is categorized into these majordivisions:

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    The Peripheral NervousSystem As the chart indicates the peripheral nervous

    system is made of 2 parts the autonomic and

    somatic systems.

    The somatic nerves control your voluntarymuscles, your movement.

    The automatic system controls all the rest of

    the things your body does constantly to keepyou alive that you dont think about, like

    beating your heart.

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    The Autonomic Nervous

    System controls the glands and

    internal organs.

    The Sympathetic system isresponsible for the arousalof this

    system for defensive action.

    The Parasympathetic system is

    responsible forcalmingthis

    system, together they work to

    regulate your bodys internal

    functions to your everyday needs.

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    Central Nervous System:Spinal Cord The spinal cord is an information highway

    connecting the brain and the peripheral

    nervous system.

    The spinal cord is responsible for variousreflexes from sensation and pain such as

    yanking your hand away from a flame. These

    reflexes are usually caused by an interneuronconnecting the sensory and motor neurons

    from a particular area.

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    Diagram of a reflex a sensory and motor neuron connectedby an interneuron in the spinal cord

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    Reflexes

    While reflexes could happen in a headless

    warm body any interpretation of sensation or

    voluntary movement originates in the brain.

    Therefore, people who have had their spinalcord damaged or cut often cannot feel or

    move below that portion of their body, but

    they could have reflexive reactions.

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    Neural NetworksA grain of sand size speck of your brain contains 100,000 neurons with a billion

    talking synapses. Neurons form connections with other neurons nearby them tomake work groups that can carry out specific tasks, like learning the piano.

    Practice, repetition of using certain neuro-pathways strengthens them, and makes

    you better at that task.

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    The Brain (tools of discovery)

    Lesion method destroying a part of an

    animals brain and recording the results in

    behavior.

    Clinical Observation observing someonewho has had brain damage.

    Manipulation stimulating part of the brain

    and using modern instruments to record theresults, such as an EEG.

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    The Brain (tools of discovery)

    Electroencephalogram(EEG) records the overallelectrical activity of neuronsin the brain by recording thewaves of energy that

    appear. Like studying a carby listening to the engine not very precise.

    Computed tomography(CT or CAT scan) using a

    series of x-rays a computermakes a map of your braininternally used to seebrain damage.

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    The Brain (tools of discovery) Positron Emission Topography

    (PET scan) by injecting users

    with radioactive glucose (food)this machine sees which areas ofthe brain are most active duringcertain stimuli by measuring howmuch food is being used byactive neurons. Great for tellingus what different parts of thebrain do.

    Magnetic Resonance Imaging(MRI) The MRI puts the brain ina strong magnetic field and thendistorts very briefly atoms with apulse of radio waves, by

    recording the movement of atomsyou can create a computerizedpicture of the brain and of bloodflow (active areas) into the brain.

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    The Brain: The Brainstem

    The brainstem is the oldest part of the brain and

    is well developed in animals as well as humans.

    The bottom of the brainstem is called the medulla

    it controls your breathing and heart rate The reticular formation helps organize

    sensation nerves to go different parts of the brain

    as well as affects arousal.

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    The Limbic System

    A system of neural

    structures right above

    the brain stem that

    influence emotions

    such as fear and

    aggression and basic

    drives like hunger and

    sex. Includes the

    hypothalamus

    hippocampus, and

    amygdala.

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    Limbic System

    Amygdala primarily influences aggressionand fear

    Hypothalamus directs several

    maintenance activies like eating, drinking,body temp., has links to emotion andinfluences the endocrine system via thepituitary gland. Around this organ on many

    animals is a distinct reward center that canbe stimulated to make the animals feelpleasure.

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    Cerebral Cortex

    The cerebral cortex is what people usuallythink of as the brain. Its the wrinkled top ofthe Brain. The reason for the folds is that it

    increases surface area and allows for moreneurons. Glial Cells take care of neurons, they help

    guide their connections, give them nutrients,

    help cover axons with myelin sheaths, andthey can clean up ions and excessneurotransmitters

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    Functions of the Cortex

    While we may separate regions of the brain

    to help us study it we always have to keep in

    mind that the brain is a very complex organ.

    There is hardly ever just one region of thebrain that is being used for a particular task,

    usually several areas at once are being used

    for even the most simple things, like typing.

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    Motor Cortex

    At the back

    of the frontal

    lobe is the

    motor cortex

    which is in

    charge of

    muscle

    movement

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    SensoryCortex

    Right behind

    the Motor

    Cortex is the

    SensoryCortex where

    your touch

    sensations

    areprocessed.

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    Plasticity

    The brain has the amazing ability to reorganize

    itself.

    If brain damage occurs, neurons do not grow back,

    however neurons can change their function to allowthe brain to repair itself.

    Thus if your middle finger were cut off, the fingers

    next to it would become more sensitive because that

    part of your brain that used to process sensationfrom the middle finger will now be used to process

    more sensation from the other fingers nearby.

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    The Divided Brain

    Your brain is divided into two hemispheres.

    The left side of your brain controls the right

    side of your body and vice versa. The left

    side of your brain includes most speechareas while the right includes a lot of visual

    areas.

    Each side talks to the other side via theCorpus Callosum so they can work

    together.

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    Hemisphere Specializations

    Perceptual tasks are performed more in theright side of the brain (recognizing faces,pictures, art, subtle interpretation)

    Speaking or calculating are preformed morein the left side of the brain. (recognizingwords,

    Handedness is probably genetic, 95% of all

    humans are right-handed. Left handedpeople on average live 3 years shorter forunknown reasons

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    The Endocrine System

    The Endocrine system is a system ofcommunication via chemicals called

    hormones that it releases into the bloodstream. Hormones are chemical messengers mostly

    manufactured by the endocrine glands that

    affect other parts of the body. Manyhormones act just like neurotransmitters butare slower and have longer lasting effects.

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    Adrenal Glands Secrete

    epinephrine (adrenaline) and

    norepinephrine which arouse

    the body in times of stress

    Pituitary Gland the master

    gland under the influence of

    the hypothalamus it regulates

    growth and controls other

    endocrine glands.Thyroid affects metabolism

    Parathyroid affects calcium

    levels

    Pancreas regulates blood

    sugar levels

    Ovary secrets estrogen

    (female sex hormone)

    Testis secrets testosterone

    (male sex hormone)

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    Remember:

    Everything psychologicalis physiological!