the biological basis of behavior

Chapter 2 - Biological Basis of Behavior

Psychology: An IntroductionCharles A. Morris & Albert A. Maisto 2005 Prentice Hall

The Biological Basis of Behavior
Chapter 2


Vocabulary Chapter 2
NeuronsDendritesSynapseNeurotransmittersReceptor siteCerebellumThalamusHypothalamusCerebral cortex
Occipital LobeTemporal LobeFrontal LobeCorpus CallosumSpinal cordAdrenal glandsGenes


Neurons: The Messengers
About 100 billion neurons (nerve cells) in the human brainNeurons have many of the same features as other cellsNucleusCytoplasmCell membraneWhat makes neurons unique is their shape and function


Structure of Neurons
DendritesCarry information to the cell body from other neuronsCell Body (Soma)Contains nucleusAxonCarries information to the next cellMyelin SheathInsulates the axon and speeds up the neural impulse


Types of Neurons
Sensory neuronsCarry information from sensory systems to the brainAlso referred to as afferentMotor neuronsCarry information from the brain to muscles and glandsAlso referred to as efferentInterneuronsCarry information between other neurons


Glial Cells
Cells that insulate and support neuronsCreate the myelin sheathRemove waste productsProvide nourishmentPrevent harmful substances from entering the brain


The Neural Impulse


The Neural Impulse
IonsCharged moleculesResting PotentialWhen more negative ions are inside the neuron than outsideCharge is approximately -70mVNeuron is not transmitting information


The Neural Impulse
PolarizationWhen the electrical charge of a cell moves away from zero

DepolarizationWhen the electrical charge of a cell moves toward zero


The Neural Impulse
Action PotentialSudden, massive change in charge in the neuronOccurs when depolarization reaches the threshold of excitationIons flow across cell membrane


The Neural Impulse
Graded PotentialsSubthreshold depolarizationMany subthreshold depolarizations are added together to produce an action potential (a process known as summation)


The Neural Impulse
All-or-None LawA neuron either fires or it does notWhen it does fire, it will always produce an impulse of the same strengthIntensity of a stimulus is coded by the frequency of action potentials


The Neural Impulse
Absolute refractory periodPeriod immediately after an action potential when another action potential cannot occurRelative refractory periodPeriod following absolute refractory period when a neuron will only respond to a stronger than normal impulse


The Synapse
Synaptic space (synaptic cleft)Tiny gap between neuronsTerminal button Enlarged area at the end of an axonThe synapseComposed of the terminal button of one neuron, the synaptic space, and the dendrites or cell body of the receiving neuron


Transmission Between Neurons
Synaptic vesiclesSacs in terminal button that release chemicals into synaptic spaceNeurotransmittersChemicals released by synaptic vesiclesReceptor sitesLocation on receptor neuron for specific neurotransmitter


Some Well-Known Neurotransmitters
Acetylcholine (ACh)Released at the neuromuscular junctionPlays an important role in arousal and attentionLoss of ACh producing cells is linked to Alzheimers DiseaseDopamineAffects neurons associated with voluntary movementPlays a role in learning, memory, and emotionsLoss of dopamine-producing cells causes symptoms of Parkinsons Disease


Some Well-Known Neurotransmitters
SerotoninFound throughout the brainAppears to sets an emotional toneLow serotonin levels are implicated in depressionEndorphinsReduce pain by inhibiting or turning down neurons that transmit pain information


Psychopharmacology
Most psychoactive drugs (and toxins) work by blocking or enhancing synaptic transmissionBotulismBlocks release of ACh at the neuromuscular junction, causing paralysisBotox is botulism toxin used to prevent facial muscles from making wrinkles


Psychopharmacology
CurareCan stun or kill prey quicklyBlocks ACh receptors causing paralysisAntipsychotic medicationsBlock dopamine receptorsReduces schizophrenic hallucinationsCaffeineIncreases the release of excitatory neurotransmitters by blocking the inhibitory neurotransmitter adenosine


Psychopharmacology
CocainePrevents reabsorption of dopamineLeads to heightened arousal of entire nervous system


Neural Plasticity
The brain can be changed, both structurally and chemically, by experienceRat studies show that an enriched environment leads to larger neurons with more connectionsHas also been shown in humansRecent research has uncovered evidence of neurogenesis, or the production of new brain cells, in human brains


Nervous System Organization
Central nervous system (CNS)Consists of the brain and spinal cordPeripheral nervous systemConnects the CNS to the rest of the bodySomatic nervous systemAutonomic nervous system


Central Nervous System


The Brain The Central Core
MedullaControls breathing, heart rate, and blood pressurePonsMaintains the sleep-wake cycleCerebellumCoordinates bodys movements


ThalamusRelays information from sensory receptors to the brainHypothalamus Influences motivated behaviorRegulates hunger, thirst, body temperature, and sexual drive.Directly involved in emotional behavior


Reticular formationNetwork of neurons found throughout the brainServes to alert and arouse higher brain in response to incoming information


The Brain The Limbic System
Ring of structures located between the central core and the cerebral hemispheresImportant to learning and emotional behaviorHippocampus essential in formation of new memoriesAmygdala, together with the hippocampus, is important for regulating emotions


The Cerebral Cortex
Occipital lobeReceives and processes visual information Temporal lobeComplex visual tasks such as face recognitionReceives and processed auditory informationInvolved in balance, some emotions and motivationsSome language processing


The Cerebral Cortex
Parietal lobeReceives sensory information from body Involved in spatial abilitiesFrontal lobeCoordinated information from other lobesControls voluntary movement, attention, setting goals, and expression of appropriate emotions


Hemispheric Specialization
Corpus CallosumFibers that connect the two hemispheresAllow close communication between left and right hemishphereEach hemisphere appears to specialize in certain functions


Split-Brain Research
Much information about functions of each hemisphere has come from studying split-brain patients


Tools for Studying the Nervous System


Microelectrode Techniques
Very small electrodes inserted into individual neuronsUsed to study activity of a single neuron


Macroelectrode Techniques
Used to get a picture of overall activity in the brainAn example is an EEG, which uses electrodes placed on a persons scalp to measure brain activity


Structural Imaging
Computerized Axial Tomography (CT-scan)Uses X-rays to create a 3-dimensional image of the brainMagnetic Resonance Imaging (MRI)Uses a magnetic field and radio waves to produce images


Functional Imaging
EEG imagingelectrical activity on the scalp from millions of neurons is used to produce a continuous picture of activity in the brainMagentoencephalography (MEG) and Magnetic source imaging (MSI)Can localize activity more precisely than EEG


Functional Imaging
Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT)Use radioactive glucose to determine location of greatest brain activityFunctional Magnetic Resonance Imaging (fMRI)Shows function and structure by measuring movement of blood molecules within the brain


The Spinal Cord


The Spinal Cord
Complex cable of nerves that connects brain to rest of the bodyCarries motor impulses from the brain to internal organs and musclesCarries sensory information from extremities and internal organs to the brain


The Spinal Cord
The spinal cord controls some protective reflex movements without any input from the brain


The Peripheral Nervous System


The Somatic Nervous System
Consists of neurons that communicate between the body and the brainAfferent neuronsNeurons that carry messages from sense organs to spinal cordEfferent neuronsNeurons that carry messages from the spinal cord or brain to muscles and glands


The Autonomic Nervous System
Sympathetic divisionMost active when you are angry, afraid, or arousedFight-or-flight responseIncreases heart rate and breathingStops digestion


The Autonomic Nervous System
Parasympathetic divisionCalms bodyProduces effects opposite to those of the sympathetic divisionReduces heart rate and breathingRestores digestion


The Endocrine System


Helps coordinate and integrate complex psychological reactionsEndocrine glands secrete hormones into the bloodstreamHormones serve to organize the nervous system and bodyHormones also activate behavior, such as sexual behavior


Thyroid glandSecretes hormones (primarily thyroxin) that control metabolismParathyroid glandsControl levels of calcium and phosphate which in turn controls levels of excitability


Pineal glandSecretes melatonin which regulates the sleep-wake cyclePancreasRegulates blood-sugar levelsSecretes insulin and glucagon


Pituitary glandReferred to as the master gland because it regulates many other glandsGonadsOvaries and testes secrete estrogens and androgensAdrenal glandsSecretes hormones in reaction to stress


Genes, Evolution, and Behavior


Genetics
Heredity - transmission of trait from one generation to nextChromosomesPairs of thread like bodies that contain genesDeoxyribonucleic acid (DNA)Organic molecule arranged in a double-helixContains the code of life


Behavior Genetics
Study of behavior from a genetic perspectiveAnimal behavior genetic studies include:Strain studiesSelection studies


Human Behavior Genetics
Family studiesAssume that close family members share more of a trait than non-relativesUsed to assess the heritability of psychological disorders or traitsTwin studiesUsed to determine how heritable a trait or disorder may beIdentical twins would have highest heritability


Human Behavior Genetics
Adoption studiesUsed to assess the influence of environmentMolecular geneticsDirect study of the genetic code


Evolutionary Psychology
Natural selectionSurvival of the fittestEvolutionary psychology looks at the adaptive or survival value of behaviors


Social Implications
Study of biological origins of behavior could lead to genocide and eugenics aimed at eliminating certain types of peopleCould also be used to create new categories of people, such as people bred to be good soldiers or manual laborers

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the biological basis of behavior

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