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Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Biological Basis of Behavior
Chapter 2
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Neurons: The MessengersAbout 100 billion neurons (nerve cells) in
the human brainNeurons have many of the same features
as other cellsNucleusCytoplasmCell membrane
What makes neurons unique is their shape and function
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Structure of Neurons Dendrites
Carry information to the cell body from other neurons
Cell Body (Soma) Contains nucleus
Axon Carries information to the
next cell Myelin Sheath
Insulates the axon and speeds up the neural impulse
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Types of Neurons Sensory neurons
Carry information from sensory systems to the brain Also referred to as afferent
Motor neurons Carry information from the brain to muscles and
glands Also referred to as efferent
Interneurons Carry information between other neurons
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Glial CellsCells that insulate and support neuronsCreate the myelin sheathRemove waste productsProvide nourishmentPrevent harmful substances from entering
the brain
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Neural Impulse
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Neural Impulse Ions
Charged molecules Resting Potential
When more negative ions are inside the neuron than outside
Charge is approximately -70mV
Neuron is not transmitting information
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Neural ImpulsePolarization
When the electrical charge of a cell moves away from zero
DepolarizationWhen the electrical charge of a cell moves
toward zero
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Neural Impulse Action Potential
Sudden, massive change in charge in the neuron
Occurs when depolarization reaches the threshold of excitation
Ions flow across cell membrane
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Neural ImpulseGraded Potentials
Subthreshold depolarizationMany subthreshold depolarizations are added
together to produce an action potential (a process known as summation)
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Neural ImpulseAll-or-None Law
A 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
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Neural Impulse Absolute refractory period
Period immediately after an action potential when another action potential cannot occur
Relative refractory period Period following absolute
refractory period when a neuron will only respond to a stronger than normal impulse
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The SynapseSynaptic space (synaptic cleft)
Tiny gap between neuronsTerminal button
Enlarged area at the end of an axonThe synapse
Composed of the terminal button of one neuron, the synaptic space, and the dendrites or cell body of the receiving neuron
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Transmission Between Neurons Synaptic vesicles
Sacs in terminal button that release chemicals into synaptic space
Neurotransmitters Chemicals released by
synaptic vesicles Receptor sites
Location on receptor neuron for specific neurotransmitter
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Some Well-Known Neurotransmitters
Acetylcholine (ACh) Released at the neuromuscular junction Plays an important role in arousal and attention Loss of ACh producing cells is linked to Alzheimer’s
Disease Dopamine
Affects neurons associated with voluntary movement Plays a role in learning, memory, and emotions Loss of dopamine-producing cells causes symptoms
of Parkinson’s Disease
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Some Well-Known Neurotransmitters
SerotoninFound throughout the brainAppears to sets an “emotional tone”Low serotonin levels are implicated in
depressionEndorphins
Reduce pain by inhibiting or “turning down” neurons that transmit pain information
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
PsychopharmacologyMost psychoactive drugs (and toxins) work
by blocking or enhancing synaptic transmission
BotulismBlocks release of ACh at the neuromuscular
junction, causing paralysis“Botox” is botulism toxin used to prevent facial
muscles from making wrinkles
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Psychopharmacology Curare
Can stun or kill prey quickly Blocks ACh receptors causing paralysis
Antipsychotic medications Block dopamine receptors Reduces schizophrenic hallucinations
Caffeine Increases the release of excitatory neurotransmitters
by blocking the inhibitory neurotransmitter adenosine
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
PsychopharmacologyCocaine
Prevents reabsorption of dopamineLeads to heightened arousal of entire nervous
system
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Neural PlasticityThe brain can be changed, both structurally
and chemically, by experienceRat studies show that an “enriched”
environment leads to larger neurons with more connections
Has also been shown in humansRecent research has uncovered evidence of
neurogenesis, or the production of new brain cells, in human brains
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Nervous System Organization Central nervous
system (CNS) Consists of the brain
and spinal cord Peripheral nervous
system Connects the CNS to
the rest of the body Somatic nervous
system Autonomic nervous
system
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Central Nervous System
Central Nervous System
Brain Spinal Cord
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Brain – The Central Core Medulla
Controls breathing, heart rate, and blood pressure
Pons Maintains the sleep-
wake cycle Cerebellum
Coordinates body’s movements
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Brain – The Central Core Thalamus
Relays information from sensory receptors to the brain
Hypothalamus Influences motivated
behavior Regulates hunger, thirst,
body temperature, and sexual drive.
Directly involved in emotional behavior
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Brain – The Central CoreReticular formation
Network of neurons found throughout the brain
Serves to alert and arouse higher brain in response to incoming information
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Brain – The Limbic System Ring of structures located
between the central core and the cerebral hemispheres
Important to learning and emotional behavior Hippocampus essential in
formation of new memories Amygdala, together with
the hippocampus, is important for regulating emotions
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Cerebral Cortex Occipital lobe
Receives and processes visual information
Temporal lobe Complex visual tasks such
as face recognition Receives and processed
auditory information Involved in balance, some
emotions and motivations Some language processing
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Cerebral Cortex Parietal lobe
Receives sensory information from body
Involved in spatial abilities Frontal lobe
Coordinated information from other lobes
Controls voluntary movement, attention, setting goals, and expression of appropriate emotions
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Hemispheric Specialization Corpus Callosum
Fibers that connect the two hemispheres
Allow close communication between left and right hemishphere
Each hemisphere appears to specialize in certain functions
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Split-Brain ResearchMuch information about functions of each
hemisphere has come from studying split-brain patients
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Tools for Studying the Nervous System
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Microelectrode TechniquesVery small electrodes inserted into
individual neuronsUsed to study activity of a single neuron
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Macroelectrode TechniquesUsed to get a picture of overall activity in
the brainAn example is an EEG, which uses
electrodes placed on a person’s scalp to measure brain activity
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Structural ImagingComputerized 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
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Functional ImagingEEG imaging
electrical activity on the scalp from millions of neurons is used to produce a continuous picture of activity in the brain
Magentoencephalography (MEG) and Magnetic source imaging (MSI)Can localize activity more precisely than EEG
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Functional ImagingPositron 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
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Spinal Cord
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Spinal CordComplex 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
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Spinal CordThe spinal cord controls some protective
reflex movements without any input from the brain
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Peripheral Nervous System
Peripheral Nervous System
Somatic Nervous System Autonomic Nervous System
Sympathetic Division Parasympathetic Division
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Somatic Nervous SystemConsists of neurons that communicate
between the body and the brainAfferent neurons
Neurons that carry messages from sense organs to spinal cord
Efferent neuronsNeurons that carry messages from the spinal
cord or brain to muscles and glands
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Autonomic Nervous System Sympathetic division
Most active when you are angry, afraid, or aroused
Fight-or-flight response
Increases heart rate and breathing
Stops digestion
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Autonomic Nervous System Parasympathetic
division Calms body Produces effects
opposite to those of the sympathetic division
Reduces heart rate and breathing
Restores digestion
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Endocrine System
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Endocrine SystemHelps 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
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Endocrine System Thyroid gland
Secretes hormones (primarily thyroxin) that control metabolism
Parathyroid glands Control levels of
calcium and phosphate which in turn controls levels of excitability
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Endocrine System Pineal gland
Secretes melatonin which regulates the sleep-wake cycle
Pancreas Regulates blood-sugar
levels Secretes insulin and
glucagon
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Endocrine System Pituitary gland
Referred to as the “master gland” because it regulates many other glands
Gonads Ovaries and testes
secrete estrogens and androgens
Adrenal glands Secretes hormones in
reaction to stress
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Genes, Evolution, and Behavior
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
GeneticsHeredity - transmission of trait from one
generation to nextChromosomes
Pairs of thread like bodies that contain genesDeoxyribonucleic acid (DNA)
Organic molecule arranged in a double-helixContains the “code of life”
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Behavior Genetics Study of behavior from a genetic
perspectiveAnimal behavior genetic studies include:
Strain studiesSelection studies
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Human Behavior GeneticsFamily studies
Assume that close family members share more of a trait than non-relatives
Used to assess the heritability of psychological disorders or traits
Twin studiesUsed to determine how heritable a trait or
disorder may beIdentical twins would have highest heritability
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Human Behavior GeneticsAdoption studies
Used to assess the influence of environmentMolecular genetics
Direct study of the genetic code
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Evolutionary PsychologyNatural selection
“Survival of the fittest”Evolutionary psychology looks at the
adaptive or survival value of behaviors
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Social ImplicationsStudy of biological origins of behavior
could lead to genocide and eugenics aimed at eliminating certain types of people
Could also be used to create new categories of people, such as people bred to be good soldiers or manual laborers