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Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Biological Basis of Behavior
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Neurons: The Messengers
About 100 billion neurons (nerve cells) in the human brain
Neurons 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 Cells
Cells 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 Impulse
PolarizationWhen 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 Synapse
Synaptic space (synaptic cleft)Tiny gap between neurons
Terminal button Enlarged area at the end of an axon
The synapseComposed 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
Psychopharmacology
Most 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
Psychopharmacology
CocainePrevents reabsorption of dopamineLeads to heightened arousal of entire nervous
system
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Neural Plasticity
The brain can be changed, both structurally and chemically, by experience
Rat 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 Core
Reticular formationNetwork of neurons found throughout the
brainServes 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 hemispheres
Each hemisphere appears to specialize in certain functions
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Split-Brain Research
Much 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 Techniques
Very small electrodes inserted into individual neurons
Used to study activity of a single neuron
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Macroelectrode Techniques
Used to get a picture of overall activity in the brain
An 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 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
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Functional Imaging
EEG imagingelectrical 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 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
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 Cord
Complex cable of nerves that connects brain to rest of the body
Carries motor impulses from the brain to internal organs and muscles
Carries sensory information from extremities and internal organs to the brain
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
The Spinal Cord
The 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 System
Consists of neurons that communicate between the body and the brain
Afferent neuronsNeurons that carry messages from sense
organs to spinal cordEfferent neurons
Neurons 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 System
Helps coordinate and integrate complex psychological reactions
Endocrine glands secrete hormones into the bloodstream
Hormones serve to organize the nervous system and body
Hormones 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
Genetics
Heredity - transmission of trait from one generation to next
ChromosomesPairs of thread like bodies that contain genes
Deoxyribonucleic 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 perspective
Animal behavior genetic studies include:Strain studiesSelection studies
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
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 studies
Used to determine how heritable a trait or disorder may be
Identical twins would have highest heritability
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Human Behavior Genetics
Adoption studiesUsed to assess the influence of environment
Molecular geneticsDirect study of the genetic code
Psychology: An IntroductionCharles A. Morris & Albert A. Maisto
© 2005 Prentice Hall
Evolutionary Psychology
Natural 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 Implications
Study 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