3. biological foundations of behavior

Psychology: An IntroductionCharles A. Morris & Albert A. Maisto

© 2005 Prentice Hall

The Biological Basis of Behavior



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



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



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



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

Ions Charged molecules

Resting Potential When more negative

ions are inside the neuron than outside

Charge is approximately -70mV

Neuron 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 Potential Sudden, massive

change in charge in the neuron

Occurs when depolarization reaches the threshold of excitation

Ions flow across cell membrane



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



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



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



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



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



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



Psychopharmacology

CocainePrevents reabsorption of dopamineLeads to heightened arousal of entire nervous

system



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



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



Central Nervous System

Central Nervous System

Brain Spinal Cord



The Brain – The Central Core

Medulla Controls breathing,

heart rate, and blood pressure

Pons Maintains the sleep-

wake cycle

Cerebellum Coordinates body’s

movements




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




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 hemispheres

Important to learning and emotional behavior Hippocampus essential in

formation of new memories Amygdala, together with

the hippocampus, is important for regulating emotions



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



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



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



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 neurons

Used to study activity of a single neuron



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



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 brain

Magentoencephalography (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 body

Carries motor impulses from the brain to internal organs and muscles

Carries 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

Peripheral Nervous System

Somatic Nervous System Autonomic Nervous System

Sympathetic Division Parasympathetic Division



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



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



The Autonomic Nervous System

Parasympathetic division Calms body Produces effects

opposite to those of the sympathetic division

Reduces heart rate and breathing

Restores digestion



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




Thyroid gland Secretes hormones

(primarily thyroxin) that control metabolism

Parathyroid glands Control levels of

calcium and phosphate which in turn controls levels of excitability




Pineal gland Secretes melatonin

which regulates the sleep-wake cycle

Pancreas Regulates blood-sugar

levels Secretes insulin and

glucagon




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



Genes, Evolution, and Behavior



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”



Behavior Genetics

Study of behavior from a genetic perspective

Animal 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 studies

Used to determine how heritable a trait or disorder may be

Identical twins would have highest heritability



Human Behavior Genetics

Adoption studiesUsed to assess the influence of environment

Molecular geneticsDirect study of the genetic code



Evolutionary Psychology

Natural selection“Survival of the fittest”

Evolutionary 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 people

Could also be used to create new categories of people, such as people bred to be good soldiers or manual laborers

3. biological foundations of behavior

Education

prentice hall neurons

morris albert

introduction charles

prentice hall transmission

neurons unique

support neurons

neurons terminal button

neurons nerve cells