THE BIOLOGICAL BASIS
OF BEHAVIOR
CHAPTER 2
NEURONS:
THE MESSENGERS
SECTION 1
WHAT “LANGUAGE” DO NEURONS SPEAK?
• THE AVERAGE HUMAN BRAIN CONTAINS AS MANY AS 100
BILLION NERVE CELLS, OR NEURONS
• NEURONS VARY WIDELY IN SIZE IN SHAPE, BUT THEY ARE ALL
SPECIALIZED TO RECEIVE AND TRANSMIT (SEND) INFORMATION
• LIKE ALL CELLS, THEY ARE MADE UP OF:
• NUCLEUS : THE COMPLETE SET OF CHROMOSOMES AND GENES
• CYTOPLASM: KEEPS THE CELLS ALIVE
• CELL MEMBRANE: ENCLOSES THE WHOLE CELL
• WHAT MAKES THEM DIFFERENT?
• DENDRITES: SHORT FIBERS THAT BRANCH OUT FROM THE CELL BODY
AND PICK UP INCOMING MESSAGES
• AXON: SINGLE LONG FIBER EXTENDING FROM THE CELL BODY; CARRIES
OUTGOING MESSAGES TO OTHER NEURONS, MUSCLES OR GLANDS
• ALL NEURONS ONLY HAVE ONE AXON BUT AT THE END THEY BRANCH
OFF INTO MANY TERMINAL BRANCHES
• NERVES: GROUP OF AXONS BUNDLED TOGETHER LIKE WIRES
• MYELIN SHEATH: WHITE, FATTY COVERING AROUND THE
AXON PINCHED IN INTERVALS
• TWO FUNCTIONS:
• PROVIDES INSULATION SO SIGNALS FROM ADJACENT
NEURONS SO THEY DO NOT INTERFERE WITH EACH
OTHER
• INCREASES THE SPEED THAT A SIGNAL IS TRANSMITTED
OTHER NEURONS
• SENSORY NEURON: NEURONS THAT COLLECT MESSAGES FROM SENSE
ORGANS AND CARRY THEM TO THE SPINAL CORD OR THE BRAIN
• MOTOR NEURONS: NEURONS THAT CARRY MESSAGES FROM THE SPINAL
CORD/BRAIN TO MUSCLES AND GLANDS
• INTERNEURONS (ASSOCIATION) NEURONS: CARRIES MESSAGES FROM ONE
NEURON TO ANOTHER
• THE NERVOUS SYSTEM ALSO CONTAINS NUMEROUS GLIAL CELLS OR GLIA
• GREEK WORD FOR GLUE
• HOLD THE NEURONS IN PLACE, PROVIDE NOURISHMENT AND WASTE
PRODUCT, PREVENT HARMFUL SUBSTANCES FROM PASSING FROM THE
BLOOD STREAM TO THE BRAIN, AND FORMS THE MYELIN SHEATH
NEURAL IMPULSE
• NEURONS “SPEAK” WITH SIMPLE ELECTROCHEMICAL IMPULSES
• WHEN A NEURON IS AT REST AND NOT “SPEAKING” THEY ARE IN A STATE OF
POLARIZATION—THE CONDITION OF A NEURON WHEN THE INSIDES IS
NEGATIVELY CHARGED OUTSIDE
• A GUITAR STRING THAT HAS BEEN PULLED BUT NOT RELEASED
• TO GENERATE A SIGNAL THE TENSION NEEDS TO BE RELEASE
• DEPOLARIZATION : WHEN AN AREA OF THE CELL MEMBRANE IS
STIMULATED ENOUGH BY MESSAGES , PORES (CHANNELS) ALLOW
POSITIVELY CHARGED IONS COME IN; ALLOWING THE INSIDE TO BE
POSITIVE
• CREATES AN ELECTRICAL CHARGE, OR A NEURAL IMPULSE, THAT
TRAVELS DOWN THE AXON
• WHEN THIS HAPPENS THE NEURON HAS “FIRED”—SENT A SIGNAL
• THIS ENTIRE PROCESS TAKES ONLY A MILLISECOND
• GRADED POTENTIAL : INCOMING MESSAGES THAT CAUSE A
SMALL, TEMPORARY SHIFT IN THE ELECTRICAL CHARGE
LEAVING THE NEURON IN ITS POLARIZED STATE
• FOR A NEURON TO FIRE, GRADED POTENTIALS MUST
EXCEED A CERTAIN MINIMUM THRESHOLD OF
EXCITATION—LEVEL AN IMPULSE MUST EXCEED TO CAUSE
A NEURON TO FIRE
• EACH TIME A NEURON FIRES IT IS THE SAME STRENGTH
• CALLED ALL-OR-NOTHING- LAW
• HOWEVER, THE NEURON IS MORE LIKELY TO FIRE MORE OFTEN WHEN
STIMULATED BY A STRONG SIGNAL
• ABSOLUTE REFRACTORY PERIOD: AFTER A NEURON FIRES, FOR THE
NEXT THOUSANDTH OF A SECOND IT WILL NOT FIRE AGAIN REGARDLESS
OF THE STRENGTH OF THE INCOMING MESSAGE'S
• RELATIVE REFRACTORY PERIOD: DURING THE RESTING STATE OF A CELL
THE NEURON WILL ONLY FIRE IF THE INCOMING MESSAGE IS
CONSIDERABLY STRONGER THAN NORMAL
• OTHERWISE AFTER A NEURON FIRES IT RETURNS TO ITS RESTING STATE
AND WAITS FOR THE NEXT INCOMING MESSAGE
THE SYNAPSE
• NEURONS ARE NOT DIRECTLY CONNECTED LIKE A CHAIN, INSTEAD THERE
ARE TINY GAPS—CALLED SYNAPTIC SPACE
• WHEN A NEURON FIRES, AN IMPULSE TRAVELS DOWN THE AXON, OUT
THOUGH THE TERMINAL BRANCHES INTO A TINY SWELLING THAT LOOKS
LIKE A LIGHT BULB
• CALLED TERMINAL BUTTON OR SYNAPTIC KNOB
• SYNAPSE: AREA COMPOSED OF THE AXON TERMINAL OF ONE
NEURON, THE SYNAPTIC SPACE, AND THE DENDRITE (CELL BODY)
THE NEXT NEURON
OF
• WHEN THE NEURAL IMPULSES REACHES THE END OF THE TERMINALS IT CAUSES
THE VESICLES TO RELEASE VARYING AMOUNTS OF CHEMICALS CALLED
NEUROTRANSMITTERS
• SYNAPTIC VESICLES: TINY BAGS IN THE TERMINAL BUTTON THAT RELEASE
CHEMICALS INTO THE SYNAPSE
• NEUROTRANSMITTERS: CHEMICALS RELEASED BY THE SYNAPTIC VESICLES THAT
TRAVEL ACROSS THE SYNAPTIC SPACE
• NEUROTRANSMITTERS EACH HAVE A SPECIFIC MATCHING RECEPTOR SITE ON THE
OTHER SIDE OF THE SYNAPTIC CELL
• RECEPTOR SITE: LOCATION ON A RECEPTOR NEUROTRANSMITTER; FITS LIKE A
KEY INTO A LOCK
• ONCE THEIR JOB IS DONE THEY DETACH FROM THE RECEPTOR SITE
• RECYCLED TO MAKE NEW NEUROTRANSMITTERS, OR DISPOSED IN THE
BODY AS WASTE
NEUROTRANSMITTERS
• THERE ARE HUNDREDS OF NEUROTRANSMITTERS, BUT THEIR EXACT FUNCTION IS STILL UNKNOWN
• SOME NEUROTRANSMITTERS ARE:
• ACETYLCHOLINE: INVOLVED IN AROUSAL, ATTENTION, MEMORY, MOTIVATION, AND
MOVEMENT.
• CAN LEAD TO ALZHEIMER’S DISEASE
• DOPAMINE: VARIETY OF BEHAVIORS AND EMOTIONS, INCLUDING PRESSURE.
• IMPLICATED IN SCHIZOPHRENIA AND PARKINSON’S DISEASE
• SEROTONIN: REGULATES SLEEP, DREAMING, MOOD, EATING, PAIN, AND AGGRESSION
• IMPLICATED IN DEPRESSION
• ENDORPHINS: INHIBITION OF PAIN, RELEASED DURING STRENUOUS EXERCISE
• RESPONSIBLE FOR “RUNNER’S HIGH”.
PSYCHOPHARMACOLOGY
• MOST PSYCHOACTIVE DRUGS AND TOXINS WORK BY EITHER BLOCKING OR
ENHANCING THE TRANSMISSION OF CHEMICALS ACROSS SYNAPSES
• OTHERS DO THE EXACT OPPOSITE
• ENHANCE ACTIVITY FOR NEUROTRANSMITTERS
• INCREASING THE RELEASE OF TRANSMITTER
• SOME SUBSTANCES INTERFERE WITH THE REMOVAL OF
NEUROTRANSMITTERS FROM THE SYNAPSE AFTER THEY HAVE DON’T THEIR
JOB SO THAT THEY CAN STIMULATE RECEPTOR NEURONS
• EX: COCAINE—PREVENTS DOPAMINE FROM BEING
REABSORBED…LEAD TO THE EXCESS AMOUNTS OF DOPAMINE IN YOUR
SYSTEM
NEURAL PLASTICITY
• NEURAL PLASTICITY: THE ABILITY OF THE BRAIN TO CHANGE IN RESPONSE TO
THE EXPERIENCE
• FEEDBACK LOOP—EXPERIENCE LEAD TO CHANGES IN THE BRAIN, WHICH
FACILITATE NEW LEARNING…WHICH LEADS TO THE BRAIN CHANGING TO
ACCEPT WHAT WE NEWLY LEARNED
• EX: DEAF PEOPLE’S BRAINS HAVE SHOWN CHANGES IN THE AREAS
RESPONSIBLE FOR HEARING TO REWIRED TO READ LIPS AND SIGN
LANGUAGE
• STUDIES DONE IN THE 1990’S SHOWED THAT ADULT BRAINS ERE CAPABLE OF
NEUROGENESIS– GROWTH OF NEW NEURONS
THE CENTRAL NERVOUS
SYSTEM
SECTION 2
ORGANIZATION OF THE NERVOUS SYSTEM
• EVERY PART OF THE CENTRAL NERVOUS SYSTEM IS CONNECTED TO EVERY
OTHER PART
• 2 PARTS
• THE CENTRAL NERVOUS SYSTEM INCLUDES THE BRAIN AND SPINAL CORD
• CONTAINS 90% OF THE BRAIN’S NEURONS
• THE PERIPHERAL NERVOUS SYSTEM CONSISTS OF THE NERVES THAT
CONNECT THE BRAIN AND SPINAL CORD TO EVERY OTHER PART OF THE
BODY
• CARRIES MESSAGES BACK AND FORTH BETWEEN THE CENTRAL
NERVOUS SYSTEM AND THE SENSE ORGANS, MUSCLES AND GLANDS
• SUBDIVIDED INTO 2 OTHER PARTS
•SOMATIC NERVOUS SYSTEM: TRANSMITS INFORMATION ABOUT
THE BODY MOVEMENTS AND EXTERNAL ENVIRONMENT
•AUTOMATIC NERVOUS SYSTEM: TRANSMITS INFORMATION TO
AND FROM THE INTERNAL ORGANS AND GLANDS
THE BRAIN
• PLACE WHERE LEARNING. MEMORY, AND EMOTIONS ARE CENTERED
• DECIDED WHAT TO DO AND WHETHER THE DECISION
WAS RIGHT OR WRONG
• IMAGINES HOW THINGS MIGHT HAVE BEEN IF WE HAD ACTED DIFFERENTLY
• 3 LAYERS OF THE BRAIN
• CENTRAL CORE
• LIMBIC SYSTEM
• CEREBRAL HEMISPHERES
• THE CENTRAL CORE
• AT THE POINT WHERE THE SPINAL CORD ENTERS THE SKULL, IT BECOMES THE
HINDBRAIN
• EARLIEST PART OF THE BRAIN TO EVOLVE
• PARTS AND FUNCTIONS
• MEDULLA: REGULATES RESPIRATION, HEART RATE, AND BLOOD
PRESSURE
• PONS: REGULATES SLEEP/WAKE CYCLE
• CEREBELLUM: REGULATES REFLEXES AND BALANCE, AND
COORDINATES MOVEMENT
• THALAMUS: MAJOR SENSORY RELAY CENTER, AND REGULATES THE
BRAIN CENTERS
AND THE PERIPHERAL NERVOUS SYSTEM
• HYPOTHALAMUS: EMOTIONS AND MOTIVATIONS, AND STRESS
REACTIONS
• THE LIMBIC SYSTEM
• RING OF STRUCTURES THAT PLAY A ROLE IN LEARNING AND
EMOTIONAL BEHAVIOR
• PARTS AND FUNCTIONS
• HIPPOCAMPUS: FORMATION OF NEW MEMORIES
• AMYGDALA: GOVERNS EMOTIONS RELATED TO SELF
PRESERVATION
• THE CEREBRAL CORTEX
• OUTER SURFACE OF THE 2 CEREBRAL HEMISPHERES THAT
REGULATES COMPLEX BEHAVIOR
• PROCESSES THOUGHT, VISION, LANGUAGE, MEMORY,
AND EMOTIONS
• WHAT MOST PEOPLE THINK OF WHEN WE THINK OF THE
BRAIN
• DIVIDED INTO 2 HEMISPHERES, LEFT AND RIGHT
• EACH HEMISPHERE IS DIVIDED INTO 4 LOBES
• FOUR LOBES
• OCCIPITAL LOBE
• RECEIVES AND PROCESSES VISUAL INFORMATION
• TEMPORAL LOBE
• SMELL, HEARING, BALANCE AND EQUILIBRIUM, EMOTION AND
MOTIVATION,
SOME LANGUAGE COMPREHENSION, AND COMPLEX VISUAL
PROCESSING
• FRONTAL LOBE
• GOAL-DIRECTED BEHAVIOR, CONCENTRATION,
EMOTIONAL CONTROL AND TEMPERAMENT, MOTOR
PROJECTION AND ASSOCIATION AREAS,
COORDINATES MESSAGES FROM OTHER LOBES,
COMPLEX PROBLEM
SOLVING, AND INVOLVED
IN MANY ASPECTS OF PERSONALITY
• PRIMARY MOTOR CORTEX: SECTION OF THE FRONTAL
LOBE RESPONSIBLE FOR VOLUNTARY MOVEMENT
HEMISPHERIC SPECIALIZATION
• HUMANS HAVE A “RIGHT HALF-BRAIN” AND A “LEFT HALF- BRAIN”
• CORPUS CALLOSUM: THICK BAND OF NERVE FIBERS CONNECTION
THE LEFT AND RIGHT CEREBRAL CORTEX
• LANGUAGE
• LEFT HEMISPHERE
• TOW MAJOR LANGUAGE AREAS ARE BROCA’S AREA
AND WERNICKE’S AREA
• WERNICKE’S AREA IS IN THE BACK OF THE
TEMPORAL LOB
•PROCESSES AND UNDERSTANDS WHAT OTHER ARE
SAYING, AND OVERALL LISTENING
• BROCA’S AREA FOUND IN THE FRONTAL LOBE
•ESSENTIAL IN OUR ABILITY TO TALK
• COGNITIVE AND EMOTIONAL STYLE
• LEFT SIDE OF THE BRAIN DOMINATES THE VERBAL TASKS, SUCH AS
IDENTIFYING SPOKEN AND PRINTED WORDS AND SPEAKING
• ALSO OPERATES MORE ANALYTICALLY, LOGICALLY, RATIONALLY,
AND SEQUENTIALLY
• RIGHT HEMISPHERE DOMINATES VISUAL AND SPATIAL TASKS,
NONVERBAL IMAGERY (VISUAL IMAGES, MUSIC, AD
ENVIRONMENTAL NOISES), FACE RECOGNITION, AND
PERCEPTION AND EXPRESSION OF EMOTION
• MORE INVOLVED IN SOLVING PROBLEM S THAT REQUIRE
INSIGHT OR CREATIVE SOLUTIONS
• UNIVERSITY OF WISCONSIN- MADISON STUDY
• PEOPLE WITH MORE ACTIVE LEFT FRONTAL LOBES THEN THE RIGHT FRONT
LOBES TEND TO BE MORE CHEERFUL, SOCIABLE, AND SELF CONFIDENT
• ALSO RESPOND MORE POSITIVELY TO EVENTS, ENJOY BEING AROUND
OTHER PEOPLE , AND DON’T GET UPSET OR AGGRAVATED IN
UNPLEASANT EVENTS
• MORE ACTIVE RIGHT FRONTAL LOBES ARE MORE EASILY STRESSED,
FRIGHTENED, AND UPSET AND THREATENED BY UNPLEASANT EVENTS
AROUND THEM
• THEY TEND TO SPEND MORE TIME ALONE
THE SPINAL CORD
• WE TALK OF THE BRAIN AND THE SPINAL CORD AS 2 DISTINCT
STRUCTURES, BUT IN FACT, THERE IS NO CLEAR BOUNDARY
BETWEEN THEM
• AT THE UPPER END THE SPINAL CORD ENLARGES INTO THE
BRAIN STEM
• SPINAL CORD: COMPLEX CABLE OF NEURONS THAT RUNS
DOWN THE SPINE, CONNECTING THE BRAIN TO THE MOST OF
THE REST OF THE BODY
• MADE UP OF SOFT, JELLYLIKE BUNDLES OF LONG AXONS,
WRAPPED IN INSULATING MYELIN AND SURROUNDED AND
PROTECTED BY VERTEBRAL BONES
THE PERIPHERAL NERVOUS
SYSTEM
SECTION 3
SOMATIC NERVOUS SYSTEM
• SOMATIC NERVOUS SYSTEM: PART OF THE PNS THAT CARRIES
MESSAGES FROM THE SENSE TO THE CNS AND BETWEEN THE
CNS AND SKELETAL MUSCLES
• ALL THE THINGS THAT WE SENSE—SIGHTS, SOUNDS, SMELLS,
TEMPERATURE, PRESSURE ETC.
• VOLUNTARY ACTIONS—EATING AND DRINKING, READING
AND WRITING, ETC.
AUTOMATIC NERVOUS SYSTEM
• AUTOMATIC NERVOUS SYSTEM: PART OF THE PNS THAT
CARRIES MESSAGES BETWEEN THE CNS AND THE INTERNAL
ORGANS
• CONSISTS OF 2 BRANCHES
• SYMPATHETIC
• PARASYMPATHETIC
SYMPATHETIC DIVISION
• BRANCH OF THE AUTOMATIC NERVOUS SYSTEM; IT PREPARES
THE BODY FOR QUICK ACTION IN AN EMERGENCY
• IN RESPONSE, YOUR HEART POUNDS, YOU BREATH FASTER,
YOUR PUPILS ENLARGE, AND YOUR DIGESTION STOPS
PARASYMPATHETIC DIVISION
• BRANCH OF THE AUTOMATIC NERVOUS SYSTEM; IT CALMS AND
RELAXES THE BODY
GENES, EVOLUTION,
AND BEHAVIOR
SECTION 5
GENETICS
• GENETICS: THE STUDY OF HOW LIVING THINGS PASS ON TRAITS
FROM ONE GENERATIONS TO ANOTHER
• OFFSPRING ARE NOT CARBON COPIES OF THEIR PARENTS, YET
SOME TRAITS REAPPEAR FROM GENERATION TO GENERATION IN
PREDICTABLE PATTERNS
• GENES: ELEMENTS THAT CONTROL THE TRANSMISSION OF
TRAITS; THEY ARE FOUND ON CHROMOSOMES
• CHROMOSOMES: PAIRS OF THREADLIKE BODIES WITHIN THE
CELL NUCLEUS THAT CONTAINS GENES
• HUMANS HAVE 23 PAIRS OF CHROMOSOMES IN EVERY
NORMAL CELL
• THE MAIN INGREDIENT OF CHROMOSOMES IS DNA
• DNA IS THE ONLY KNOWN MOLECULE THAT CAN
REPLICATE ITSELF
• THE HUMAN GENOME– THE TOTAL SUM OF ALL GENES IN THE
HUMAN CHROMOSOMES—CONTAINS MORE THAN 100,00
GENES
• GENES, LIKE CHROMOSOMES, OCCUR IN PAIRS
• IN SOME CASES LIKE EYE COLOR, ONE MAY BE A DOMINANT
GENE AND THE OTHER A RECESSIVE GENE
• DOMINANT: MEMBER OF THE GENE PAIR THAT CONTROLS
THE APPEARANCE OF A CERTAIN TRAIT
• RECESSIVE: MEMBER OF THE GENE PAIR THAT CAN
CONTROL THE APPEARANCE OF A CERTAIN TRAIT ONLY IF IT
IS PAIRED WITH ANOTHER RECESSIVE GENE
BEHAVIOR GENETICS
• STUDY TOPICS THAT INTEREST ALL PSYCHOLOGISTS—
PERCEPTIONS, LEARNING, MEMORY, MOTIVATION, EMOTIONS,
PERSONALITY AND PSYCH DISORDERS– BUT FROM A GENETIC
PERSPECTIVE
• GOAL IS TO DETERMINE WHICH GENES CONTRIBUTE TO
INTELLIGENCE, TEMPERAMENT, TALENTS, AND OTHER
CHARACTERISTICS
• HUMAN BEHAVIOR GENETICS
• FAMILY STUDIES: STUDIES OF HERITABILITY IN HUMANS BASED
ON ASSUMPTION THAT IF GENES INFLUENCE A CERTAIN
TRAIT, CLOSE RELATIVES SHOULD BE MORE SIMILAR ON THEIR
TRAIT THAN DISTANT RELATIVES
• EXAMPLE: SCHIZOPHRENIA
• AFFECTS 1-2 % GENERAL PUBLIC
• SIBLINGS OF PEOPLE WITH SCHIZOPHRENIA ARE 8X’S
MORE LIKELY TO DEVELOP DISORDER
• CHILDREN OF PATIENTS WITH SCHIZOPHRENIA ARE 10 X’S
MORE LIKELY TO DEVELOP DISORDER
• TWIN STUDIES: STUDIES OF IDENTICAL AND FRATERNAL TWINS TO
DETERMINE THE RELATIVE INFLUENCE OF HEREDITY AND
ENVIRONMENT ON HUMAN BEHAVIOR
• EX: NATURE V. NURTURE
• IDENTICAL TWINS: TWINS THAT DEVELOPED FROM A SINGLE
FERTILIZED OVUM AND THEREFORE IDENTICAL IN GENETIC
MAKEUP
• FRATERNAL TWINS: TWINS DEVELOPED FROM 2 SEPARATE
FERTILIZED OVA AND THEREFORE DIFFERENT IN GENETIC
MAKEUP
• ADOPTIONS STUDIES: RESEARCH CARRIED OUT ON CHILDREN,
ADOPTED AT BIRTH BY PARENTS NOT RELATED TO THEM, TO
DETERMINE THE RELATIVE INFLUENCE OF HEREDITY AND
ENVIRONMENT ON HUMAN BEHAVIOR.