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) OF THE NEXT NEURON

• 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.