Chap 3 The Biology of Behavior 07 09 2012 the mind is what the brain does Study of the structure and function of neurons nerves and nervous o and how they relate to behavior and learning The body s speedy electrochemical communication system o All the nerve sells in peripheral nervous system PNS and the Central Nervous System CNS o Neurons building blocks of internal communication Neuroscience tissue The Nervous System Nature Vs Nurture Nature the influence of our inherited genetic characteristics on our personality physical growth intellectual growth and social interactions Nurture every non genetic influence from prenatal nutrition to the people and things around us Behavioral genetics study of the relative power and limits of genetic and environmental influences on behavior nature vs nurture Genetics and Development Genetics the science of inherited traits nature Gene complexes Multiple DNA segments genes acting together to influence individual traits o genetic disorders include o sickle cell anemia o alcoholism o schizophrenia strands of specific genes arranged in 23 pairs chromosome disorders include Down Syndrome Monozygotic MZ twins aka identical twins zygote splits into two separate but identical masses of cells o Identical genetics and in utero environment Dizygotic DZ twins aka fraternal twins o two eggs are separately fertilized by different sperm o Genetically different but with identical in utero environment Chromosomes Twin Studies Twin studies method for studying the effects of nature vs nurture on a variety of traits MZ vs DZ twins raised together AND MZ vs DZ twins raised apart Examine how similarities and differences in genes and environments can influence behaviors Example how do variations of the dopamine receptor gene in DZ twins nature raised in the same OR different socioeconomic strata nurture influence anxiety and depression behaviors Epigenetics How environmental events influence how and when genes are activated or deactivated heritable changes in gene function that occur without a change in the DNA sequence Normally provides stable repression of unneeded genes in certain cells BUT Environmental triggers can misdirect epigenetic controls and cause disease e g cancer schizophrenia Overview of Nervous System The extensive network of specialized cells that carry information to and from all parts of the body the body s speedy electrochemical communication system all the nerve cells in the peripheral nervous system PNS and the central nervous system CNS Neural Communication Neurons building blocks of internal communication o 100 to 200 billion neurons in the brain alone Structure of the Neuron basic cell that makes up the nervous system o receives and sends messages within that system o Average neuron has between 1000 and 10000 contacts o Some neurons in the cerebellum receive 150 000 contacts Anatomy of a neuron Dendrite o bushy branching extensions of a neuron that receive messages from other neurons and conduct them to the soma cell body o receive message of fire or don t fire Anatomy of a neuron cont Soma main body of a neuron o Responsible for life of the cell its metabolic center o Genetic material stored here o Information neural impulses is processed here Decides weather to fire or not fire Fire pass the message on Do not fire don t pass the message on Neurotransmitters Axon tail of a neuron o long tube like structure that carries the neural message to be sent to other neurons o Action potential travels down the axon to the axon terminals o Electrical signal in the axon Triggered when soma collects enough fire messages from the dendrites Only happens when the threshold of stimulation is reached If stimulation is below threshold no fire msg Neurons must be turned on and off o Inhibitory NT cause receiving cell to stop firing o Excitatory NT cause receiving cell to start firing hyperpolarization depolarization Resting potential negatively charged state of the neuron when NOT firing a neural impulse o It is polarized with a negative charge inside and positive outside Action potential positively charged state during the neural impulse the electrical message FIRE the bump in a heart monitor The Action Potential o Depolarization occurs Refractory period during return to resting potential the neuron cannot fire dip right after action potential o Hyperpolarization occurs All or none like a firing gun the neuron either fires completely or it does not fire at all does NOT vary in strength or intensity Travels down the axon between 2 and 200 mph o Why different Because different types of cells pain etc Speed of Action Potential Myelin MY uh lin fatty coating on axons o insulates protects and speeds up the neural impulse More myelin more speed Why is myelin so critical o MS o CMT too much myelin when signal gets sent gets clogged o FoF fight or flight Body supplies you with everything you need to make a quick ass decision Tons of myelin o Long Term potentiation your cells learn to fire quicker and in such have faster reaction times The neural basis of memory Increases efficiency in neural communication by partially depolarizing the cell Happens by having a slight depolarization instead of 7 it might raise to 5 so that it doesn t take as much to hit the threshold to cause the reaction Anatomy of a neuron Axon terminals o End of the axon and beginning of the junctions with other cells where messages are transferred via chemicals called neurotransmitters NTs o electrical signal from axon triggers a chemical release from Synaptic knob rounded areas on the end of axon terminals that the axon terminals contain synaptic vesicles Synaptic vesicles sac like structures found inside the synaptic knob that contain the chemical NTs Synapse SIN apps tiny gap NTs travel from the axon terminals to the next neuron s dendrites neurotransmitters NTs chemicals that transmit the message on to the next neuron what part Synaptic Communication Receptor sites holes in the surface of the dendrites or muscles or glands of the receiving cell shaped to fit a specific NT Receptor site is like a lock NT is like a key Neurotransmitters Acetylcholine movement excitatory Serotonin mood excitatory GABA inhibition sleep inhibitory Glutamate memory excitatory Norepinephrine arousal excitatory Dopamine pleasure excitatory Endorphins pain relief excitatory Chemicals and the Brain Other chemical substances can also affect neuronal communication o Agonists mimic or enhance the effects of a natural NT