Biopsychology Chapter 3

Brain Basics  About the size of a grapefruit  Weighs about 3 lbs.  Has a pinkish/gray wrinkled surface  The home of some 100 billion nerve cells. Each making connections with up to 10 thousand nerve cells  Most complex structure known to man  It’s cells out number ALL the stars in the galaxy

Development Stages  At birth: the brain has an extra supply of nerve cells. Many die in our first few years.  Adolescence: The brain cell number stabilizes.  Adulthood: Our brains generate some new nerve cells throughout our lives, but the total remains basically constant.  New cells in our brain do expire at a low rate!  200,000, will die everyday of your adult life. But b/c we start off with so many we still have 98% of our cells at age 70!

Brain Capabilities  Regulates our body functions  Control over our behavior  Generates our emotions and desires  Process the experiences of a lifetime  Brain has the ability to think about itself  Brain has circuits capable of producing emotions, motives, and insights.

What is biopsychology?  Biopsychology  The specialty in psychology that studies the interaction of biology, behavior, and the environment  Neuroscience – Interdisciplinary field that focuses on the brain and its role in psychological processes

Biopsychology  How are genes and behavior linked?  Innate (inborn) abilities!  Examples of innate abilities:  At birth we are “programmed” for language, social interaction, and self preservation.  How does this happen/change?  Evolution: the process by which succeeding generations of organisms change as they adapt to a changing environment.  Ex: adapting to new diseases

Charles Darwin  He was originally trained for medicine and ministry. But decided biology was his calling.  1831 : signed on as a naturalist about the HMS Beagle to survey the coastline of South Africa.

5 years later…  He returned from the HMS Beagle. He brought home the radical idea of relationship among species.  He observed organisms exquisitely adapt to their environments  He observed variation among individuals within species (finches beaks)

Natural Selection  Natural selection – The driving force behind evolution, by which the environment “selects” the fittest organisms  “Weeding out” process individuals best adapted to the environment are more likely to flourish and reproduce.  Those who don’t adapt will most likely die out.

How Natural Selection Works… Environmental pressure Competition Selection of fittest phenotype Reproductive success Frequency of that genotype increases

Evolutionary Psychology  Fairly new to the field of psychology.  It’s pretty controversial  Nature vs. Nurture. Evolutionary Psychology places too much emphasis on nature and not enough on nurture (role of learning)  It has made sense of some things:  Human phobias : they almost always involve a stimulation that signaled danger to our ancestors. (snakes, blood, darkness)

Genetics and Inheritance  Genes: The functional units of a chromosome  Composed of nucleotides  Chromosome: tightly coiled threadlike structure along which genes are organized. (beads on a necklace)  DNA – A long, complex molecule that encodes genetic characteristics.

Genes/Chromosomes

Genes and Inheritance  Your genes encode information that can become your inherited traits.  Your height, weight, facial features, and hair color all originate in the encoded genetic “blueprint” inherited from your parents.  Many of our psychological features are inherited from our parents as well. Like our basic temperament, fears, behavior patterns..  Who can give examples?

But despite genetic heritage…  You are a unique individual!  1. Your differences lie in your experiences, in the environment in which you grew up distinct to time.  2. The random combination of traits  Each parent passed onto you genes from past generations of their family lines (eye color, skin color, personality) they are combined randomly to produce you.

Genotype  This hybrid of genetic inheritance produces your genotype.  The genetic pattern that makes you different from everyone else. “genetic blueprint”

Phenotype  Your physical characteristics, including visible traits, but also the chemistry and wiring of your brain.  Examples: hair color, facial structure

Genes and Inheritance  Mutations – Genetic variations, which occur randomly, especially during the recombination of chromosomes in sexual reproduction

Heredity  How your genes are passed down.  Heredity never acts alone but always in partnership with the environment.  Example: biological influences like nutrition, diseases, and stress.  Poor medical care can result in a birth defect.

Chromosomes, Genes, DNA  Human makeup:  DNA contains approximately 30,000 genes  Your genes reside on 46 chromosomes that are arranged in 23 pairs.  One in each pair comes from each parent. (The genes are randomly shuffled)

Sex Chromosome  The X and Y chromosomes that determine our physical sex characteristics  Named “X” and “Y” for their shape  These chromosomes carry genes encoding for male or female phenotype  “X” chromosome comes from the mother  “y” chromosome comes from the father  When paired: “XX” is the phenotype for a female, “XY” is the phenotype for male  Chromosomes from the biological father determine the baby’s sex.

How does the body communicate internally?  The brain coordinates the body’s 2 communication systems  1. The Nervous System  2. The Endocrine System  Both systems use similar chemical processes to communicate with targets throughout the body.

Terms  Neurons: a cell specialized to receive, process and transmit information to other cells.  Three types: sensory, motor, interneurons

Sensory (afferent) Neurons  One way streets that carry traffic from the sense organs towards the brain.  They tell the brain all your sensory experiences; vision, taste hearing, touch, smell, pain, balance.

Motor (efferent) Neurons  One way streets that transport messages away from the brain to the muscles, organs, and glands.

Interneurons  Sensory and motor neurons rarely communicate directly with one another.  They rely on the interneurons, “the go between”  They relay messages from sensory neurons to other interneurons or to motor neurons.  Example: Shower: You use your hand to check the water temperature. Sensory neurons carry the sensation to the brain. Motor neurons deliver the message from the brain about the temperature.

Structure of a Neuron

Neural Impulses  Neural impulse – Brief electric surge that carries the neuron ’ s message  Ions – Charged particles that are moved across the cell membrane

How Neurons work:  Dendrites : finely branched fibers that extend outward from the cell body.  They accept incoming messages.  They act like a net, collecting messages received by direct stimuli,

How Neurons work:  Soma: Cell Body  Dendrites complete their job by passing incoming messages to the soma.  The soma contains the cell’s nucleus and accesses all the messages received/collected from the dendrites.

The Neural Impulse  Action Potential  Resting Potential  Synapse  Synaptic Transmission

How Neurons Work:  A typical neuron receives 1,000’s of messages from other neurons. But, if the messages get relayed it depends on 2 things.  1. Excitatory  fire  2. Inhibitory  Don’t fire  When excitation trumps inhibitory the neuron generates a message of its own and sends it through an axon.  Axon: is single transmitter fibers

Action Potential  Nerve cells employ both electrical and chemical signals to process and transmit information.  Ions: Axon gets its electrical energy to transmit information through these charged chemicals.  When the cell body becomes excited it triggers a cascade of events that temporarily reverse the charge and cause an electrical signal to race along the axon

Resting Potential  “Normal State” of a neuron  During this state ions within the cell give the axon a small negative charge.  *This resting potential state in-balance can be easily upset*

In Balance upset when…  During action potential, when the cell body becomes excited it triggers a cascade of events that temporarily reverse the charge and cause an electrical signal to race along the axon

Axon Principles  All or none principle:  Either the axon “fires or it doesn’t, there is no in-between.”

Axons-Synaptic Transmission:  Synaptic Transmission:  There is a remarkable sequence of events, the electrical message morphs into a chemical message that flows across the synaptic gap btw neurons  Synaptic Transmission  Synapse : acts as an electrical insulator, preventing the charge speeding down the axon from jumping to the next cell. (Synaptic Gap)  To pass the message across the synaptic gap a neuron must initiate a process in a tiny bulb structure  terminal buttons  Terminal buttons: are found at the ends of the axons.

Synaptic Vesicles (SACS)  Contain neurotransmitter molecules that connect the presynaptic membrane, releasing the neurotransmitter into the synapse.

Neurotransmitters  Chemical messengers that relay neural messages across the synapse.

7 Important Neurotransmitter  Dopamine  Serotonin  Norepinephrine  Acetylcholine  Gaba  Glutamine  Endorphins

Dopamine  Produces sensations of pleasure and reward; used by CNS neurons in voluntary movement  Problems with imbalance:  Schizophrenia, Parkinson’s disease  Substances that Affect:  Cocaine, amphetamines, Ritalin, alcohol

Serotonin  Regulates sleep and dreaming, mood, pain, aggression, appetite and sexual behavior  Problems with imbalance:  Depression, certain anxiety disorders, obsessive-compulsive disorder  Substance that Affect:  Prozac, hallucinogenics (e.g. LSD)

Norepinephrine  Controls heart rate, sleep, sexual responsiveness, stress, vigilance and appetite  Problems with imbalance:  High blood pressure, depression  Substances that Affect:  Tricyclic antidepressants, beta blockers

Acetylcholine  Primary transmitter used by neurons carrying messages from CNS; involved in some kinds of learning and memory  Problems with imbalance:  Certain muscular disorders, Alzheimer’s disease  Substances that Affect:  Nicotine, botulism toxin, curare, atropine

GABA  Most prevalent inhibitory neurotransmitter in neurons of CNS  Problems with imbalance:  Anxiety, epilepsy  Substances that Affect:  Barbiturates, tranquilizers (e.g. Valium, Librium), alcohol

Glutamine  Primary excitatory neurotransmitter in CNS; involved in learning and memory  Problems with imbalance:  Brain damage after stroke  Substances that Affect:  PCP (“angel dust”)

Endorphins  Pleasurable sensations and control of pain  Problems with imbalance:  Lowered levels resulting from opiate addiction  Substances that Affect:  Opiates: opium, heroin, morphine, methadone

Process  1.Vesicles spill contents  2.Transmitter molecules diffuse across the synaptic gap  3.If they have the right shape of the target key receptor the message is carried forward  After the transmitter molecules have done their work, they are broken down and recycled back to the terminal buttons=REUPTAKE

Plasticity Neurons  Have the ability to change. They make new connections or strengthen old ones.  The nervous system has the ability to adapt or modify itself based on experience.  Example: Brains ability to compensate for injury (stroke)  “Brain is reprogrammed: by experience

Plasticity Neurons  Have the ability to change. They make new connections or strengthen old ones.  The nervous system has the ability to adapt or modify itself based on experience.  Example: Brains ability to compensate for injury (stroke)  “Brain is reprogrammed: by experience  LM

Glial Cells  “Glue neurons” together!  They provide structural support for neurons, as well as help from new synapses.  Glial cells form a myelin sheath, a fatty insulation around the spinal cord and axons in the brain.  Protects the cell and helps speed the conduction of impulses along the axon.  MS attacks the myelin sheath