Unit 3 Biology of the Brain

Transcription

1 Unit 3 Biology of the Brain Module 9 Biological Psychology and Neurotransmission To think, feel or act without a body would be like running without legs Biological Psychologists Scientific study the links biology (genetics, neural, hormonal) and psychological processes Early Models Phrenology- study of bumps on skull could reveal mental abilities and personality traits Localization of Function various brain regions have different functions

2 Neural Communication Neuron

3 Neural Communication Dendrites Listen, Axons Speak Axons can be long, up to several feet long Axons encased in Myelin Sheath, a layer of fatty tissue insulates wiring and speeds impulses Sheath is laid down until age 25, helping neural efficiency, judgement and self control Multiple Sclerosis: degeneration of myelin sheath; communication to muscles slows with eventual loss of muscle control

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5 Transmission Action Potential neural impulse, a brief electrical charge that travels down the axon (travel is between 2 and 180 mph) Neurons generate electricity from chemical events; chemistry to electricity process Ions (electrically charged atoms) are exchanged Outside axon is POSTIVE charge, inside axon is NEGATIVE charge Positive outside/negative inside state is called Resting Potential When resting the membrane of the axon is selectively permeable; allowing only certain ions into its gates Once a neuron fires, gates open one after another allowing the positive ions to flood into the axon Refractory Period is when the neuron pumps the positively charged sodium ions outside

6 Transmission Neural signals can be excitatory (accelerator) or inhibitory (slowing) Impulse must reach Threshold to signal action potential Level of stimulation needed to trigger response Increase stimulation above threshold will not increase neural response; its All or Nothing Response system fires full strength or not at all Neurons Firing

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8 Neurotransmitters, Motions and Emotions A brain pathway may use only one or two neurotransmitters Particular neurotransmitters affect specific behaviors and emotions They don t operate in isolation, they interact and their effects vary with the receptors they stimulate

9 Endorphins - naturally occurring neurotransmitter similar to morphine Exercise releases runner s high One problem with using opiates, the brain may stop producing its own natural opiates Drugs and other chemicals affect brain chemistry at the synapses by exciting or inhibiting neuron firing - molecules mimic natural neurotransmitter

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13 Nervous System Information Travels through 3 types of neurons: Sensory Neurons carries messages from body tissue and sensory receptors inwards to the brain and spinal cord for processing Motor Neurons carries messages from central nervous system out to the body s muscles and gland Interneurons processes information between sensory input and motor output 40 Billion neurons, each connection with roughly 10,000 other neurons, we end up with somewhere around 400 trillion synapses A space equal to a grain of sand contains around 100,000 neurons and 1 billion synapses

14 Neurons cluster into NEURAL NETWORKS

15 Neural pathways govern our Reflexes, our automatic responses to stimuli

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19 Nervous System Endocrine System Released from terminals into synapses Triggered by electric impulses (nervous system) Effect behavior, digestion, reproduction, mood and metabolism Bind to specific receptor sites Released by endocrine glands into the bloodstream Chemical signals: hormones Rapid and specific delivery of message Chemical released inside our bodies Take time to have an effect; last longer than messages sent with nervous system

20 Studying the Brain, and Older Brain Structures Tools of Discovery Electroencephalogram (EEG) amplified recording of the waves of electrical activity sweeping across the brain surface measured by electrodes places on scalp Computed Tomography (CT) series of X-ray photographs taken from different angles and combined for a composite representation of a slice of the brain Positron Emission Tomography (PET) visual display of the brain that detects where a radioactive form of glucose goes when the brain is performing a certain task Magnetic Resonance Imaging (MRI) uses magnetic fields and radio waves to produce computer generated images of soft tissue

21 Older Brain Structures The Brainstem Oldest Part and Central Core Responsible for automatic survival functions Medulla base of brainstem; controls heartbeat and breathing Pons just above Medulla; helps coordinate movement Thalamus at the top of the brainstem; sensory control center (hub of sensory traffic), directs messages to sensory receiving area in the cortex and transmits replies to cerebellum and medulla The Reticular Formation nerve network that travels through the brainstem and thalamus and play important role in controlling arousal The Cerebellum extending from the rear of the brainstem little brain ; non verbal learning and memory, judge time, modulate emotion and discriminate sound and textures; can coordinate voluntary movement

22 THE LIMBIC SYSTEM Between the oldest and newest parts of the brain Amygdala two lima bean sized clusters linked to emotion; linked to aggression and fear (includes perception of emotions and processing of emotional memories Hypothalamus directs several maintenance activities: eating, drinking, body temperature, endocrine system, linked to emotion and reward Reward Deficiency Syndrome may be a the root of many addiction disorders

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24 Cerebral Cortex Cerebral Cortex thin surface layer of interconnected neural cells; thinking crown; ultimate control center *compared to bark on a tree - our ability to think and adapt, and not operate on rigid genetic instructions, is a result of the larger cortex mammals have Structure of the Cortex- contain around 20 to 23 billion nerve cells and 300 trillion synaptic connections. Glial Cells - glue cells, or worker bees, that feed and sheath these cells play a role in learning and thinking by chatting with neurons they participate in information transmission and memory

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27 Brain Computer Interface use of electrodes to decode cognitive neural signals to control an external device, such a robotic arm

28 Association Areas all the cortical areas (visual, auditory, motor, sensory) occupy about ¼ of the brain cortex - intelligent animals have increased amounts of uncommitted space, called association areas. These vast areas of the brain are responsible for interpreting, integrating and acting on sensory information and linking it with information stored Broca s Area controls speaking Wernicke s Area controls comprehension

29 Brain Plasticity the ability of the brain to reorganize and repair itself after damage Research on brain damage has revealed two things: - severed neurons usually do not regenerate - some brain functions are preassigned to specific areas Ability to repair itself relies on building new pathways or producing new brain cells Neurogenesis- formation of new neurons

30 MODULE 13 Brain Hemisphere Organization & The Biology of Consciousness 1. Our Divided Brain Lateralization the similar looking left and right side of the brain serve different functions Corpus Callosum- wide band of axon fibers that connects two hemispheres of the brain carries messages between them Split Brain result of surgery to cut fibers connected two sides of the brain

31 Sperry and Gazzaniga Study found that people with split brain condition have two separate minds. When the two minds are at odds, the left hemisphere does the mental work of rationalizing reactions Gazzaniga concluded that the conscious left hemisphere is an interpreter that constantly constructs theories to explain our behavior

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33 Right / Left Differences Intact Left Language: Speech - Quick, literal interpretation Calculations - Mathematical, Logical, Analytical Right Language: Inferences - Clear Meaning - Sense of Self Handedness - 90% right handed; 10% left handed (mostly boys) Left handers are more numerous than usual with reading disabilities, allergies and migraine headaches Left handers are more common among musicians, mathematicians, professional baseball, cricket players, architects and artists

34 2. Biology of Consciousness Consciousness - awareness of ourselves and our environment Cognitive Neuroscience - interdisciplinary study of the brain activity linked with our mental processes - used to explore and map the conscious functions of the cortex Dual Processing - information is processed on two levels, conscious and unconscious tracks - unconscious parallel processing is faster than sequential conscious processing, which involved focused attention and problem solving

35 MODULE 14 Behavior Genetics: Predicting Individual DifferencesDescribe Kinship/ Human Nature as described on page 123 Universal human attributes; shared biological heritage; common behavioral tendencies; shared brain architecture predisposes us to survive in certain ways; shared understanding of emotion Genes: Our Codes for Life Behavioral Genetics study of the power and limitations of genetic and environmental influences on behavior Chromosome- Coiled chain of DNA molecules that contain genes DNA- complex molecule containing the genetic information that makes up chromosomes Genes-biochemical bits of heredity that make up the chromosomes; segments of DNA that can synthesize protein *our genetic makeup explains our similarities and differences Human Genome-complete instructions for making an organism (human beings); common sequence within all human DNA

36 Twin and Adoption Studies Identical Twins vs. Fraternal Twins Allows for studies in genetics and environmental influences - Identical twins share same genes, not the same number of copies of those genes - same genes can translate into shared experiences - Alzheimer's disease in one twin will present a 60% chance of getting the disease in identical twin; 30% in a fraternal twin - Identical twins often share a placenta, but when they don t it can contribute to developmental differences - Identical twins are more likely to share personality traits than fraternal twins Separated Twins Findings Twins separated at birth show similarities in tastes, physical attributes, personality, abilities, attitudes, interest and fears Biological vs. Adoptive Relatives Findings People who grow up together, where biologically related or not, do not much resemble one another in personality *shared environment has virtually no discernible impact on personality - Parents do influence children s attitudes, values, manners, faith and politics

37 The New Frontier: Molecular Genetics Molecular Genetics subfield of biology that studies the molecular structure and functions of genes - genetic tests can reveal at risk populations for many diseases Heredity Heritability proportion of variation among individuals that was can attribute to genes - heritability for intelligence is 50%; means that genetic influence explains 50% of the observed variations amongst people Gene-Environment Interaction Epigenetics study of the environmental influence on gene expression that occurs without DNA change - genes can be active or inactive; environmental factors can trigger the switch... on or off - environmental factors include: diet, drugs, stress

38 MODULE 15 Evolutionary Psychology: Understanding Human Nature 1. Evolution and Natural Selection Evolutionary Psychologists study of the evolution of behavior and the mid, using principles of natural selection Natural Selection- range of inherited traits; those contributing to reproduction and survival will most likely be passed on to succeeding generations a. Mutations random error in gene replication that lead to a change What common questions did our ancestors face? - Alleys? Enemies? What food to eat? With whom should they mate? 2. An Evolutionary Explanation of Human Sexuality Gender Differences in Sexuality Males more likely to think about and initiate sexual activity; Men have a lower threshold for perceiving warm responses as a sexual come-on Natural Selection & Mating Preferences- to sum it up females pair wisely, men pair widely; men find healthy, youthful appearance attractive (indicates fertility) women pair for long term; seek mates that support and protect the family

39 3. Reflections on Nature vs. Nurture Diagram the Biopsychosocial View of Individual Development According to Sperry, where does the mind come from? From the brain that in turn influences the mind