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Chapter 3

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Psychology 2320A/B
Alvin Segal

Chapter 3 Psychology Nervous System - glial cells and neurons, sheathed in myein - shaping of brain = pruning, uneeded cells are eliminated o pruning, underlie decrease in gray matter that occurs in adolescence - brain + spinal = CNS - nerves outside CNS, that transmit messages = PNS o somatic: sensory organs and muscles, voluntary o autonomic: involuntary arousal and emotions  increase arousal : sympathetic  slow arousal : parasympathetic - nervous system close communication with endocrine system Brain - 3 divisions o hindbrain  pons: relay info  medulla: regulate heart function and breathing  cerebellum: movement and cognitive processing o midbrain  fibres that connect with hindbrain  reticular activating system : influences arousal state (wake/sleep) o MIDBRAIN + HINDBRAIN = BRAINSTEM o Forebrain  Two cerebral hemispheres with an outer surface = cortex  Hemispheres connected by corpus callosum, each has 4 lobe  Hemis good for sensory processing, motor control, higher mental functioning (info processing, learning, memory)  Below hemis = subcortical structures  Thalamus = processing and relaying info between hemi and other parts of CNS  Hypothalamus = regulates basic urges (hunger, thirst, sex)  Limbic system includes hippocampus and amygdala (memory and emotion) Neurotransmission - neurons have three major parts: cell body, dendrites and axon - communication occurs across synapse (gap between cells, synaptic gap or cleft) - electric impulse reach end of axon, neurotransmitters are released - neurotransmitters cross synaptic gap, taken up by receptor sites on dendrites of receiving neuron - receiving neuron generates new electrical impulses - major neurotransmitters: dopamine, serotonin, norepinephrine, glutamate, GABA - neurotransmitters can excite or inhibit neurons/more or less likely to fire an impulse Nervous System, Risk for disordered functioning - nervous system = major aspect of constitutional factors that influence psychological functioning and behaviour - impaired functioning = inheritance or early abnormalities of genetic processes - WIRED IN from beginning - Harm also from events during pregnancy, perinatal (time of birth), postnatal Prenatal influences - poor maternal diet and health - maternal stress alter fetal bio system (including brain) - believed that fetus protected from teratogens (harmful) that might enter mothers bloodstream o drugs = alcohol, tobacco, thalidomide o radiation, environmental contaminants (lead, mercury, PCBs) o maternal diseases = rubella, syphilis, gonorrhea, AIDS - teratogens associated with malformation, low birth weight, fetal death and functional/behavioural impairment o interfere with brain cell formation and migration o amount of exposure = difference in outcome o timing of exposure during gestation - genetic endowment of developing organism can act as risk or protective factor ...regarding effects of teratogen or maternal stress - FAS (fetal alcohol syndrome) o Most severe end , abnormal brain development, retarded growth, birth defects, neurological signs (impaired motor skills, unusual gait) o Facial features: small eyes, thin upper lip, smooth philtrum o Reduced brain volume, malformation of corpus callosum o Psychological difficulties: lower intelligence, cognitive impairments, learning disabilities, hyperactivity and conduct disorder o FACTORS: timing of exposure, amount of exposure, mothers age and health, fetal susceptibility Perinatal and Postnatal Influences - excessive medication given to mother - unusual delivery - anoxia (lack of oxygen) - associated with death and developmental problems (behavioural/academic) o preterm delivery (before 37 weeks) o low birth weight (less than 5.5 lbs) - US overall rate of prematurity = 12% - Lower the birth rate, earlier the delivery = higher the risk - Low birth rate and structural brain abnormalities = infancy to adolescence - Developmental outcome = biological/psychosocial factors too - Postnatal effects = malnutrition, accident, illness, exposure to chemicals o Air pollution, exposure to lead - Plasticity/flexibility of brain to recover from brain damage in youth o Young, immature nervous system = relatively adept at restoring or transferring brain functions o Plasticity especially in vision, audition, motor and language functioning o Brain damage to language areas = less damage in childhood then adulthood, damage to immature brain = neg effects in future o Timing, extent, severity, region of damage, kind/amount of environmental support = factors that influence recuperation Genetic Context - chromosomes containing DNA functional segments called genes - lack or excess of 23 pairs o “errors” may be inherited, many are new - study of genetic influences on individual differences in behaviour is known as behaviour genetics o seeks to establish extent of genetic influence on attributes, discover genes involved, understand how genes operate, reveal paths from genes to characteristics - genetic code = order in which 4 nucleotides (A, T, G, C) appears in gene o critical in determining protein manufacture - sequence is basis for transcription of mRNA o mRNA carries info to other parts of cell, and translates code into protein - each part of gene (exon) codes for protein and larger part = regulatory mech - epigenetics (once applied to embryonic level) now referes to reversible modifications of the genome (regulate gene function) without changing actual gene code o methylation (histones) wrapped in DNA  modifications passed on during mitosis, meiosis, INHERITED  more or less likely gene will be expressed or suppressed o FAS, autism, schizophrenia, intellectual disability - Path from genetic endowment (geneotype) to observable characteristics of the person (phenotype) is indirect Single Gene inheritance - Mendel Gregor - Gene can be dominant (one parent) or recessive (both parents) - Identify person with disorder index case OR proband o Determine whether pattern of single gene inhertitance runs in family Multiple Gene Inheritance - complex human characteristics such as intelligence, psychological disorders - quantitative trait loci (QTL) genes are inherited, each has small influence o combines to create larger effect - less predictable or more probabilistic than single gene inheritance - research into mgi relies on quantitative genetic methods o provide info on contribution of environmental influences and how genes work together  shared environmental influences  influences that contribute to family members developing in similar ways (exposure to intellectual stimulation, environmental toxins, divorce)  nonshared environmental influences  influences that are different for children growing up in the same family (result = siblings different) (differential treatment, different friends or teachers)  credited with having greater influence on psychological and behavioural outcomes !!! o family, twin, adoption studies are important  twin: genetic overlap in language and reading disability  disorders share “generalist” genes (nonshared genes/environmental influences make disorder different)  comparison made between monozygotic twins (share 100% of genes) dizygotic twins share 50%  genetic influence suggested when mono more similar  family studies  evaluate likelihood of family members having similar attributes as the index case  family who are closer to index case should be more likely to display attribute (also consistent with family psychosocial influence)  adoption studies  adopted children with disorder examined in biological family and adoptive family, with bio more genetic influence  OR start with bio parents with disorder and examine rate of disorder in offspring who were adopted by nonrelated families, rate compared to bio children of adoptive parents, higher rate in adopted children = genetic effects o allow for ASSESSMENT OF HERITABILITY - **heritability for psychological disorders rarely exceeds 50% o basis in biological factors, environment or some interplay of genes with these other influences Searching for Genes and their effects: molecular methods - genes associated with disorder, biochemical coded by genes and how biochemicals are involved in behaviour - animals, gene functioning can be knocked out - in humans: - linkage analysis reveals location of defective gene, specific chromosome and place on chromosome o genes on same chromosome , close together, transmitted together to offspring o genetic markers, segments of DNA with known chromosome location, inheritance can be followed o determines whether specific disorder appears among family members in same pattern as a genetic marker  if it does, gene that influences disorder is located on same chromosome as the marker, and is close to marker - association analysis tests whether particular form of a gene is associated with trait of disorder in population o comparison made between disorder and control , focus may be a particular gene “CANDIDATE GENE” (DRD4/DAT1) ADHD o more suitable than linkage to identify multiple genes that have small influence on a disorder or trait - genome-wide linkage / genome-wide association analyses : enable to scan across genomes of individual or large portions , examine millions of DNA sequences Gene-Environment Interplay - gene-environment in
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