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Physiological Psyc Chapter 1
Physio Psyc Defined • The study of the physiological, evolutionary, and developmental mechanisms of behavior and experience. Much of biological psychology is devoted to studying how the brain functions. The term “biological psychology” emphasizes that the goal of this field is to relate biology to issues of psychology. In comparison the field of neuroscience includes much of the same content but with more emphasis about chemistry and anatomy.
Biological explanations of behavior • Physiological explanations: Relates behavior to the activity of the brain and other organs. Deals with the machinery of the body. • Ontogenetic explanations: Describes the development of a structure or a behavior. Looks at the influence of genes, nutrition, experience and the interaction among these influences on behavior.
Biological explanations of behavior • Evolutionary explanations: Examines a structure or a behavior in terms of evolutionary history. Examines the continuity (unbroken course) of a behavior from past ancestors to the present. • Functional explanations: Describes why a structure or behavior evolved as it did. Looks for the benefit or advantage for having certain behaviors.
Career Opportunities • Careers in biological psychology fall into two categories—research and therapy • Research positions require a PhD in psychology, biology, neuroscience, or related field and may be in academic, government or industrial settings.
Career Opportunities • Fields of therapy include clinical psychology, counseling psychology, school psychology, several specializations of medicine and allied medical practice such as physical therapy.
Mendelian Genetics • During the nineteenth century, Gregor Mendel demonstrated that inheritance occurs through genes (units of heredity that maintain their identity from one generation to the next). • As a rule, genes come in pairs as they are aligned along chromosomes (strands of genes). One exception to this rule is male sex chromosomes which do not come in pairs.
A gene is a portion of a chromosome, which is composed of a double-stranded chemical called deoxyribonucleic acid (DNA). • A strand of DNA serves as a template (model) for the synthesis of ribonucleic acid (RNA).
RNA is a single-stranded chemical: one type of RNA serves as a template for the synthesis of protein molecules. • Proteins can be part of the structure of the body or serve as enzymes (biological catalysts that regulate chemical reactions in the body).
If individuals have an identical pair of genes on the two chromosomes, they are homozygous for that gene; if they instead have an unmatched pair of genes, they are heterozygous for that gene (e.g., a gene for black hair on one chromosome and a gene for brown hair on the other).
Certain genes can be identified as dominant or recessive. Dominant genes show a strong effect in either homozygous or heterozygous conditions; recessive genes show their effects only in homozygous conditions (e.g., a carrier for both a black hair gene dominant and a brown hair gene (recessive) will have black hair).
Typically the inheritance of one gene is independent to inheritance of another gene. However, genes on the same chromosome are linked and their inheritance is not independent
Crossing over is an exception to the linkage of inheritance of genes on the same chromosome where chromosome pairs will break apart and reconnect to each other during reproduction.
Sex-Linked and Sex-Limited Genes • Genes located on sex chromosomes are known as sex-linked genes. All other chromosomes are referred to as autosomal chromosomes. Genes located on autosomal chromosomes are autosomal genes.
A female mammal has two X chromosomes; a male has one X and one Y chromosome. • The Y chromosome carries the gene which causes the person to develop as a male; the X chromosome carries many genes (these are usually referred to as sex-linked genes).
Sex-linked recessive genes have their effects only in the absence of the dominant gene. • Sex-limited genes: Genes present in both sexes but mainly or exclusively has effects in one sex. The differential effect is because these genes must be activated by sex hormones.
Sources of Variation • Evolution is only possible when variation exists. Two common sources of variation are recombination and mutation.
Recombination: A new combination of genes that occurs during reproduction. • Mutation: A random change in a single gene; most mutations produce recessive genes.
Heredity and Environment • Heritability is an estimate of how much of the variance in some characteristic is due to heredity. Heritability ranges from 0 to 1. A heritability of 1 indicates that heredity is responsible for all observed differences; a heritability of 0 indicates heredity is responsible for none of the observed differences.
Heritability in humans is studied in two ways. First by comparing monozygotic (identical) twins and dizygotic (fraternal) twins. Second, by comparing adopted children and their biological parents. • Environmental influences may affect traits with high heritability (eg. PKU)
Phenylketonuria (PKU): A genetically caused form of mental retardation that can be avoided with a strict diet that prevents build up of phenylalanine). • Genes affect behavior through the proteins they produce and their influence on specific body systems.
Evolution of Behavior • Evolution: Change over generations in the frequencies of various genes in a population. • Offspring generally resemble their parents, but because of mutations and recombinations new inheritable variations in the gene pool can occur.
Artificial-selection: Breeding animals for desirable individual characteristics (this causes changes in various genetic frequencies in a population).
Misconceptions in evolution: • Lamarckian evolution: Use or disuse of some structure or behavior causes an evolutionary increase or decrease in that feature. • Humans are no longer evolving because of modern medicine and prosperity.
Evolution necessarily improves the fitness (the number of copies of one’s genes that endure in later generations) of the population. • Evolution acts to benefit the individual or the species.
Altruisticbehavior • Behaviors that benefit others rather than the individual committing the behavior. This is in contrast to the belief that genes evolve for their own benefit.
If altruistic genes exist, they may spread through reciprocal altruism (the notion that animals help those that help themselves) or kin selection (selection in favor of a gene because it benefits the animal's relatives).
Sociobiology a.k.a. evolutionary psychology • The study of the relationship between social behavior and evolutionary theory; sociobiologists emphasize functional explanations of behavior (how a behavior may be useful to a population and why natural selection would favor it).
Reasons why biological psychologists study animal behavior • The underlying mechanisms of behavior are similar across species (especially mammalian) and are often easier to study in nonhuman species. • We are interested in animals for their own sake.
Reasons for using animalsCont’d • What scientists learn about animals sheds light on human evolution. • Certain experiments cannot use human subjects because of legal or ethical restrictions.
Researchers in biological psychology realize that using animals in experiments is necessary for acquiring knowledge about behavior but may indeed be painful to their subjects. Therefore investigators often look for compromises when conducting animal research to reduce the suffering of animals.
Research careers (requiring a Ph.D.) • Behavioral neuroscientist (psychobiologist, biopsychologist, physiological psychologist): Investigates how functioning of the brain and other organs influences behavior.
Neuroscientist: Studies the anatomy, biochemistry, and physiology of the nervous system. • Neuropsychologist: Conducts behavioral tests on people with brain damage or brain diseases to determine what the person can and cannot do and to monitor improvement or deterioration over time.
Psychophysiologist: Measures heart rate, breathing rate, brain waves, and other body processes that change as a function of what someone is doing or what kind of information the person is processing.
Comparative psychologist (ethologist, animal behaviorist): Compares the behaviors of different species and tries to relate them to evolutionary histories and ecological niches.
Sociobiologist (evolutionary psychologist): Relates behaviors, especially social behaviors, to the functions they have served and, therefore, the presumed selective pressures that caused them to evolve.
Related medical specialties (requiring a MD) • Neurologist: Treats people with brain damage or diseases of the brain. • Neurosurgeon: Performs brain surgery. • Psychiatrist: Helps people with emotional distress or troublesome behaviors, sometimes using drugs or other medical procedures.
