Chapter 2

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5 Aug 2010
Chapter 2 - Current Paradigms and the Role of Cultural Factors
Paradigm: A set of basic assumptions, a general perspective, that defines how to conceptualize and study a
subject, how to gather and interpret relevant data, even how to think about a particular subject
The Role of Paradigms
Paradigm: A set of basic assumptions that outline the particular universe of scientific inquiry. It is the
conceptual framework or approach within which the scientist works, according to Thomas Kuhn.
It injects inevitable biases into the definition and collection of data, and may also affect the interpretation of
The meaning or importance given to a data may depend to a considerable extent on a paradigm
The Biological Paradigm
The Biological Paradigm of abnormal behaviour is a continuation of the somatogenic hypothesis (mental
disorders are caused by irregular biological processes)
¾ This paradigm is often referred to as the medical model or disease model
The germ theory (all medical problems are caused by germs, ie. Bacteria and virii) was once very pervasive,
but then it was found that it cannot account for all diseases (ie. Cardiovascular diseases, diabetes, etc.)
All medical illnesses are common in that there is some biological process that is disrupted or not functioning
normally7KLVLVZK\LW¶VFDOOHGWKHBiological Paradigm
This paradigm was dominant from late 1800s to the middle 20th century
Ie. Hall removed ovarian cysts or the whole ovary to treat melancholia, mania, and delusions
Contemporary approaches to the biological paradigm
There is research supporting the claim that heredity factors probably predispose a person to certain
psychopathological problems
¾ Depression may result from a chemical imbalance within the brain
¾ Anxiety disorders may result from a defect within the autonomic nervous system that causes a person to be
too easily aroused
¾ Dementia can be traced to impairments in brain structure
Those working within the biological paradigm assume that the answers to the puzzles of psychopathology will
be found within the body
:HOOORRNDWareas of research within the biological paradigm in which the data are particularly interesting:
behaviour genetics, molecular genetics, and biochemistry
1) Behaviour Genetics
Behaviour genetics is the study of individual differences in behaviour that are attributable in part to
differences in the genetic make up
Genotype: his or her unobservable genetic constitution
¾ Genotype is fixed at birthEXWLVQt static (different genes switch on and off at different times)
Phenotype: the totality of his or her observable behavioural characteristics, such as level of anxiety
¾ Phenotype changes over time, and is a product of the interaction between genotype and environment)
Various clinical syndromes are disorders of the phenotype, not genotype
At most, only the genotype for these disorders can be inherited, but whether these genotypes will eventually
engender these phenotypic behaviour disorder will depend on the environment and experience
A predisposition, also known as a diathesis, may be inherited, but not the disorder itself
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Behaviour genetics has relied on 4 basic methods for whether a predisposition for psychopathology is
¾ 1) Comparison of members of a family
The family method can be used to study a genetic predisposition among family members because the
number of shared genes is known
People who share 50% of genes with a given individual are called first-degree relatives
Nephews and nieces share 25% of an XQFOH¶V genes, and are called second-degree relatives
The starting point for investigations is the collection of a sample of individuals who bear the diagnosis
in question; these people are referred to as index cases or probands
If a predisposition to the disorder being studied is present, first-degree relatives of the index cases
should have the disorder at a higher rate than that found in the general population
¾ 2) Comparison of pairs of twins
Twin studies being with diagnosed cases and then search for the presence of the disorder in the other
When the twins are similar diagnostically, they are said to be concordant
When MZ concordance rate is higher than DZ rate, the characteristic being studied is said to be
%XWVRPHWLPHVWKH GLVRUGHU LVQ¶Wheritable, but rather the children with the disorder could reflect the
child-rearing practices of their disordered parents
Equal environment assumption: the environmental factors that are a partial cause of concordance are
equally influential for MZ and DZ pairs; basically both individuals have to have an equal number of
Sometimes the results may be similar because of the environment rather than biology
¾ Investigation of adoptees
Researchers using this method study children who were adopted seperately
This eliminates the effect of being raised by disordered parents; if both children have an anxiety
disorder, and their parents do as well, this would give support to the claim that a genetic predisposition
figures in the disorder
2) Molecular Genetics
Molecular Genetics tried to specify the particular gene of genes involved in a disorder, and the precise
functions of these genes
Linkage analysis is a method of molecular genetics that is used to study people. Researchers use this method
to study families in which a disorder is heavily concentrated.
It tries to specify the particular gene involved
Researchers collect diagnostic information and blood samples from affected individuals and relatives,
and use the blood sample to study the inheritance patter of characteristics who genetics are fully
understood, referred to as genetic markers
Researchers in this area emphasize gene-environment interactions, which is the notion that a disorder
or related symptoms are the joint product of a genetic vulnerability to specific environmental
experiences or conditions
3) Neuroscience and Biochemistry in the Nervous System
Each neuron has 4 major components: the cell body, several dendrites, one or more axons of varying lengths,
and terminal buttons on the many end branches of the axon(s)
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When it is stimulated through the cell body or dendrites, the nerve impulse (electrical potential) travels down
the axon into the terminal endings
The gap between the sending axon and the membrane of the receiving neuron there is a synapse
The terminal buttons contain synaptic vesicles (filled with NTs; a chemical substance that allows a nerve
impulse to cross the synapse)
The nerve impulse causes the synaptic vesicles to release molecules of their transmitter substances, and these
molecules flood the synapse and diffuse toward the postsynaptic neuron and into their receptor sites
Postsynaptic cell contain proteins (receptor sites), which are sometimes excitatory or inhibitory
The last step is for the synapse to be returned to its normal state (some NT still remains in the synapse)
Sometimes the remaining NTs are broken down by enzymes, or pumped back into the pre-synaptic neuron by
Key Neurotransmitters
¾ Norepinephrine: A NT of the peripheral sympathetic NS, involved in produced high arousal states (thus it
may be involved in anxiety disorders)
¾ Serotonin: A brain NT, may be involved in depression
¾ Dopamine: A brain NT, may be involved in schizophrenia
¾ Gamma-aminobutyric acid (GABA): A brain NT; it inhibits some nerve impulses (may be involved in
anxiety disorders)
Some of the theories linking NTs to psychopathology propose that a given disorder is caused by too much or
too little of a particular NT
Too much or too little of a particular transmitter could result from an error in the metabolic pathways that
produce the NT
The disturbance may also result from a problem in the reuptake process or the number of receptors
¾ The delusions and hallucinations of schizophrenia may result from too much dopamine receptors (increase
in stimulation of the receptors)
Focus On Discovery 2.1: Structure and Function of the Human Brain
The brain is enveloped within 3 layers of non-neural tissues called the meninges;
The brain is divided by a midline fissure into two cerebral hemispheres
The Cerebrum is the thinking part of the brain
Connecting the two hemisphere is the corpus callosum
There are 10-15 billion neurons that make up the grey matter (the thin, outer covering of the brain)
The cortex is vastly convoluted; ridges are called gyri and depressions are called sulci or fissures
Deep fissures divide the brain into 4 lobes: the frontal, parietal, occipital and temporal lobes
Left hemisphere: controls the right half of body, responsible for speech (and some QHXURSV\FKRORJLVWVVD\LW¶V
also responsible for analytical thinking in right handed people, and some left handed people)
Right hemisphere: controls the left half of body, it discerns spatial relations and patterns, is involved in
emotion and intuition
Both hemispheres communicate via the corpus callosum
The grey matter is around the surface of the brain, the interior is mainly white matter (made up of large tracts
or bundles of mylinated fibres)
Nuclei are centres and pockets of grey matter. They serve as connecting tracts from the cortex with other
ascending and descending tracts, and as integrating motor and sensory control centers
4 masses of cortical cells are deep within each hemisphere, collectively called the Basal ganglia
Also deep within the brain are cavities called Ventricles; these are continuous with the central canal of the
spinal cord and are filled with cerebrospinal fluid
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