Models of Abnormal behavior Naomi Wagner, PhD

Categories of Explanations of Abnormal Behavior Biological: genetics, brain anatomy, biochemical imbalance, central nervous system, etc Psychological: Emotions, thoughts. Personality, learning Social: issues with relationships Sociocultural: norms for behavior, expectations, cultural climate

What is a Model? Etiology: Model: Cause or origin of a disorder Model: An analogy used by scientists, usually to describe or explain a phenomenon or process they cannot directly observe Model, viewpoint, and perspective are often used interchangeably A multipath model considers interactions among all possible layers of causes

Models (cont-d) These one-dimensional views are overly simplistic: Set up a false “either-or” dichotomy between nature and nurture Fail to recognize the reciprocal influences of one on the other Mask the importance of acknowledging the contributions of all four dimensions in the origin of mental disorders

The Biopsychosocial Model Interaction between the possible causes Multiple pathways to any disorder Not all causes contribute equally to a disorder People exposed to the same factors may not develop the same disorder People exposed to different factors may develop similar disorders

The Structure of the nervous System

The Structure of the Nervous system The Central Nervous System: The brain and spinal cord The Peripheral Nervous System: A. The Somatic NS B. The Autonomic NS (sympathetic and para-sympathetic.)

Neural Transmission How is information transmitted in the brain Neurons are separated by a gap (synapse) The neurons “communicate” at the synapse Neuron structure: dendrite, cell-body, axon Electrical signals are transmitted chemically across the synapse The signals stimulate the “pockets” at the tip of the axon to release neurotransmitter

Cont-d Electro- chemical transmission The signal stimulates the vesicles Vesicles release the neurotransmitter into the synapse Neurotransmitter: Chemical substance released from a neuron into the synaptic cleft it drifts across the synapse and is absorbed by the receiving neuron The signal “floats” on the neurotransmitter to the next neuron Neurons form inter-connected pathways

Cont-d The neurotransmitters can either excite or inhibit the neuron receiving the signal The activity of the neuron depends on the balance between “on” and “off” signals Serotonin is implicated in depression and the OCD. Dopamine is implicated in schizophrenia (too much) and Parkinson (too little) GABA (an inhibitory) is implicated in anxiety

Biochemical Theories Basic premise: Dendrites: Axons: Chemical imbalances underlie mental disorders Dendrites: Receive signals from other neurons Axons: Send signals to other neurons

Neural Transmission

Selected Neurotransmitters Involved in Some Mental Disorders

Abnormalities in Brain Structure It is not always possible to connect brain structures to psychological symptoms researchers believe that abnormally developed brain structures In 1848 an explosion during the paving of a rail road caused a metal rod to pierce Phineas Gage eye socket and to enter his brain As a result he showed significant changes in personality

The Human Brain

Functions of the brain The forebrain: Controls all the higher mental functions, such as learning, speech, thought, and memory Thalamus: “Relay station;” transmits nerve impulses throughout brain Hypothalamus: Regulates bodily drives and body conditions Limbic system: Involves experiencing and expressing emotions and motivation

Cont-d The midbrain: The hindbrain: Involved in vision and hearing, and along with the hindbrain, controls sleep, alertness, and pain Manufactures serotonin, norepinephrine, and dopamine The hindbrain: Controls heart rate, sleep, and respiration Manufactures serotonin

Genetic Influences Each cell of our body contains 46 chromosomes They are made of DNA our genetic material A gene is a segment of DNA along the length of the chromosome that contain the instructions for forming proteins which in turn determine how the cell works Proteins are the building blocks of our body

Human Chromosomes

Genetics (cont-d) Genetic abnormalities can come about through: Inheritance of particular combinations of genes Faulty copying when cells reproduce Mutations that a person acquires over the course of life Cells possess the ability to repair many of the mutations The 46 chromosomes are arranged in 23 pairs One chromosome from mother and one from father

Genetics (cont-d) Genetic makeup plays an important role in developing abnormal conditions Autonomic nervous system reactivity may be inherited Hereditary factors are implicated in alcoholism, schizophrenia, and depression

What do genes do? Genes control the manufacturing of neurotransmitters as well as the way the neurotransmitters behave at the synapse Genes also determine how the brain structures develop throughout life Any factor that can alter the genetic code can alter how those structures perform

Genotype and Phenotype The 46 chromosomes are arranged in 23 pairs Twenty-two of the pairs are identical (the 23rd pair is the sex chromosomes XX and XY ) It means that the same gene is located in the same place on each of the chromosomes Two forms of the same gene are called alleles The Genotype is the overall genetic makeup The Phenotype is the expression in your physique and psychological attributes

Dominant Recessive Relationship The Alleles are related to each other in Dominant- Recessive relationship a dominant allele prevails over a recessive allele However, human characteristic and psychological disorders are polygenic- more than one gene participates in determining a given characteristic Epigenetics is the attempt to understand how the environment affects genes to produce genotypes

PATTERN OF DOMINANT-RECESSIVE TRAIT INHERITANCE

Genes-environment Interactions Interactions between genes and the environment Passive exposure: Children are exposed to environments that their parents create based on the parents’ genetic predisposition The child’s genetically- based traits elicits responses from the environment Niche-Picking: the child seeks out an environment that gratifies his/her genetically- based inclinations

Diathesis-Stress Model Proposal that people are born with a predisposition that places them at risk for developing a psychological disorder if exposed to certain extremely stressful life experiences.

Assessment of Genetic Factors Family inheritance studies: Researchers compare the disorder rates across relatives who have varying degrees of genetic relatedness Usually comparing Identical twins who share 100% of their genes to Fraternal twins who share 50% of their genes Studies comparing parents and children are confounded because of possible environmental effect

Biologically- Based Therapies Psychopharmacology: Study of effect of drugs on mind and behavior Electroconvulsive therapy: Application of electric voltage to the brain to induce convulsions Psychosurgery: Brain surgery for the purpose of correcting a severe mental disorder