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THE BIOLOGICAL MODEL. The biological model focuses on mental disorders as diseases. Mental Disorders are viewed as disorders of the central nervous system, autonomic nervous system and endocrine system.

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The biological model


The biological model

  • The biological model focuses on mental disorders as diseases.

  • Mental Disorders are viewed as disorders of the central nervous system, autonomic nervous system and endocrine system.

  • Neither Psychological factors nor a person’s psychosocial environment is believed to play a casual role in the mental disorder.

  • At one time, people belonging to this model hoped to find simple biological explanations of mental disorders but today it is believed that such simple explanations are unlikely to be so simple.

  • Therefore less extreme version of biological viewpoint has emerged and known as biopsychological viewpoint, which allows other casual factors role to be studied in abnormal beh, but primarily focuses on the genetic, biochemical and

The biological model

  • other biological processes which become imbalanced (for whatever reason) and are disrupting normal beh.

  • 6. There are mainly five categories of biological factors which seem to be relevant to the development of maladaptive behaviour A.) Neurotransmitter and harmonal imbalances in the brain. B.) Genetic Vulnerability. C.) Constitutional liabilities. D.) Brain dysfunction and plasticity. E.) Physical deprivation.

  • A.) Neurotransmitter and Hormonal Imbalances

  • If the brain has to work adequately neurons or excited nerve cells should be able to communicate effectively with one another.

  • The site of communication from one neuron to dendrites and to another neuron is the synapse (synaptic cleft) – a tiny filled space b\w neurons.

The biological model

  • The inter neuronal transmission are accomplished by chemicals called neurotransmitters.

  • There are many different kinds of neurotransmitters, some increase the likelihood to produce impulse, while others inhibit impulse.

  • While the neural message has been successfully transmitted to the post synaptic neuron depends on many things such as concentration of certain neurotransmitters within the synaptic cleft.

  • Imbalances in neurotransmitters can result in abnormal behaviour. These imbalances can be due to physiological reasons or psychological stress.

  • Different Ways Of Creating Imbalances:

  • Excessive Production and Release of Neurotransmitter substance into the synapse cause a functional excess in the levels of neurotransmitter.

  • Dysfunction in the normal process of neurotransmitter.

The biological model

Once the neurotransmitters are released in the synapse, they are deactivated. The deactivation occurs in two ways: a.) Once the neurotransmitter substance is released into the synaptic cleft, it is deactivated by enzymes present in the synapse such as monoamine oxidase. b.) Sometime neurotransmitters are reabsorbed or sucked back into the presynaptic axon button, this process is called reuptake.

3. Dysfunction can create neurotransmitter imbalances either when the deactivation enzymes present in synapse are deficient or there is a slowing of the ordinary process of reuptake.

4. There may be problems with the receptors of the post synaptic neuron they can either be abnormally sensitive or abnormally insensitive.

5. Different disorders are thought to stem from the above mentioned imbalance.

The biological model

Neurotransmitters and Psychopathology

Malfunctioning of some Neurotransmitters

NeurotransmittersResulting Problems

Norepinephrine Disrupts emergency reaction in acutely

stressful or dangerous situations.

Dopamine Excessive high levels is associated with


Serotonin Disrupts information processing system

and plays an important role in emotional

disorders such as anxiety, depression

and suicide.

GABA Associated with anxiety disorders

The biological model

Hormonal Imbalances:

Hormones are chemical messengers secreted by a set of endocrine glands in our bodies. Each of the endocrine glands produce and release its own set of hormones which travel through our blood stream and affects parts of our brain and body. Our central nervous system is linked to the endocrine system by the effects of the hypothalamus on the pituitary gland which is the master gland of the body which produces a variety of hormones that regulate or control the other endocrine glands. One important set of interactions occur in the hypothalamic-pituitary-adrenal-cortical axis (hypothalamus receives messages from the central nervous system and dispatches it to pituitary which then stimulates the cortical part of the adrenal gland to produce epinephrine (adrenaline) and the stress hormone cortisole)

The biological model

  • Any kind of malfunctioning of this system gives rise to various forms of psychopathology.

  • Gonadal gland produce sex problems (androgen and testosterone in males and estrogens and progesterone in females )imbalances in which causes maladaptive behaviour. For example :- a girl who was exposed prenatal to high levels of male hormones are likely to show higher levels of tomboyism and a preference for toys usually preferred by boys. (Berenbaum & Itines, 1992)

  • B.) Genetic Vulnerabilities

  • The biochemical processes are themselves effected by genes.

  • Although beh is never determined exclusively by genes substantial evidence show that some mental disorders have a hereditary component.

The biological model

  • Studies have suggested that heredity is an important predisposing causal factor for a number of different disorders, such as depression, schizophrenia and alcoholism (Plomin et al., 1997).

  • Genetic Vulnerability does not manifest itself until later in life i.e.,- adolescence or adulthood.

  • In the field of abnormal Psychology genetic influence rarely express themselves in a simple and straight forward manner. This is because behaviour unlike some physical characteristics such as eye colour, is not determined exclusively by genetic endowment. It is a product of the organism’s interaction with the environment.

  • The subtle influences are transmitted in the genetic code itself but if the genes are faulty or different from normal, they are believed to affect adversely the delicate regulation of brain biochemistry and the result will be maladaptive behaviour.

The biological model


  • PKU Phenylketonuria Excess amount of phenylalanine (a

  • chemical compound in food) and

  • and failure of metabolism of this

  • substance leads to mental

  • retardation and seizures.

  • 2. Lesch Nyhan Syndr- Lethal neurological condition, only

  • -ome ( due to recessive males are affected, shows bizarre

  • gene) behaviour.

  • 3. Tay Sachs Disorder Blindness, too much blinking,

  • (due to recessive movements are affected.

  • genes)

The biological model

  • 4. Huntington’s chorea Due to dominant genes- results in

  • mental retardation, emotional distur-

  • -bance and motor defects.

  • b.) Chromosomal Abnormalities:-

  • The chain like structures with in a cell nucleus that contains genes are called chromosomes.

  • Advances in research have enabled us to readily detect chromosomal abnormalities- irregularities in the chromosomal structure- even before birth.

  • Normal human cells have 46 chromosomes containing the genetic material in which heredity plan is encoded.

  • When fertilization takes place, the normal inheritance consists of 23 pairs of chromosomes, one of each pair from

The biological model

  • the and one from the father.

  • Twenty two of these pairs are called autosomes, they determine by their biochemical action, the general anatomical and physiological characteristics. The remaining pair, the sex chromosomes, determine an individual’s sex. In female, both the chromosomes are X and in male, from mother it is X and from father it is Y chromosome.

  • Research development has shown that abnormalities in the structure or number of chromosomes are associated with wide range of malformation and disorders.


  • Trisomy 13 An extra chromosome in the 13th pair

  • causes a fatal condition with major

  • brain abnormalities.

The biological model

2. Trisomy 18 An extra chromosome in the 18th pair

cause fatal condition related to

severe heart malformation.

3. Trisomy 21 An extra chromosome in the 21th pair

causes down syndrome and results in

mental retardation , slanted eyes and

flattened face.

4. Trisomy 23 An extra chromosome in male causes

klinefelter syndrome resulting in

under developed testicles and lack of

body hair and 20% of them are


The biological model

  • 5. Monosomy 23 A lack of ‘X’ chromosome in female

  • causes turner syndrome resulting in

  • short stature, webbed necks and

  • under developed ovaries.

  • C.) Constitutional Liabilities

  • I. Physical Defects:-

  • Embroyologic abnormalities or environmental conditions operating before or after birth may result in physical defects.

  • Causes Of Physical Defects:-

  • Low birth weight

  • Nutritional deficiencies

The biological model

  • 3. Disease

  • 4. Exposure to radiation

  • 5. Drugs

  • 6. Severe emotional stress

  • 7. Mother’s excessive use of alcohol or tobacco

  • These can lead to :-

  • Learning disorders

  • Behavioural disturbances

  • Emotional disturbances

The biological model


  • It includes reactivity and self regulation. We differ in temperament because everybody has different ways of reacting to a particular stimuli. Temperament is regardedas constitutional rather than genetic because it is probably due to more than genetic influences alone; prenatal and postnatal environmental factors also play a major role in its development. Different temperaments can be affected by

  • Emotional and arousal responses to various stimuli

  • Tendency to approach, withdrew and attend to various situations

The biological model

  • TemperamentLikelihood of developing disorders or

  • developed upto 2 to 3personality characteristics

  • months

  • Fearfulness and Neuroticism– the disposition to

  • irritability experience negative effect.

  • 2. Positive affect and extra version and emotionally positive

  • activity level (Watson et al.,1994)

  • 3. Attentional constraint and control behaviour and

  • persistence show agree able ness.

  • 4. Fearfulness behaviourally inhibited (Kagan 1993,

  • Matheny 1989) Risk is for developing

  • anxiety disorders later on in life.

The biological model

5. Not at all fearful Highly uninhibited behaviour,difficulty

in learning moral values from parents

and society. (Rothbart & Ahadi 1994)

Exhibit aggressive & delinquent

behaviour (Schwartz et al, 1996)

6. No fearfulness Conduct disorder and antisocial

and hostility personality disorder (Harpur, Hart &

Hare 1993)

D.) Brain Dysfunction and neural plasticity:-

Advances in our understanding of how the brain functions and how brain dysfunctions and neural plasticity can lead to psychopathology have been increased at the rapid pace in the

The biological model

  • past decade with the increased availability of sophisticated new neuro imaging techniques to study the function and structure of brain.

  • These and other kinds of techniques to study brain structure and function have been showing that genetic programs for brain development are not as rigid and deterministic as once believed (Nelson and Blum 1977)

  • Important Observations:-

  • Significant damage to brain tissues places a person at risk for psychopathology.

  • The incidence of such damage increases notably among the elderly because of aging process itself, often resulting in Alzheimer’s disease and cardiovascular insufficiency.

  • Brain damage sometimes leads to abnormal beh and also increases vulnerability by making a person less able to cope.

The biological model

4. Genetic programs for brain development are not as rigid and deterministic for example:-

Pregnant monkeys have infants who are jittery and show

exposed to neuro chemical abnormalities and

unpredictable loud increased level of dopamine and

sounds nor epinephrine ( Schneider,1992)

5. Many environmental events that occur postnatally also affect the brain development of the infant and child for example:-the formation of new neural connection or synapse afterbirth is dramatically affected by the experience a young organism has. (Greenough and Black 1992).

The biological model


  • Rats reared in show heavier and thicker cell

  • enriched environment development in certain portions of the

  • cortex (more synapse per neuron).

  • 2.Reared in social show neuro anatomic abnormalities

  • isolation from birth in brain regions that lead to emotional

  • and cognitive malfunction and variety

  • of behavioural and emotional

  • abnormalities (Ginsberg et al.,1993).

The biological model

E.) Physical Deprivation:-


Sleep deprivation for 1. disorientation for time and place

72 to 98 hours 2. feeling of depersonalization.


Sleep deprivation leads 1. performance decreased

to excessive sleepiness 2. performance lapses

3. vulnerability to accidents

4. use of caffeine and alcohol

5. mood and behavioural problem

The biological model

Food Deprivation Psychological Impact and problems

Prolonged food 1. Dramatic personality and behavioural

Deprivation changes.

2. Irritable, unsociable, unable to

concentrate on or day dream about

food only, lying and stealing food.

3. After six months the predominant

mood was of gloom and depression

accompanied by apathy, feeling of

inadequacy and loss of interest in


The biological model

Severe malnutrition 1. Impairs physical development.

Associated with 2. Lower resistance to disease.

Prenatal neglect 3. Stunts brain growth markedly

Limited access to lowered intelligence .

Health care 4. Risk for disorders such as

attention deficit disorder.

5. Attentional problems.

6. Increased distractibility and

interference with school


The biological model


  • Healthy mental development depends on a child’s receiving adequate amount of stimulation from the environment.

  • Physical development of the brain is adversely affected by an unstimulating environment.

  • Enhanced biological development depends on enriched and complex environment where the child is engaged in different activities in early stages of development.

  • On the other hand, there are limits to how much stimulation is beneficial to a developing organism.

  • Though we don’t have much evidence, but sensory overload can impair functioning. As we all know that under excessive pressure we may strive to decrease the level of stimulation. On the other hand under some conditions such as boredom-we may strive to increase the level of stimulation by doing something.

The biological model

  • 6. So it is important to have an optimal level of stimulation and activity for normal psychological functioning.


  • Merits:-

  • This model has affected the way we think about human behaviour.

  • We now recognize the important role of bio chemical factors and innate characteristics and their effect on normal and abnormal behaviour.

  • Due to this model, we have witnessed many new development in the use of drugs, that can dramatically alter the severity and course of certain mental disorders, particularly the more severe ones like schizophrenia.

  • The host of new drugs brought a great deal of attention to

The biological model

  • the biological model, not only in scientific circle but also in the popular media.

  • 5. Biological treatments based on this model have immediate results and they have provided the hope that in most cases, biological therapies will lead to “cure all”- immediate results with seemingly little effort.

  • Demerits:-

  • It will be a mistake to emphasize this model only. It will be useful if used with other models and there are several common errors in a way people interpret the biological advances.

  • No direct link between biological causes and mental disorders are found, the relationship is complex.

  • If we find biological base for any disorder, we say that the person is ill but in this way our personality traits have also biological base, then are they reflect our illness.

The biological model

4. It will be difficult to separate the biological factors from environmental factors totally.


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